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Mate guarding, reproductive success and female choice in African elephants
Abstract
Male guarding of females, male mating success and female choice were studied for 8 years among a population of African elephants, Loxodonta africana. Males were not able to compete successfully for access to oestrous female until approximately 25 years of age. Males between 25 and 35 years of age obtained matings during early and late oestrus, but rarely in mid-oestrus. Large musth males over 35 years old guarded females in mid-oestrus. Larger, older males ranked above younger, smaller males and the number of females guarded by males increased rapidly late in life. Body size and longevity are considered important factors in determining the lifetime reproductive success of male elephants. Oestrous females exercised choice by soliciting guarding behaviour from musth, but not non-musth males. Females in mid-oestrus gave loud, very low frequency calls that may attract distant males and incite male-male competition. The behaviour of oestrous females resulted in their mating with males who were old, vigorous and healthy.
... Selection against aggression has been proposed, among other mammalian groups, for the families Hominidae (bonobos: Pan paniscus; humans: Homo sapiens) and Elephantidae, including African savannah elephants (Loxodonta africana), forest African elephants (L. cyclotis), and Asian elephants (Elephas maximus) (Hanks, 1979;Poole, 1989;Raviv et al., 2023). In African elephants-living in fission-fusion societies with core family units of related females and offspring-low aggression might stem from several strategies. ...
... Our results indicate that social play dynamics may be overall consistent with selection against aggression in African savannah elephants (Hanks, 1979;Poole, 1989;Raviv et al., 2023). Indeed, we found that social play (and not affiliation and aggression) decreased with age, and that it persisted (as affiliation and aggression) in adulthood (Prediction 1a confirmed; Table 2; Figures 3, 6A and 6B). ...
... Further investigation on a larger sample is necessary to either corroborate or reject this possibility. Overall, our results are in line with previous findings showing that in African savannah elephants social play, especially in subadult-adult males, can move from non-aggressively testing others' physical abilities and establish/reinforce dominance to cementing social bonds (Poole, 1989;Lee and Moss, 2014). The flexible use of social play in African savannah elephants is consistent with selection against aggression, as neurobiologically and ecologically, social play be used in subadult/ adult mammals as a non-aggressive coping mechanism when aggression is reduced or inhibited, in response to arousal or stressful situations, or as substitute for aggression (Beatty et al., 1982;Behncke, 2015;Blois-Heulin et al., 2015;Cordoni et al, 2021;Potegal and Nordman, 2023). ...
In social groups, competition for individual advantage is balanced with cooperation, for the collective benefit. Selection against aggression has favoured cooperation and non-aggressive competitive strategies. Because social play is a behavioural system that fluctuates between cooperation and competition, selection against aggression might have especially influenced this behaviour. African savannah elephants (Loxodonta africana) are a low aggressive species, therefore suitable to investigate this aspect. We collected all occurrences observational audio-video data on social play, aggression/threats, and affiliation on an African elephant colony housed in a 25-ha open space at Parque de la Naturaleza de Cabarceno (Cantabria, Spain) and composed of four family groups (3 immature males, 3 immature females, and 7 adult females) and two adult males. Anticipating the influence of reduced aggression, we found that social play decreased with age, persisting in adults, and that it was highest in males. Social play was associated with affiliation (informing cooperation). Indeed, individuals that were central in the social play network were also central in the affiliation network. For immature subjects, we found a correlation between social play and affiliation sociomatrices. However, such correlation was absent in adults and social play mostly occurred between families. Despite the limitations related to dealing with a small captive group, this study largely supports the idea that the features of social play in African savannah elephants may be related to low aggression. This investigation hints toward a non purely cooperative use of play, possibly as a non-aggressive interaction that accommodates different levels of cooperation and competition.
... African elephant calves' development is subdivided into seven stages, as listed in Table 1 [4][5][6][7][8][9][10]. Calves in zoos possibly undergo the same developmental stages and are described by Andrews et al. [11], Webber [12], and Freeman et al. [13]. ...
... Females start to show ovarian cycles at 6 to 7 years and can give birth for the first time at 8 to 9 years [16]. While data on the onset of the ovarian cycle in wild females are missing, the first births are reported in cows mostly between 12 and 16 years of age, the earliest being reported at 9 years old (± one month) [9,10,17,18]. Males in zoos must not show musth to be able to breed [19] and can sire offspring as young as 9 to 10 years old [19]. Whereas in the wild, males reach musth for the first time around the age of 12-14 years and were observed to be accepted as mating partners by cows only at the age of 25 years [10]. ...
... Males in zoos must not show musth to be able to breed [19] and can sire offspring as young as 9 to 10 years old [19]. Whereas in the wild, males reach musth for the first time around the age of 12-14 years and were observed to be accepted as mating partners by cows only at the age of 25 years [10]. ...
Simple Summary
In the wild, African elephant calves must stay close to their mothers and the family unit as the African environment holds many threats. African elephant calves in zoos are raised in a protected environment. Therefore, we hypothesize that calves ex situ hold bigger distances and behave differently than in situ. Additionally, those differences are likely to increase with further zoo generations. This study used ethological research methods to compare the mother–calf bond of African elephant calves in situ and ex situ (first and second generation). The results showed that ex situ living calves of both generations maintain greater distances to their mothers and show a wider variation (positive and negative) in behavior than in situ. The detected differences indicate that calves ex situ can behave more freely as they are in a protected environment. Therefore, they can develop faster than in the wild, which agrees with similar findings on African elephant calf development and adult African elephants. The hypothesis that differences between in situ and ex situ increase with the zoo generations could not be verified. Hence, modifications in behavior under different environmental selection pressures may be adaptive.
Abstract
African zoo elephants live in safe environments with sufficient resources, are protected from threats, and have their health and body conditions cared for. Calves ex situ undergo the same developmental stages as in situ and are raised by the whole family unit. However, due to environmental differences, there might be behavioral modifications between calves in situ and ex situ. We hypothesize that these differences increase with ongoing generations. This ethological study compares social and general behavior and the distance calves kept to their mothers’ between calves of the first (F1) and second (F2) zoo generation and the wild. Using ethological methods, data were collected for ~90 in situ calves and 16 ex situ (8 F1, 8 F2) between the ages of 0.5 to 4 years (120 observation hours per group). Results showed that in situ calves spent significantly more time close to mothers than the F1 and the F2 zoo generations (F1/in situ: p = <0.001; F2/in situ: p = 0.007). The behaviors of eating, drinking, trunk movement, washing, and affiliative behaviors showed significant differences between in situ and ex situ calves. The amount and distribution of affiliative and agonistic behavior initiated and received by calves was displayed with a greater variety ex situ. Ex situ calves not only performed affiliative but, in contrast to the in situ, also agonistic behavior (F1/in situ: initiated p = 0.002, received p = 0.010; F2/in situ: initiated p = 0.050, received p = 0.037). The comparison of zoo generations suggests that differences did not increase with the generation. The more casual binding between mothers and offspring in zoos and the age-dependent improvement of social behavior of zoo-born calves are seen as a result of elephants’ adaptation to secure zoo conditions. The results of this study agree with the faster development of ex situ African elephants, like earlier puberty and more frequent breeding patterns, as known from the literature.
... Moreover, family groups occupy areas beyond the confines of wildlife preserves all across the African continent [16,17,22,25]. These factors drive musth males to travel farther, faster, and with more directional purposes [11,[26][27][28][29][30]. As a result, elephants that are sexually active or in musth may enter unprotected areas adjacent to wildlife parks where human-elephant conflict (HEC) continues to intensify [20,31,32]. ...
... Adult female elephants only enter into estrus every four-five years due to lengthy gestational and postpartum lactation periods that prolong inter-calving intervals [12,58,59]. Moreover, peak estrus in female African elephants only lasts two-three days [27,60], making it imperative that males recognize a female's reproductive status and locate her across vast landscapes. To signal their reproductive status and attract males, estrous females engage in distinctive behaviors [58], emit characteristic estrous roars when chased [61] and, during peak estrus, produce a series of low-frequency estrous rumbles immediately after mating [27,30,52,62]. ...
... Moreover, peak estrus in female African elephants only lasts two-three days [27,60], making it imperative that males recognize a female's reproductive status and locate her across vast landscapes. To signal their reproductive status and attract males, estrous females engage in distinctive behaviors [58], emit characteristic estrous roars when chased [61] and, during peak estrus, produce a series of low-frequency estrous rumbles immediately after mating [27,30,52,62]. These low-frequency estrous calls can propagate on the order of several kilometers and are likely to be heard by many elephants [56,63]. ...
Driven by reproductive motives, male African elephants (Loxodonta africana) in musth often expand their home ranges to locate estrous females. This extended range, coupled with heightened aggression often observed in musth males, can be particularly problematic in regions where human-modified landscapes and elephant territories increasingly overlap. Several mitigation tools have been tested to resolve a wide range of human–elephant conflicts with varying degrees of success due to geographical disparities and habituation. We present findings on the potential application of estrous call playbacks in manipulating the behavior and movement of male elephants non-invasively, particularly mature musth adults and younger post-dispersal males, in Etosha National Park. Estrous vocalizations were presented across 26 experimental trials to mature musth adults (n = 5), mature non-musth adults (n = 6), and non-musth males belonging to younger, post-dispersal age classes (n = 8), with behavioral responses scored on a gradient scale from 0–1. Both mature musth adults and younger non-musth elephants were significantly more likely to respond with the highest intensity by approaching the acoustic source compared to mature non-musth adults that avoided the call. However, younger males tested in the presence of an older, higher-ranking male tended to react with a lower intensity than those tested alone. This result likely demonstrates the influence of social hierarchy and associations on male elephant behavior. We also observed a significant increase in physiological response, measured by defecation rate, across all male groups in response to the estrous call playbacks. Our findings suggest that using estrous calls as acoustic deterrents may effectively and non-invasively aid in reducing tension at the human–elephant interface, depending on the age, social context, and reproductive status of the male elephant.
... However, similar to any other sexually selected trait, the occurrence of musth should be linked to variation in reproductive success (Hosken & House, 2011). Elephants are polygynous and do not defend distinct territories, nor do adult male elephants typically associate with females beyond the period of oestrus (Poole, 1989b;Ganswindt et al., 2005b;Vidya & Sukumar, 2005;de Silva & Wittemyer, 2012). Therefore, it is unlikely that females choose to mate with musth males as a result of a direct benefit, such as parental care, protection, or access to resources within a territory (Møller & Jennions, 2001;Jones & Ratterman, 2009). ...
... Females preferentially associate with musth males, which leads to more successful mating attempts by these males (Poole, 1989b;Chelliah & Sukumar, 2015). In long-lived species with prolonged interbirth intervals, only long-term studies can answer if these intersexual associations and mating attempts lead to increased paternity success . ...
... However, given the continued controversy of the Handicap Principle in its varied forms (Penn & Számadó, 2020), a re-evaluation of musth in a Darwinian framework would be valuable. From musth's first scientific descriptions, biologists have hypothesised about its value to female mate choice (Eisenberg et al., 1971;Eisenberg, 1980;Hall-Martin, 1987;Poole, 1989b), and the process of mate choice is critical for intersexual selection to occur. Sexual selection theory posits that the selection for sexual traits (such as musth) results from the balance between a mating advantage and increased risk of mortality. ...
Sexual selection mediated by multimodal signals is common among polygynous species, including seasonally breeding mammals. Indirect benefit models provide plausible explanations for how and why mate selection can occur in the absence of direct benefits. Musth-an asynchronous reproductive state in male elephants-facilitates both inter-and intrasexual selection via indirect benefits, and it is further communicated through a multimodal signal. In this review, we synthesise existing evidence that supports the hypothesis that musth is a multimodal signal subject to sexual selection and that male elephants increase their direct fitness by propagating this signal while females accrue indirect benefits. Musth is characterised by a suite of physiological and behavioural changes, serving to facilitate copulation between the sexes, and via multisensory modalities musth conveys honest information about the condition of a male. Female elephants mate preferentially with musth males, increasing their own fitness in the absence of direct benefits. In addition, musth resolves dynamic dominance hierarchies among male elephants and often eliminates the need for costly physical combat. Future work in this field should investigate potential postcopulatory selection mechanisms in elephants, including sperm competition and cryptic female choice. These topics join other fundamental questions related to sexual selection, signalling, and indirect benefits that are still unanswered in elephants.
... There is preliminary genetic evidence that dispersal is not random, and groups of adolescent bulls are related to one another (Vidya & Sukumar, 2005;Chiyo et al., 2011). Greeting and sparring with similar-aged males, both familiar and unknown, enables an individual bull to assess his position in the hierarchy, develop social skills and gain knowledge about possible future opponents with whom he will compete for access to females (Poole, 1989;Beacham, 2003;Evans & Harris, 2008). Adolescents also associate with older bulls, presumably to gain knowledge about the environment, the location of forage, and to learn appropriate social and reproductive behaviours (Rees, 2004;Chiyo et al., 2011;Goldenberg et al., 2014). ...
... The phenomenon of musth is unique to bull elephants; it is a period of intense sexual activity characterized by high testosterone levels, urine dribbling and temporal-gland secretion (Poole & Moss, 1981;Poole, 1987). Musth confers a breeding advantage to sexually mature bulls: oestrous females select musth bulls as mating partners and mating success increases after males have experienced their first period of musth (Poole, 1989;Hollister-Smith et al., 2007). During musth, gonadally derived testosterone, and its physiologically active metabolite dihydrotestosterone, increase dramatically, often rising tenfold or more above baseline levels (Yon et al., 2007). ...
... Bulls come into musth asynchronously (Poole, 1987) and each bull has his own annual musth cycle. This has the added benefit that potential conflict between bulls is avoided, as bulls in musth will suppress other bulls both socially and sexually (Poole, 1989;Slotow et al., 2000;Evans & Harris, 2008;Wyse et al., 2017). Musth bulls display a wide range of physical, acoustic, olfactory, chemical and behavioural signals to communicate their status to cows as well as to other bulls (Poole & Moss, 1981;Vidya & Sukumar, 2005), and often show aggressive behaviour, both to conspecifics and to other animals in the landscape (Poole, 1989). ...
In the wild, bull elephants socialize with conspecifics of all ages and both sexes, and young bulls develop social bonds with other elephants which will be sustained throughout their lives. Significant progress has been made towards providing an environment that facilitates social behaviour and multi‐generational family structure for female elephants in zoos. However, it is more complex and challenging to build facilities and manage groups of elephants in ways that allow fission–fusion herd dynamics and give the elephants choice over their environment. For bulls, this is further complicated by their potential strength and aggressive behaviour. To advance the development of best‐practice management for zoo elephants and achieve high standards of welfare, it is necessary to improve our understanding of the social and behavioural needs of bull elephants, and implement radical and innovative solutions to their care. In this paper we (1) consider how the social behaviour of bull elephants is addressed in zoos, comparing their social management with their behaviour in the wild, (2) contribute novel preliminary data about how these issues are addressed, and (3) propose some new approaches to the management of bull elephants in zoos for the future.
... Although poaching for ivory concentrates on single adult males (Gobush et al., 2008), poachers also target female matriarchs as they also have large tusks and are easier to find than solitary males (Poole, 1989). Poaching disrupts kin-based association patterns, decreases the quality of elephant social relationships, and increases male reproductive skew, with significant consequences for population health and the maintenance of genetic diversity (Archie & Chiyo, 2012). ...
... Poaching targets large individuals for their higher tusk sizes (Mondol et al., 2014). Although poaching for ivory primarily targets single adult males (Gobush et al., 2008), poachers also target female matriarchs as they also have large tusks and are easier to find than solitary males (Poole, 1989). Selective removal of larger adult males and females from elephant populations affects age and sex structure. ...
... In contrast, most populations of African elephants outside the Serengeti experienced a rapid decline. Populations that have experienced heavy poaching tend to have skewed adult sex ratio in favor of females, (Poole, 1989) lower OSR and a higher proportion of tuskless individuals . Given the fact that the SNP is experiencing the opposite of what is happening in most other areas of Africa, we do not expect the adult sex ratio to deviate significantly from 1:1. ...
African savanna elephants (Loxodonta africana) are ecologically important as ecosystem engineers and socio-politically as revenue earners for national economies and local communities. However, their population has declined due to poaching and loss of habitat as a result of an increase in the human population. Habitat loss and fragmentation makes most protected areas isolated because of blocking of wildlife corridors. This study covered four ecosystems (Serengeti, Tarangire-Manyara, Selous, and Ruaha) in Tanzania which have the largest elephant populations in the country to determine the extent of genetic diversity and population structure nuclear and mitochondrial DNA markers. We wanted to establish historical genetic connectivity using mitochondrial DNA and contemporary gene flow using microsatellite markers from DNA obtained non-invasively from fecal samples. We specifically wanted to determine if there is gene flow between the Serengeti and Tarangire-Manyara ecosystems and whether the genetic structure has substantially changed over the past 50 years. We assumed that the Greater Rift Valley between two ecosystems would also act a barrier to the gene flow. We collected 800 elephant fecal samples from the four ecosystems and performed genetic analyses at the Pennsylvania State University. Our results showed that the Serengeti elephants are genetically distinct from the Tarangire-Manyara. Elephants from Ngorongoro showed an admixture between the two ecosystems. We also identified that there was a higher genetic similarity of elephants between Ngorongoro and Lake Manyara compared to Lake Manyara and Tarangire. Also, Tarangire and Ruaha elephants shared the same population structure although they are more than 400 km apart. Within the Serengeti ecosystem, we identified two population clusters from south and north of the Serengeti. Our results suggest that even without any physical barriers, there is genetic differentiation. The analysis of nuclear and mitochondrial DNA showed significant population differentiation between the Ruaha and Selous ecosystems. We further found no evidence for female-mediated gene flow between Ruaha and Selous. Only 4% of elephants sampled in Ruaha shared a haplotype with the Selous Game Reserve.We also developed a novel fecal-centric approach to assess the age and sex structure of elephants and validated it with a rapid demographic assessment. We compared the sex ratio of elephants between Serengeti National Park, Ngorongoro Conservation Area and Maswa Game Reserve which have different protection status. In Serengeti, the sex ratio for adult age classes was skewed in favor of females whereas, in Ngorongoro, the sex ratio was skewed in favor of males for elephants older than 25 years. Although poaching is the main explanation for the observed sex ratio in Serengeti, we speculate that differential survival rates between males and female could explain the differences in sex ratio, particularly for young elephants. Our findings provide baseline information about historical connectivity using the mitochondrial DNA and recent gene flow (using nuclear markers) between protected areas in Tanzania. This information may be used to inform laws to protect the existing wildlife corridors or to restore the blocked corridors. We have highlighted some wildlife corridors that may have been or are still very important for the elephants based on our data; these would be suitable targets for conservation and restorations
... Our findings suggest that with the identification method biased towards highly distinctive (D ≥ 4) individuals, the strength and variation of female elephant associations are significantly underestimated. This is because the generally weak associations between females and distinctive adult males (Poole, 1989;Goldenberg et al. 2014;Chui 2021) were overrepresented and-more importantly-the complex intra-and inter-sex social interactions of female elephants, i.e., associations among females in the multitiered hierarchal society (Moss and Poole 1983;Wittemyer et al. 2005) and their interactions with post-dispersal young males (Chui 2021) are underrepresented. ...
... Individuals with mismatched results of permutation tests of mean A.I. did not necessarily have mismatched permutation results of the SD of A.I. and vice versa, suggesting that the effect varies among and between sexes, and is possibly individual-specific. This can be attributed to their highly complex social dynamics, where the social interactions between individuals can be influenced by kinship (Archie et al. 2006;Chiyo et al. 2011), age (Evans and Harris 2008;Chiyo et al. 2011), associative learning (Archie et al. 2006), social status (Wittemyer et al. 2007;Evans and Harris 2008), reproductive state (Poole 1989;Goldenberg et al. 2014), resources and competition (Wittemyer et al. 2005). Nonetheless, the exclusion of less distinctive individuals (as in EB dataset) seems to have more pronounced impacts on the estimated strength of female associations (mean A.I.) and male pattern of preferred/avoided associations (SD of A.I.), with 36.7% of females (Fig. 10a) and 33.3% of males (Fig. 10b) displaying mismatched results between datasets. ...
Reliable identification of individuals plays an important role in behavioural studies of free-ranging animal populations. In field studies of elephants, the naturally acquired markings on their ears, such as notches, tears and holes, are frequently used for individual identification. Although not as easily discernible from a distance as ear markings, the facial wrinkle pattern around the eye, temporal gland and ear on both sides of elephant’s head are individually unique and, with application of high-resolution photographs, can also be used for individual identification. In fact, the wrinkle pattern is highly consist- ent and reliable as the primary identifiable feature; it changes little over time, facilitates identification of individuals with non-distinctive ear pattern (e.g., calves), and performs well against several practical challenges to the traditional ear-pattern approach. We used data from a 3-year photo-identification study of African elephant population to examine how the two identification methods, one that uses marks on elephant ears and the other using facial wrinkle pattern, affect the results of basic analyses of social dynamics, such as patterns of associations and social preferences, derived from datasets generated with these two identification methods. Comparative analyses demonstrate that by increasing the identifiability of otherwise poorly marked individuals and minimising identification error, the wrinkle-based method reduces substantially the sample bias, enhances the robustness of datasets, and minimises analytical error. While ear-pattern-based distinctiveness is age- dependent, the wrinkle-based method facilitates a more representative sample of the population, with photo-ID data collected non-discriminately across all age classes. This carries further implications, such as enabling more accurate depiction of elephant sociality, long-term population monitoring, calculation of class-specific population parameters, etc. Adopting the facial wrinkle pattern for elephant individual identification is relatively easy, and we encourage future and ongoing stud- ies to consider incorporating the facial wrinkle approach. Given the advantages of wrinkle-based identification and recent advances in machine learning, we recommend it to be considered for the development of automated matching algorithms; such development would benefit long-term socio-behavioural studies and monitoring of elephant populations.
... On occasion, other adult females and juveniles guard or instruct calves, reflecting the highly social and cohesive nature of elephant families . Unlike the social-group-living females, pubertal males disperse from their natal family at an average age of 14 Poole, 1989). African and Asian elephants exhibit a polygynous mating system, in which adolescent males are known to associate with other bulls, depending on their age and sexual state, and may rove between female groups throughout the year to temporarily associate and start competing with one another over receptive females (Eisenberg et al., 1971;Moss & Poole, 1983;Poole, 1989). ...
... Unlike the social-group-living females, pubertal males disperse from their natal family at an average age of 14 Poole, 1989). African and Asian elephants exhibit a polygynous mating system, in which adolescent males are known to associate with other bulls, depending on their age and sexual state, and may rove between female groups throughout the year to temporarily associate and start competing with one another over receptive females (Eisenberg et al., 1971;Moss & Poole, 1983;Poole, 1989). ...
Vocal production learning is the ability to modify a vocal output in response to auditory experience. It is essential for human speech production and language acquisition. Vocal learning evolved independently several times in vertebrates, indicating evolutionary pressure in favor of this trait. This enables cross-species comparative analysis to be used to test evolutionary hypotheses. Humans share this ability with a versatile but limited group of species: songbirds, parrots and hummingbirds, bats, cetaceans, seals, and elephants. Although case studies demonstrate that African savanna and Asian elephants are capable of heterospecific imitation, including imitation of human words, our understanding of both the underlying mechanisms and the adaptive relevance within the elephant’s natural communication system is limited. Even though comparing phylogenetically distant species is intriguing, it is also worthwhile to investigate whether and to what extent learned vocal behavior is apparent in species phylogenetically close to an established vocal learner. For elephants, this entails determining whether their living relatives share their special ability for (complex) vocal learning.
In this review, we address vocal learning in Elephantidea and Sirenia, sister groups within the Paenungulata. So far, no research has been done on vocal learning in Sirenians. Because of their aquatic lifestyle, vocalization structure, and evolutionary relationship to elephants, we believe Sirenians are a particularly interesting group to study. This review covers the most important acoustic aspects related to vocal learning in elephants, manatees, and dugongs, as well as knowledge gaps that must be filled for one to fully comprehend why vocal learning evolved (or did not) in these distinctive but phylogenetically related taxa.
... Musth is a physiological and behavioral phenomenon characterized by increased testosterone, heightened aggression or unpredictability, increased sexual behavior, and a temporary rise in dominance in both wild and captive Asian [1][2][3][4][5] and African [1,[6][7][8][9][10] elephant bulls. Bulls advertise musth status through a variety of chemicals exuded in temporal gland secretions and urine [5,[11][12][13], and secretions from the paired facial temporal glands and dribbling of urine from the penile prepuce characterize physical signs of musth [3,5,6,8,9,11,12,14,15] which are also visible. ...
... The youngest male showed increased testosterone with age in the 5 years after his first musth cycle, and then a gradual decrease. In younger males, expression of musth is shorter and more sporadic, becoming more robust with increasing age [4,6,10,11]. All older bulls showed decreased mean testosterone past 31-40 years of age, providing evidence of age-related decreases in testosterone similar to those found in male model species [64] and humans [65,66]. ...
The conservation of endangered species and sustainability of managed populations requires considerations to ensure the health and welfare of individuals. Male elephants experience a biological phenomenon called “musth”, which is characterized by increased testosterone production, temporal gland secretion and urine dribbling, heightened aggression and sexual behavior, and therefore can pose unique challenges for human safety and animal welfare. This study characterized longitudinal (9 to 22 years) patterns of circulating testosterone and cortisol in relation to musth in four adult Asian elephant bulls spanning ages from 12 to 54 years. Age-related effects on musth activity and adrenal responses to social changes and clinical health events were also examined. All bulls exhibited regular annual musth cycles. Circulating cortisol covaried positively with testosterone and musth, highlighting intrinsic patterns that should be considered when evaluating the impact of social, health, and environmental changes on adrenal glucocorticoid activity. Except for an end-of-life cortisol increase in one bull, there was no clear evidence of chronically elevated cortisol secretion outside of musth in any individual. Testosterone decreased with age in sexually mature bulls, whereas age-related changes in cortisol varied across individuals, with the three older bulls showing the greatest rate of change during musth versus inter-musth periods. In contrast to physiological factors, there was no evidence of social factors, such as addition of a new male and death of male herdmates, impacting adrenal glucocorticoid activity in these bulls in the short term. Changes in cortisol were associated with treatment for Mycobacterium tuberculosis (M. tb) in two bulls, increasing after start of treatment and decreasing with cessation of treatment, but were not clearly associated with activation of disease. This study highlights the importance of longitudinal hormone monitoring to track changes in physiological function and responses to social, health, and environmental change in elephant bulls, which is important for making more informed decisions on how to manage male elephants under varying degrees of human care to ensure welfare and safety.
... Rare bird species such as Hubara bustard are under severe pressure and extinction. The phonological effect of CC will also impact the seasons for bird migration [128]. Some mammalian species such as rodents could also be affected in terms of population dynamics and distribution. ...
... This may increase conflicts between people and large mammals such as elephants, particularly in areas where rainfall is low [129]. Subsequently, change in the intensity and duration of the rainy vs. dry seasons could change breeding rates and genetic structures in those populations [128]. ...
Climate change is happening due to natural factors and human activities. It expressively alters biodiversity, agricultural production, and food security. Mainly, narrowly adapted and endemic species are under extinction. Accordingly, concerns over species extinction are warranted as it provides food for all life forms and primary health care for more than 60–80% of humans globally. Nevertheless, the impact of climate change on biodiversity and food security has been recognized, little is explored compared to the magnitude of the problem globally. Therefore, the objectives of this review are to identify, appraise, and synthesize the link between climate change, biodiversity, and food security. Data, climatic models, emission, migration, and extinction scenarios, and outputs from previous publications were used. Due to climate change, distributions of species have shifted to higher elevations at a median rate of 11.0 m and 16.9 km per decade to higher latitudes. Accordingly, extinction rates of 1103 species under migration scenarios, provide 21–23% with unlimited migration and 38–52% with no migration. When an environmental variation occurs on a timescale shorter than the life of the plant any response could be in terms of a plastic phenotype. However, phenotypic plasticity could buffer species against the long-term effects of climate change. Furthermore, climate change affects food security particularly in communities and locations that depend on rain-fed agriculture. Crops and plants have thresholds beyond which growth and yield are compromised. Accordingly, agricultural yields in Africa alone could be decline by more than 30% in 2050. Therefore, solving food shortages through bringing extra land into agriculture and exploiting new fish stocks is a costly solution, when protecting biodiversity is given priority. Therefore, mitigating food waste, compensating food-insecure people conserving biodiversity, effective use of genetic resources, and traditional ecological knowledge could decrease further biodiversity loss, and meet food security under climate change scenarios. However, achieving food security under such scenario requires strong policies, releasing high-yielding stress resistant varieties, developing climate resilient irrigation structures, and agriculture. Therefore, degraded land restoration, land use changes, use of bio-energy, sustainable forest management, and community based biodiversity conservation are recommended to mitigate climate change impacts.
... Third, males can attempt the retention of females with many behaviours that do not have aggressive components (i.e. they are not intended to harm the female), but whose function is to try to retain her in order to mate. In mammals, retention attempts include chasing, herding, pushing, blocking, and guarding, which may or may not be accompanied by aggressive behaviour (Clutton-Brock et al. 1979, Moss 1983, Poole 1989, Cassini & Vilá 1990a, b, Rubenstein 1994, Byers 1997, Mann et al. 2000, Carling et al. 2003, Elliser & Herzing 2014, Derville et al. 2018. Finally, non-aggressive behaviour may produce harm. ...
... In Artiodactyla, chasing is the most common type of sexual disturbance. Something similar occurs in Perissodactyla Sexual aggression in mammals M. H. Cassini (Clutton-Brock et al. 1979, Rubenstein 1994, Byers 1997, Carling et al. 2003, Cetacea (Cassini & Vilá 1990b, Mann et al. 2000, Elliser & Herzing 2014, Derville et al. 2018, and elephants (Moss 1983, Poole 1989). In the present review, the only records of direct observations of male Cetacea biting females in a reproductive context, which resulted in tooth rakes on the female, occurred in a population of Indo-Pacific bottlenose dolphins (Tursiops sp.) living in Shark Bay, Western Australia (Scott et al. 2005). ...
In non‐human mammals, sexual conflict should be particularly intense because males rarely provide parental care. An expected consequence of sexual conflict is male aggression towards mates. Considering how complex measurements and interpretations of behaviours such as sexual aggression and sexual coercion are, I preferred to define operationally, as ‘sexual disturbance’, any male behaviour towards females during the pericopulatory period that can be costly for females.
The objectives in this review were as follows: 1) to estimate how widespread sexual disturbance is among mammals, 2) to analyse the types of female response to sexual disturbance, and 3) to characterise the costs of sexual disturbance to females. I conducted a systematic review by searching the literature in the Web of Knowledge database using the search tools available for 19 main journals, and I conducted a qualitative review via a taxon‐by‐taxon analysis.
Sexual disturbance was frequent in four of the 32 mammalian orders: Primates, Artiodactyla, Carnivora, and Cetacea, which all include highly polygynous taxa. The most common expression of sexual conflict around copulation is seen in behaviours associated with female retention attempts that cause minor harm. Research suggests that the most common response of females to sexual disturbance comprises female grouping around a dominant male.
... If access to unrelated females is important, the initial gradual locational dispersal of males would allow young males to achieve this , while musth might facilitate older males to encounter more unrelated females through roving behavior. In African savannah elephants (Poole 1989b) and another population of Asian elephants (Chelliah and Sukumar 2015), female elephants were observed to prefer musth males, rather than non-musth males, as mates. We cannot rule out the possibility that, while musth serves as a roving or mate searching strategy for old males, it may simultaneously provide some advantage to young males in terms of female choice if they encounter a receptive female. ...
... Male African savannah elephants have been thought to have a distinct non-musth, sexually active period (Ganswindt et al. 2005;Rasmussen et al. 2008a), during which they associate to a greater extent with female groups and have higher levels of testosterone compared with sexually inactive males. Young males also have been shown to employ alternate reproductive tactics such as sneak mating while not in musth, with some moderate success (see Poole 1989b;Hollister-Smith et al. 2007;Rasmussen et al. 2008b;Poole et al. 2011). There are no distinct locations in our study area that could result in clearly separated spaces for sexually inactive and active males, and we have not observed distinct sexually active and inactive non-musth states. ...
Musth is an annual, asynchronous, rut-like phenomenon observed in male elephants. We examined whether musth is a roving strategy, and whether musth provides a temporary advantage to young males through increased access to female groups. We collected long-term data on the musth status, associations, and locations of male elephants in the Kabini population in southern India. We sighted older males more frequently in musth than younger males. We found a greater turnover of musth than non-musth males in the study area, suggesting that musth is a roving strategy, enabling males to travel widely and away from their non-musth range. Contrary to our expectation, young (15–30 years old) males spent a smaller proportion of their musth time than their non-musth time associating with females, and associated with similarly sized female groups irrespective of musth status. Old (> 30 years old) males spent only a slightly higher proportion of their musth time than non-musth time with female groups, but associated with larger female groups during musth. Although old males in musth associated with young non-musth males more often in the presence, than in the absence, of females, young males in musth were never sighted with old non-musth males in the presence of females. Therefore, the payoff from musth, as a strategy to gain access to females, was age-specific; musth in old males allowed for increased association with females, while musth in young males restricted their access to females. There was no spatial avoidance between musth and non-musth adult males at scales larger than immediate associations. Our results suggest that musth seems to be primarily a roving strategy for old males to find and associate with females and not a strategy for young males to gain a temporary advantage over old males, within the broad age-classes that we examined.
... If access to unrelated females is important, the initial gradual locational dispersal of males would allow young males to achieve this , while musth might facilitate older males to encounter more unrelated females through roving behavior. In African savannah elephants (Poole 1989b) and another population of Asian elephants (Chelliah and Sukumar 2015), female elephants were observed to prefer musth males, rather than non-musth males, as mates. We cannot rule out the possibility that, while musth serves as a roving or mate searching strategy for old males, it may simultaneously provide some advantage to young males in terms of female choice if they encounter a receptive female. ...
... Male African savannah elephants have been thought to have a distinct non-musth, sexually active period (Ganswindt et al. 2005;Rasmussen et al. 2008a), during which they associate to a greater extent with female groups and have higher levels of testosterone compared with sexually inactive males. Young males also have been shown to employ alternate reproductive tactics such as sneak mating while not in musth, with some moderate success (see Poole 1989b;Hollister-Smith et al. 2007;Rasmussen et al. 2008b;Poole et al. 2011). There are no distinct locations in our study area that could result in clearly separated spaces for sexually inactive and active males, and we have not observed distinct sexually active and inactive non-musth states. ...
We present here, the first detailed study of adult male associations in an Asian elephant population, using six years of data collected on identified males. As expected in a large, polygynous species, adult males spent greater proportions of their time solitarily or in mixed-sex groups than in all-male groups. However, the adult male associations seen were complex, with different patterns of male associations based on their age and on the presence or absence of females. Old and young males spent more time associating with their age-peers and less time associating across age classes than expected at random in the absence of females. Young males did not spend a greater proportion of their time with old males than with young males. Young males did not initiate associations with old males to a greater extent than old males approaching young males. Moreover, male age was not correlated with centrality measures in association networks and was negatively correlated with the number of unique associates per time in the absence of females. All of these suggest that male associations in female absence are primarily a means for males to test strengths against age-peers rather than an opportunity for social learning from old males. Male associations in female presence were rarer than in female absence, and old, reproductively competitive, males avoided each other in female presence, resulting in different male association network properties. Although male associations were generally weak and not stable across years, there were some significant associations. Overall, there was a smaller proportion of time spent in all-male groups, smaller group sizes, and a limited role of older males in the association network in the Kabini Asian elephant population compared to the phylogenetically closely related African savannah elephant. These differences may be related to differences in resource distributions in the two habitats.
... Female elephants are fertile for a short window of 3 to 6 days every 3 to 9 years (Moss and Poole 1983;Poole and Moss 1989). As a result, male elephants face the challenge of locating an incredibly limited and highly mobile resource while preventing access from other males (Poole 1989;Poole and Moss 1989). Males are expected to be better competitors with increasing size. ...
The primary purpose of sex is reproduction. However, because not all mating events result in fertilization and only a small number of species provide biparental care to their young, successfully reproducing individuals can rarely be identified from behavioral observations alone. Genetic tools permit reliable identification of an individual’s parents and thus of successfully reproducing individuals, because each parent passes on half of their genetic material to their offspring. In cetaceans, genetic tools are required to identify a female’s already weaned offspring and to detect successfully reproducing males due to the absence of paternal care. To date, relatively few studies have investigated variables linked to reproductive success in this taxon, owed to the difficulty of sampling entire cetacean populations. We summarize currently known factors that are linked to successful reproduction in whales, porpoises, and dolphins, as well as in terrestrial mammals with comparable life histories that give birth to single young.
... (Chiyo et al., 2011;Srinivasaiah et al., 2019;Keerthipriya et al., 2021). From field studies, we know that the condition of musth changes inter-and intrasexual association patterns (Poole, 1989b;Keerthipriya et al., 2020). I also expected to observe more frequent aggressive behavior during my observations of musth, as has been described in other in-situ (Poole, 1987(Poole, , 1989aGanswindt et al., 2005b) and ex-situ (Jainudeen et al., 1972a;Lincoln & Ratnasooriya, 1996;Flora et al., 2003;Ganswindt et al., 2005a;LaDue et al., 2014;Duer et al., 2016) studies. ...
In-situ and ex-situ populations of Asian elephants (Elephas maximus) are unsustainable in the long-term and require integrative approaches to address issues impacting their conservation status. Male elephants pose distinct challenges: they are more likely to engage in human–elephant conflict in the wild, and they require specialized care in zoos and other similar settings. Musth is a unique sexual state in elephants and is thought to be a major contributor to these challenges. However, our limited understanding of the nature of musth in Asian elephants limits our ability to implement animal-centered conservation strategies. The purpose of this dissertation was to characterize the behavioral and physiological variation of musth in wild and zoo-housed male Asian elephants in Sri Lanka and North America, respectively. This work was organized by four principal objectives: (1) identify intrinsic and extrinsic factors that influence behavioral activity around musth in wild and zoo-housed male elephants; (2) investigate the effects of age and musth on male social behavior in wild and zoo-housed elephants, and group formation in wild elephants; (3) utilize fecal samples collected longitudinally from zoo- housed elephants to determine factors that influence musth and three fecal hormone metabolites potentially associated with musth; and (4) integrate behavioral and hormonal datasets from wild and zoo-housed elephants to explore potential associations between behavioral and hormonal variation in males. To draw qualitative comparisons, data collection procedures were similar between in-situ and ex-situ elephant populations. In the first study, I identified characteristic behaviors that changed with the progression of musth in both wild and zoo-housed elephants, including increased activity, investigatory behavior, locomotion, and stereotypy (in zoo elephants), and decreased foraging. Behavior in zoo elephants was also influenced by factors such as age, space availability, and temperature. Based on these results, I proposed four behavioral stages of musth (non- musth, early musth, full musth, and post-musth) that can be reliably monitored with visible musth indicators [i.e., temporal gland secretions (TGS) and urine dribbling (UD)]. For the second study, I used a similar observational approach to identify factors that influence social behavior in male elephants. Results of this study showed that group formation in wild male elephants was associated with the interaction of age and musth status. Furthermore, broad categories of social behavior (aggression, prosocial behavior, dominance behavior, and submissive behavior) were correlated with changes in the social environment in wild and zoo-housed elephants, and these behaviors also were associated with age and musth status in zoo elephants. In the third study involving physiological variation of musth in zoo-housed elephants, I found strong associations of intrinsic and extrinsic factors with concentrations of fecal androgen metabolites (FAM) and fecal glucocorticoid metabolites (FGM). Additionally, the duration of musth episodes was negatively associated with body condition and positively associated with exposure to male conspecifics. TGS and UD activity also was correlated with changes in FAM and FGM concentrations. Finally, the fourth study demonstrated that many of the behavioral changes characteristic of musth also were associated with increased FAM concentrations (and increased active behavior and locomotion was positively related to FGM concentration in zoo-housed elephants), illustrating the multiple scales with which male elephants respond to changing internal and external environments. This dissertation emphasized the inherent variation associated with behavioral and physiological correlates of the heightened reproductive state of musth in Asian elephants, an endangered species with in-situ and ex-situ sustainability challenges. In identifying the intrinsic and extrinsic influences of this variation, we can develop informed approaches to conserve elephants as they respond to ever-changing internal and external environments.
... This recurrent ranging pattern may result from an extended process of male-male contests, eventually leading to temporal-partitioning with other similarly-aged males such that they are not in direct competition during their musth periods. Studies of African savannah elephants indicate that older males may suppress the musth of younger males and severely limit their access to oestrus females [55][56][57][58] . The duration of musth is likewise observed to increase with age in African savannah elephants 56,59 . ...
Animals’ space requirements may vary according to life-history and social considerations. We observed 516 wild adult Asian elephants from both sexes, over 9 years, to investigate how life-history traits and social behavior influence protected-area (PA) use at Udawalawe National Park, Sri Lanka. Male PA-use, quantified in terms of average between-sightings-interval (BSI), was significantly influenced by the interaction of age class and motivational state (i.e. reproduction vs. foraging). Musth lengthened with age, with a median of 24.5 days for ages 21–30, 32.5 days for ages 31–40, and 45 days for those > 40. A minority (11%) used it exclusively during musth, while others used it exclusively for foraging (44%) or both (45%). Males using it in both states and older musth-only males were more likely to be seen across years. There were 16 social communities containing between 2–22 adult females. Females’ BSI was significantly influenced by social ties, but this relationship was weak, because members of social communities do not necessarily disperse together, resulting in high individual variation in space-use. Inter-annual variability in sightings among individuals of both sexes indicates that around ¾ of the population is likely non-residential across years, challenging the prevailing fortress-conservation paradigm of wildlife management.
... Alternatively, sexual selection can mean that older males invest more in sexual signalling [43] and have greater reproductive success than young males. This can happen in cases where older males are larger [44], hold better territories [45], or have more extensive song-repertoires [46] and thus are better at securing mates. If male reproductive success increases with age, while female reproductive success remains constant or declines; sexual selection can favour the evolution of longer lives in males than females [17]. ...
Life-history strategies are diverse. While understanding this diversity is a fundamental aim of evolutionary biology and biodemography, life-history data for some traits-in particular, age-dependent reproductive investment-are biased towards females. While other authors have highlighted this sex skew, the general scale of this bias has not been quantified and its impact on our understanding of evolutionary ecology has not been discussed. This review summarizes why the sexes can evolve different life-history strategies. The scale of the sex skew is then discussed and its magnitude compared between taxonomic groups, laboratory and field studies, and through time. We discuss the consequences of this sex skew for evolutionary and ecological research. In particular, this sex bias means that we cannot test some core evolutionary theory. Additionally, this skew could obscure or drive trends in data and hinder our ability to develop effective conservation strategies. We finally highlight some ways through which this skew could be addressed to help us better understand broad patterns in life-history strategies.
... Saidimu's ability to adapt to a new environment may be attributed to his relatively young age (20 years old). By the time male elephants reach their early twenties, they have dispersed from their natal herd and are in a highly transitional stage in their life, of changing sexual rank, state, behaviour and associations (Poole, 1989a(Poole, , 1989b(Poole, , 1996. Thus, they have greater behavioural flexibility and adaptability, and consequently have better survival rates (Evans, 2006). ...
Translocation of elephants is used to mitigate human‐elephant conflict in Asia and Africa. However, few studies investigate how translocations affect the movements and social behaviour of individuals following their release, which may have important implications for whether translocated animals survive and succeed. Using GPS‐tracking data, we explored movements of five translocated bull elephants ( Loxodonta africana ) moved to Tsavo, Kenya, and compared them with five resident bull elephants. Position data was collected hourly for 1 year (March 2018–March 2019), and analysed to investigate home range, displacement rates, problematic behaviour and group size. Of the five translocated elephants, three were illegally killed and one continued to break fences and raid crops. Only one elephant stayed away from human settlement. We found group size and composition to be significantly different, with translocated elephants observed in smaller groups with no female elephant interactions. All elephants showed variation in home ranges and displacement rates, but differences were not significant between resident and translocated elephant groups. For future translocations, we recommend careful consideration of elephant social systems, elephant age, timing, release site and proximity to human settlements that might create human‐elephant conflict. This will improve chance for success of such high‐stake and expensive translocations.
... Musth presumably evolved to facilitate inter-and intrasexual interactions (LaDue et al., 2022); once thought to be largely solitary upon reaching sexual maturity, male Asian elephants are now known to have complex social lives into adulthood (Chiyo et al., 2011;Srinivasaiah et al., 2019;Keerthipriya et al., 2021). From field studies, we know that the condition of musth changes inter-and intrasexual association patterns (Poole, 1989b;Keerthipriya et al., 2020). We also expected to observe more frequent aggressive behavior during our observations of musth, as has been described in other in-situ (Poole, 1987(Poole, , 1989aGanswindt et al., 2005b) and ex-situ (Jainudeen et al., 1972a;Lincoln and Ratnasooriya, 1996;Flora et al., 2003;Ganswindt et al., 2005a;LaDue et al., 2014;Duer et al., 2016) studies. ...
Complementary studies of wild and zoo-housed animals offer insight into behavioral variation across a range of conditions including the context under which various behaviors evolved in natural settings. This information can be used to improve the sustainability of in-situ and ex-situ populations and enhance the well-being of individuals. Managed ex-situ populations are critical to the long-term existence of Asian elephants, yet relatively little is known about male reproductive behavior compared to females. Male elephants undergo a unique sexual state called “musth” that further complicates in-situ and ex-situ management strategies. The ability to manage musth males to enhance breeding success and overall wellness of elephants is dependent upon better understanding how intrinsic and extrinsic factors influence male behavioral variation around musth. Here, we observed 62 free-ranging male Asian elephants in Sri Lanka and compared their behavior to observations from 26 elephants managed in facilities around the US. We hypothesized that musth is associated with significant behavioral changes that can be used to define distinct stages in the progression of musth. During observations, we quantified environmental variables and recorded musth status of each focal elephant using visual indicators (temporal gland secretions and urine dribbling). We showed that musth’s behavioral correlates (including changes in locomotion, foraging, alertness, and chemosensory behavior) were remarkably similar in wild and zoo-housed elephants. We also found that behavioral variation around musth was also associated with intrinsic (e.g., musth stage, age) and extrinsic factors (e.g., space availability, temperature) in zoo-housed, but not wild, elephants, indicating that musth is potentially plastic in changing environments. As musth progressed, we noted distinct behavioral signatures that define four stages of sexual activity in male elephants: non-musth, early musth, full musth, and post-musth. Finally, although we did not observe significant changes in overall social behavior (including aggression) during musth, we found that elephants increased the frequency with which they displayed certain behaviors associated with communication (e.g., alertness, chemosensory behavior, ear-flapping) in both populations. Together, these results indicate the significant behavioral changes that occur during musth in wild and zoo-housed elephants, and that musth progresses in distinct behavioral stages that can be easily distinguished by visual indicators. Studies like these serve to provide wildlife managers with information about a species’ unique, evolved behavioral strategies and how these seemingly fixed behaviors may be influenced by intrinsic and extrinsic factors in predictable ways.
... Reproductive coordination can be achieved between ovulating females and unrelated males using vocalizations over short and long distances [68,99]. Female African savanna elephants in mid-estrus use loud, low frequency calls to attract multiple males to their location, who then may compete for breeding access [42,100]. Male African savanna elephants use similar 'musth rumbles,' which are low-frequency calls that advertise sexual state [42,101,102]. ...
Elephants are well known for their socio-cognitive abilities and capacity for multi-modal sensory perception and communication. Their highly developed olfactory and acoustic senses provide them with a unique non-visual perspective of their physical and social worlds. The use of these complex sensory signals is important not only for communication between conspecifics, but also for decisions about foraging and navigation. These decisions have grown increasingly risky given the exponential increase in unpredictable anthropogenic change in elephants’ natural habitats. Risk taking often develops from the overlap of human and elephant habitat in Asian and African range countries, where elephants forage for food in human habitat and crop fields, leading to conflict over high-quality resources. To mitigate this conflict, a better understanding of the elephants’ sensory world and its impact on their decision-making process should be considered seriously in the development of long-term strategies for promoting coexistence between humans and elephants. In this review, we explore the elephants’ sensory systems for audition and olfaction, their multi-modal capacities for communication, and the anthropogenic changes that are affecting their behavior, as well as the need for greater consideration of elephant behavior in elephant conservation efforts.
... Male elephants foraged significantly less when they were with females compared to when they were alone or with other males ( Figure 5). Elephants usually form same-sex groups [29]; when adult male elephants are associated with females, it is usually only for short periods of time, and for reproductive purposes when females are close to or in oestrus [28,72]. As a result, mixed-sex groups with receptive females are accompanied by more males compared to groups with females which are not in oestrus [73]. ...
African savannah elephants (Loxodonta africana) are well-known as ecosystem engineers with the ability to modify vegetation structure. The present study aimed to examine how male elephant foraging behaviour is affected across (a) season (wet versus dry); (b) time of day (before or after noon); (c) presence or absence of other elephants; and (d) reproductive state (musth versus no musth). Six radio-collared adult elephant bulls were observed twice per week from June 2007–June 2008 in Kruger National Park (KNP), South Africa. Using generalized linear mixed effect modeling, results indicate that elephant bulls graze more during the wet season and browse more during the dry season. To potentially offset the costs associated with thermoregulation during the heat of the day, KNP elephants spent more time foraging during the morning, and more time resting during the afternoon. Male elephants also foraged significantly less when they were associated with females compared to when they were alone or with other males. This is likely due to male–female associations formed mainly for reproductive purposes, thus impeding on male foraging behaviours. In contrast, the condition of musth, defined by the presence of related physical signs, had no significant effect on foraging behaviour.
... In another Asian elephant population, 15-20-year-old non-musth males engaged in sneak matings and 20-30-year-old non-musth males engaged in consortships more than expected by chance (Chelliah and Sukumar, 2013). As there is evidence for females preferring old musth males over young non-musth males in both African savannah (Poole, 1989) and Asian elephants (Chelliah and Sukumar, 2013), it would be interesting to find out how much mating and reproductive success is acquired by young non-musth males in this population. In the Samburu population of African savannah elephants, young males spent most of their sexually active state out of musth. ...
We present a detailed study of male associations in the Asian elephant, using 6 years of data on identified, non-musth males. Adult males spent greater proportions of their time solitarily than in mixed-sex or in all-male groups. Old (over 30 years) males were sighted more frequently with their age-peers and less frequently with young (15–30 years) males than expected at random in all-male groups. Young males were not sighted more frequently with old males than with young males, and did not disproportionately initiate associations with old males. These results suggest that male associations, in the absence of females, may allow for old non-musth males to test strengths against age-peers. Social learning from older individuals did not seem to be important in male associations, unlike that observed in the African savannah elephant. We also found a constraint on the sizes of all-male groups, similar to that seen in female groups in our study population, and all-male groups were rarer and smaller than those in African savannah elephant. Although male associations were weak, most males had a significant top associate, with whom their association was the strongest, in female absence. In mixed-sex groups, male associations occurred at random, suggesting that males were tracking female groups independently. Differences in male social organization from that of the related African savannah elephant that occupies a similar niche possibly arise from differences in ecology.
... Females of both species may exercise some mate choice and have been found to respond more positively to mating attempts by large/musth males 23, 120 . In the Amboseli African savannah elephant population, old/musth males showed more mate guarding and obtained a higher number of matings than young/nonmusth males 120 . Subsequent paternity analyses also showed that age and musth affected paternity success, with older males amongst those in musth usually being more successful in siring offspring 63 . ...
We review studies of the social systems of the living elephants—the Asian elephant (Elephas maximus), African savannah elephant (Loxodonta africana), and African forest elephant (Loxodonta cyclotis). Social systems include social organisation, the way relationships are structured, and the mating system; we describe each of these in turn, drawing from long-term observational studies and studies based on indirect methods in more inaccessible populations. Male and female elephants exhibit different adult lifestyles: females live in fission–fusion societies, whereas males disperse from their natal groups and subsequently associate with other males and females only temporarily. Associations and dominance relationships among females and among males may be complex and structured by factors such as genetic relatedness and relative ages. Elephants are polygynous and males compete amongst themselves for access to females. The outcome of such competition may be shaped by musth (a rut-like phenomenon) and age. Molecular markers have been used to understand aspects of social structure and mating system in some populations; we point to these studies and discuss further avenues of research. We also comment on how anthropogenic activities affect social systems, and the relevance of studying social systems in the context of conservation.
... Hypothesis 1: Prevention of Infanticide -females shouldencourage calling only when there are infants present, and hence presumably, not in the breeding season.Hypothesis 2: Hale Quality -females should encourage calling during the breeding season, or when there is least opportunity for infanticide to occur.Unfortunately, there are no data available from the present study to test whether females are inciting male-male competition as a means of selecting new mating partners (Hypothesis 2), as reported for several mammals (elephants -Poole, 1989? elephant seals-Cox & LeBoeuf, 1977? ...
In the past, studies of territoriality in primates have concentrated on the role of males in territorial defence. But sociobiological theory of female strategies, and in particular Wrangham's model of female-bonded primate groups, suggest that in many species females should be investing considerable amounts of energy in defence of their food resources against other groups of females. The aims of this thesis are to: 1. investigate the roles of male and female Cercopithecus diana in territorial defence, and 2. determine whether female behaviour is consistent with food resource defence and male behaviour with reproductive resource defence as predicted by Wrangham's model. Annual activity budgets, feeding, ranging and territorial calling behaviour of two groups of C. diana are presented, alongside information on plant production cycles and the spatial distribution of potential food resources. Diana monkeys were observed living in groups of about 20 animals, comprising 1-2 adult males, 6-10 adult females, and subadults, juveniles and infants. Infants were born during the dry season. Diana monkeys feed on fruits, flowers, leaves and arthropods. Diet varies across the seasons following plant production cycles. Ranging patterns are determined, at least in part, by the spatial distribution of particular flowers and fruits that are important components of the diet. Females initiate territorial calling bouts significantly more often than does the group male. Intergroup encounters occurred very infrequently, but when they did it was the females, subadults and juveniles that were observed fighting with other groups while the males gave loud calls and jumping displays to one another. The thesis looks at whether females are defending food resources against other females. Territorial calling is investigated with respect to location within territory, and spatial distribution of important food resources. Male calling behaviour and defence of reproductive females is also considered. The implications of Diana monkeys calling behaviour are discussed in relation to theories of primate territoriality and defence with particular reference to Wrangham's model of female-bonded groups.
... However, all of these address only the symptoms of HEC and not the systemic issues associated with this complex problem (Mumby and Plotnik 2018). Instead, others have suggested animal-based approaches that integrate information about how known individual differences among elephants, including health (Evans and Harris 2012;Lynsdale et al. 2017), reproduction (Freeman et al. 2009;Crawley et al. 2017), behaviour (Poole 1989;Poole and Moss 1989;Freeman et al. 2010;McComb et al. 2011), cognition (Bates et al. 2008;Foerder et al. 2011;Plotnik et al. 2011) and personality (Lee and Moss 2012;Yasui et al. 2013;Seltmann et al. 2019), affect the propensity of these animals to engage in HEC. ...
ContextHuman–elephant conflict (HEC) is a major threat to Asian elephants as humans and elephants are forced to share common resources. In Sri Lanka, human-dominated landscapes adjacent to protected areas promote high rates of HEC, especially in the form of crop-foraging by elephants. Crop-foraging can be dangerous to both elephants and humans involved in the conflict. Gunfire is a common way for human communities to deter crop-foraging elephants, and gunshot wounds are commonly described in this elephant population on necropsy. AimsWe sought to quantify and describe unique scar patterns among Asian elephants in a protected area, Wasgamuwa National Park, attributed to HEC. Methods
We identified 38 adult female and 64 adult male elephants and recorded the age class and body condition of each with established standards. Using photographs, we counted the number, position, and relative size of all scars on each animal. Key resultsMale elephants had significantly more scars than did females, and for males, the number of scars increased progressively with age. Additionally, male elephants with higher body conditions had more scars. Finally, males tended to have more scars towards the head, especially at older ages. Conclusions
Differences in total scar counts between the sexes in this population imply that male elephants in this area more frequently engage in HEC than do females, following observations previously described in the literature. Furthermore, the fact that male elephants acquired progressively more scars as they aged, and that fatter elephants had more scars, indicates that previous exposure to HEC may not have been a deterrent for future events among these males, and potentially, crops served as valuable food sources for these animals. Finally, the changing body locations of these scars with age in males possibly shows plastic behavioural responses during crop-foraging or lower tolerance by farmers towards habitual crop foragers. ImplicationsThese results emphasise the need for animal-based approaches to HEC mitigation. Similarly, conservation managers in Sri Lanka and other elephant range countries should investigate similar methods that estimate patterns of HEC to develop effective management strategies directly targeting animals most likely to engage in conflict.
... [Thought question: Do you believe the last line of the abstract?] Poole [1989] Mate guarding, reproductive success and female choice in African elephants. Animal Behavior 37:842-49. ...
... Swelling of the perineal skin in multiple species of primates around the fertile phase of the cycle is hypothesized to have evolved because it stimulates competition among males (Nunn 1999). Acoustic signals of fertility work in the same manner and have been documented in the estrus calls of a number of different mammalian species and groups, such as African elephants, Old World monkeys, and bovids (Gouzoules et al. 1998;Poole 1989;Pradhan et al. 2006;Yeon et al. 2006). Delivering a call during times of peak fertility advertises the female's sexual receptivity and encourages dominant males to supplant subordinate males and engage in mating and subsequent mate guarding. ...
... Bulls in musth will begin seeking females in estrous, while secreting chemical signals through urinary dribbling and temporal gland secretions (Ganswindt et al. 2005). However, Poole (1989b) observed males not in musth were capable of seeking a mate and successfully breeding, ...
African elephants (Loxodonta africana) are becoming increasingly endangered due to illegal poaching and ivory trade markets. Preservation of the species is imperative to maintain fully functioning ecosystems, for future studies of social behaviour, and to allow future generations to revel in their magnificence. Conservation/game reserves, sanctuaries and zoos are attempting to make suitable captive environments that would aid successful reproduction while re-establishing wild African elephant populations. Unfortunately, there has been very little success with breeding in captivity. The objective of this review is to evaluate sexual behaviours in wild and captive populations to distinguish what features and reproductive techniques should be implements in captive environments to potentially achieve an effective and successful breeding program. The results of this review are that captive environments are limiting in many factors that impede natural behaviours that may lead to copulation and successful reproduction: group sizes and composition, age and sex of groups, and endocrinological changes due to stress. Natural environments are difficult to mimic which has led to development of reproductive technologies which may improve reproductive success. There have been some advancements in spermatozoa extension and preparation for cryopreservation and use in artificial insemination. Extenders with increased cholesterol from egg yolk have proven beneficial in maintaining sperm viability through transport and storage providing a promising outlook into the future of population restoration projects in captive environments. ii ACKNOWLEDGEMENTS
... Studies of birds (Wetton et al. 1995;Mountjoy and Lemon 1996;Sundberg and Dixon 1996;Wagner et al. 1996;Richardson and Burke 1999;O'Loghlen and Rothstein 2003), lizards (Lopez et al. 2003), insects (Somashekar and Krishna 2011), mammals (Poole 1989;Ferkin 1999;Komers et al. 1999), and fish (Côté and Hunte 1993) have shown a female preference for older males, as evidenced by higher reproductive success of older males (reviewed in the work of Brooks and Kemp 2001), and this relatively high reproductive success has occasionally been associated with relatively more intense advertisement signals (Mountjoy and Lemon 1996;Sundberg and Dixon 1996;O'Loghlen and Rothstein 2003). Some studies have also demonstrated the ability of females to use assessment signals to distinguish between adult and subadult individuals (Lopez et al. 2003;O'Loghlen and Rothstein 2003), and a cross-sectional study of captive voles has shown that females prefer the scents of older individuals (Ferkin 1999). ...
Age-related changes in assessment signals occur in a diverse array of animals, including humans. Age-related decline in vocal quality in humans is known to affect perceived attractiveness by potential mates and voters, but whether such changes have functional implications for nonhuman animals is poorly understood. Most studies of age-related change in animal signals focus on increases in signal quality that occur soon after the age of first breeding ("delayed maturation"), but a few have shown that signal quality declines in older individuals after a mid-life peak ("behavioral senescence"). Whether other individuals are able to detect this senescent decline of assessment signals has not previously been tested. Here we use playback experiments to show that wild male swamp sparrows (Melospiza georgiana) respond more aggressively to songs from 2-year-old males as compared with songs from the same males when they are 10 years old. Senescence in signals that, like birdsong, affect reproductive success through intrasexual competition or mate choice may be of evolutionary significance.
... These 'mating calls' are a sexually selected trait, primarily used by males to attract female mates (reviewed in Fedorka & Mousseau, 2001) and advertise the male mating success (e.g., mice - White et al., 1998). Females use copulation calls to incite mate guarding behaviour in the male mates (e.g., African elephants - Poole et al., 1988;Poole, 1989) and to prevent or end unwanted copulations by attracting another high-ranking male (e.g., fowls -Pizzari, 2001;Løvlie et al., 2014). ...
Copulation calls are mating-associated vocalizations that are common in primates, with females vocalizing after copulation in several Old World monkeys and apes. Baboon females typically produce copulation calls that correlate with fertile phase. Calls are, thus, regarded as an upshot of cycle physiology and sexually selected calls. Here, we describe three captive troops of olive baboons wherein, against expectation, females suppressed vocalizing during copulations. Vaginal cytology, together with sexual swelling observations, confirmed that females experienced full receptive cycles. Ovulation did not affect vocal probability during sex, while copulation calls were predicted by male ejaculation just as in other Old World primate species. Results cast doubt on the existence of physiological triggers for baboon copulation calls. Social factors may instead play a larger role. Alterations in social structure (as typically observed in the wild) may be implemented strategically as captive enrichment in order to reveal how females in highly social primates change sexual strategies and, therefore, the use of their copulation calls.
... During fasting and low food availability, protein turnover is reduced and concentrations of T3 are low (St Aubin et al., 1996;Oritz et al., 2010). Elephant bulls in musth reduce their food intake and lose body condition (Poole 1987(Poole , 1989, and musth has been linked to reduced thyroid hormone concentrations (Chave et al., 2019). As shown for the EIA validation for the research presented here, low body condition scores were associated with low concentrations of mT3 in elephant bulls. ...
Conservation biologists can use hormone measurements to assess animals' welfare, reproductive state, susceptibility to stressors, as well as energy expenditure. Quantifying hormone concentrations from faecal samples is particularly advantageous as samples can be collected without disturbing animals' behaviour. In order for an endocrine marker to be useful for wildlife managers, we need to understand how extrinsic and intrinsic factors affect hormone concentrations in free-ranging animal populations. Thyroid hormones are linked to basal metabolic rate and energy expenditure. Previous research demonstrated that triiodothyronine (T3) can be measured successfully in faecal matter of African elephants, Loxodonta africana. However, to our knowledge, research into factors affecting changes in elephant T3 levels has only been carried out in captive elephants so far. Thus, we present the first study of faecal T3 metabolite (mT3) concentrations of a large population of free-ranging African elephants. Over 15 months, we collected faecal samples from identified (n = 43 samples) and unidentified (n = 145 samples) individuals in Madikwe Game Reserve, South Africa. We investigated whether vegetative productivity [normalized difference vegetation index (NDVI)] in interaction with mean monthly temperature, age and sex affected mT3 concentrations. We found a significant negative interaction effect of NDVI and temperature. Increasing NDVI was related to higher concentrations of mT3, but increasing temperature was related to a decrease in mT3 concentrations in individually identified and unidentified elephants. In unidentified individuals, juvenile elephants had significantly higher mT3 concentrations compared to adult elephants. Faecal T3 can successfully be quantified in samples from free-ranging elephant populations and thus provides insight into energy expenditure in large herbivores.
... Musth is similar to rutting behaviour in ungulates and is associated with periodic increases of testosterone secretion. Most matings occur in this period (Poole, 1989). During musth, the animal becomes more restless, energetic, aggressive and generally irritable and oversensitive to sound and movements. ...
Successful management of a violent male Asian elephant (Elephas maximus) in musth was carried out using 700 mg Xylazine HCl to obtain desired standing anaesthesia. The legs of elephant were tied with chains and tethered by using special jute rope to prevent his movement until the musth period was over. In brief, better awareness of people on physiological behavoiur of elephants for detection of musth as well as to adopt appropriate
management procedures is referred
... Our framework can therefore investigate species that show intraspecific variation in their social systems (Schradin, Hayes, Pillay, & Bertelsmeier, 2018). Examples include those where males and females live separately outside of the breeding season, as in elephants and many ungulate species (Coulson, Albon, Guinness, Pemberton, & Clutton-Brock, 1997;Poole, 1989), or where sexes are organized in different ways, as in lions where one or multiple males' territory might encompass several cohesive female prides F I G U R E 1 Scheme of framework. The eight dimensions can be broadly classed into three categories (organizational, composition, and temporal). ...
Mammalian societies represent many different types of social systems. While some aspects of social systems have been extensively studied, there is little consensus on how to conceptualize social organization across species. Here, we present a framework describing eight dimensions of social organization to capture its diversity across mammalian societies. The framework uses simple information that is clearly separated from the three other aspects of social systems: social structure, care system, and mating system. By applying our framework across 208 species of all mammalian taxa, we find a rich multidimensional landscape of social organization. Correlation analysis reveals that the dimensions have relatively high independence, suggesting that social systems are able to evolve different aspects of social behavior without being tied to particular traits. Applying a clustering algorithm allows us to identify the relative importance of key dimensions on patterns of social organization. Finally, mapping mating system onto these clusters shows that social organization represents a distinct aspect of social systems. In the future, this framework will aid reporting on important aspects of natural history in species and facilitate comparative analyses, which ultimately will provide the ability to generate new insights into the primary drivers of social patterns and evolution of sociality. Social organization is an aspect of animal social systems that has not been conceptualized yet and is often reduced to group size. This framework describes eight central dimensions of social organization to capture its diversity across mammalian societies. By applying our framework across 208 species of all mammalian taxa, we find a rich multidimensional landscape of social organization.
... The observed blue whale behavior, in all three cases, likely represented a competitive behavior linked to reproduction, as described by Sears and Perrin (2002). Escorting behavior (a male accompanying a female) is known to occur in many animal taxa, e.g., humpback whales (Megaptera novaeangliae) and African elephants (Loxodonta africana), as well as in various bird and primate species; Alberts, Altmann, & Wilson, 1996;Baker & Herman, 1984;Birkhead, 1979;Birkhead, Johnson, & Nettleship 1985;Clapham, Palsbøll, Mattila, & Vasquez, 1992;Poole, 1989;Tyack & Whitehead, 1982). Escorting allows a male to defend a female, limiting access of other males to the female and thereby increasing the likelihood of siring potential offspring. ...
... One argument has been that male-male competition may be in part responsible (Roca et al. , 2007. Reproductive success among savanna elephant males is known to depend on body size and age, mediated by periods of musth in which testosterone increases and males become more aggressive towards other males (Poole 1989;Slotow et al. 2000;Hollister-Smith et al. 2007;Rasmussen et al. 2008). Fullygrown forest elephant males are only half as massive as fully-grown savanna elephant males (Groves et al. 1993;Groves and Grubb 2000a, b). ...
During the last two decades, our understanding of the genetics of African elephant populations has greatly increased. Strong evidence, both morphological and genetic, supports recognition of two African elephant species: the savanna elephant (Loxodonta africana) and the forest elephant (L. cyclotis). Among elephantids, phylogeographic patterns for mitochondrial DNA are highly incongruent with those detected using nuclear DNA markers, and this incongruence is almost certainly due to strongly male-biased geneflow in elephants. As our understanding of elephant population genetics has grown, a number of observations may be considered enigmatic or anomalous. Here, several of these are discussed. (i) There are a number of within-species morphological differences purported to exist among elephants in different geographic regions, which would be difficult to reconcile with the low genetic differentiation among populations. (ii) Forest elephants have a higher effective population size than savanna elephants, with nuclear genetic markers much more diverse in the forest elephants than savanna elephants, yet this finding would need to be reconciled with the life history of the two species. (iii) The savanna and forest elephants hybridize and produce fertile offspring, yet full genome analysis of individuals distant from the hybrid zone suggests that gene flow has been effectively sterilized for atleast ∼500,000 years. (iv) There are unexplored potential ramifications of the unusual mito-nuclear patterns among elephants. These questions are considered in light of highmale and low female dispersal in elephants, higher variance of reproductive success among males than females, and of habitat changes driven by glacial cycles and human activity.
... An important physiological change that occurs in male elephants during this phase is the onset of musth 17,18 , characterized by enhanced testosterone level and increased sexual activity 13,19 . When in musth, male African and Asian elephants are known to associate with females to mate with them 13,20,21 . Dynamic changes in social associations and behavioural strategies seem to be appearing amongst both female and male elephants, in populations that are living in rapidly changing ecological and anthropogenic environments [21][22][23] . ...
Male Asian elephants are known to adopt a high-risk high-gain foraging strategy by venturing into agricultural areas and feeding on nutritious crops in order to improve their reproductive fitness. We hypothesised that the high risks to survival posed by increasingly urbanising and often unpredictable production landscapes may necessitate the emergence of behavioural strategies that allow male elephants to persist in such landscapes. Using 1445 photographic records of 248 uniquely identified male Asian elephants over a 23-month period, we show that male Asian elephants display striking emergent behaviour, particularly the formation of stable, long-term all-male groups, typically in non-forested or human-modified and highly fragmented areas. They remained solitary or associated in mixed-sex groups, however, within forested habitats. These novel, large all-male associations, may constitute a unique life history strategy for male elephants in the high-risk but resource-rich production landscapes of southern India. This may be especially true for the adolescent males, which seemed to effectively improve their body condition by increasingly exploiting anthropogenic resources when in all-male groups. This observation further supports our hypothesis that such emergent behaviours are likely to constitute an adaptive strategy for male Asian elephants that may be forced to increasingly confront anthropogenically intrusive environments.
... Musth duration and regularity is positively related to age, with males over 35 displaying regular musth periods once a year for an extended duration (~2 months), whilst younger bulls between ~26 and 35 tend to express musth characteristics for up to 2 weeks several times a year (Poole, 1987;Poole, Lee, Njiraini, & Moss, 2011). Thus, the reproductive success of a male elephant increases with age, both through reductions in intrasexual competition by the escalation of size-related dominance (Poole, 1989a), and an increase in intersexual selection by females for older males (Moss, 1983;Poole, 1989b). However, despite the reproductive dominance of older males, younger males still contribute to the gene pool (Hollister-Smith et al., 2007;Rasmussen, Okello, et al., 2008). ...
Long‐term bio‐logging has the potential to reveal how movements, and hence life‐history trade‐offs, vary over a lifetime. Reproductive tactics in particular may vary as individuals' trade‐off current investment versus lifetime fitness. Male African savanna elephants (Loxodona africana) provide a telling example of balancing body growth with reproductive fitness due to the combination of indeterminate growth and strongly delineated periods of sexual activity (musth), which results in reproductive tactics that alter with age.
Our study aims to quantify the extent to which male elephants alter their movement patterns, and hence energetic allocation, in relation to (a) reproductive state and (b) age, and (c) to determine whether musth periods can be detected directly from GPS tracking data.
We used a combination of GPS tracking data and visual observations of 25 male elephants ranging in age from 20 to 52 years to examine the influence of reproductive state and age on movement. We then used a three‐state hidden Markov model (HMM) to detect musth behaviour in a subset of sequential tracking data.
Our results demonstrate that male elephants increased their daily mean speed and range size with age and in musth. Furthermore, non‐musth speed decreased with age, presumably reflecting a shift towards energy acquisition during non‐musth. Thus, despite similar speeds and marginally larger ranges between reproductive states at age 20, by age 50, males were travelling 2.0 times faster in a 3.5 times larger area in musth relative to non‐musth. The distinctiveness of musth periods over age 35 meant the three‐state HMM could automatically detect musth movement with high sensitivity and specificity, but could not for the younger age class.
We show that male elephants increased their energetic allocation into reproduction with age as the probability of reproductive success increases. Given that older male elephants tend to be both the target of legal trophy hunting and illegal poaching, man‐made interference could drive fundamental changes in elephant reproductive tactics. Bio‐logging, as our study reveals, has the potential both to quantify mature elephant reproductive tactics remotely and to be used to institute proactive management strategies around the reproductive behaviour of this charismatic keystone species.
... Musth is similar to rutting behaviour in ungulates and is associated with periodic increases of testosterone secretion. Most matings occur in this period (Poole, 1989). During musth, the animal becomes more restless, energetic, aggressive and generally irritable and oversensitive to sound and movements. ...
... Higher Aggressiveness in male elephants might be explained by their need to assess each other's dominance status by less-aggressive sparring bouts or by more-aggressive interactions during musth 14 . The Aggressiveness personality trait is related to ratings of aggressive, moody, and dominant behaviour 11 (Fig. 1), and higher aggression has a crucial impact in maximising reproductive success in male elephants as older larger and more aggressive males are more successful in mate guarding than less aggressive males 33 . ...
Personality, i.e. consistent between-individual differences in behaviour, has been documented in many species. Yet little is known about how males and females of long-lived, highly social species differ in their measures of personality structure. We investigated sex differences in the mean, variance, and covariance of three previously reported personality traits (Attentiveness, Sociability, Aggressiveness) in 150 female and 107 male Asian elephants (Elephas maximus) from a semi-captive population in Myanmar. These three personality traits were obtained by performing exploratory factor analysis on 28 behavioural items that had been rated by experienced elephant handlers. We found that males scored significantly higher on Aggressiveness and tended to score lower on Sociability than females. However, no sex difference was found in the mean scores of Attentiveness. Variances for the three personality traits did not differ between the sexes, suggesting that male and female elephants share the same range of personality variation. Likewise, trait covariances were similar between the sexes. While both sexes show complex sociality in the wild, female Asian elephants typically live in highly social family units, whereas male elephants’ social bonds are weaker. Males usually form dominance ranks by aggressive interactions, especially during musth. Our results on a large sample of individuals living in their natural environment are thus in agreement with elephant life-histories and parallel the findings of sex differences in other long-lived highly social species with similar life-histories.
... Sperm competition is a form of male-male competition, but since the sperm of two or more males compete to fertilize the ova, it can also have direct implications in intrasexual interactions (Parker, 1970). Males have evolved an array of strategies to establish final precedence of their sperm by enforcing female monogamy (Gillies 1956, Gilbert 1976, Ehrlich and Ehrlich 1978, Sillén-Tullberg 1981, Thornhill and Alcock 1983, Svard and Wiklund 1988, Dickinson and Rutowski 1989, Poole 1989, Mclain 1989, Matsumoto and Suzuki 1995, Orr 1995, Orr 1999, Sauter et al. 2001, Dixson and Anderson 2002, Schulz et al. 2008, Timmermeyer et al. 2010, Uhl et al. 2010, Carvalho et al. 2017, Malouines 2017, and any male that prevents a female from remating will be in direct conflict with her if the female would otherwise benefit from remating. This intersexual conflict can trigger sexually antagonistic coevolution (Rice 1996), where adaptations evolve in one sex in order to increase its fitness, which will result in lower fitness for the opposite sex. ...
Sexual reproduction is often associated with intra- and intersexual conflict, especially in species where females mate multiple times. A strategy that has evolved in males to ensure offspring paternity is the ability to produce a complex, external mating plug called a sphragis. The sphragis has been found in 273 butterfly species; however, little is known about the sphragides of the butterflies in the nymphalid genus Pteronymia. In this study, we describe the sphragides of all sphragis-bearing species in Pteronymia, including the newly discovered sphragides of P. alissa (Hewitson), P. andreas (Weeks), P. ozia (Hewitson), and P. zerlina (Hewitson). Three additional species, P. fulvimargo Butler & Druce, P. oneida (Hewitson), and P. ticida (Hewitson), are found to bear an irregular sphragis-like structure. We use molecular and morphological data from a recent study to construct a phylogeny of species in the genus and examine the number of independent origins of the sphragis. Our ancestral state reconstruction using Bayesian inference suggests that the sphragis evolved three times in Pteronymia, whereas parsimony character optimization performed on a maximum likelihood tree suggests only one origin of this structure. Our data on ancestral state patterns, frequency of incomplete sphragides, and morphology of female external genitalia suggest that sphragis-bearing Pteronymia may be in active intersexual conflict, where females develop strategies to prevent male plugging.
... Since the rainfall pattern for RCP 2. In terms of breeding and genetics a change in the intensity or duration of the rainy versus drought seasons could change relative breeding rates and, hence, genetic structures in these populations [79] [84]. Therefore increased rains in the OND season will have a positive impact on the elephant population of Amboseli ecosystem but work on elephant population dynamics is needed (refer to [49] [88] As indicated in this study that it is projected there is likely possibilities of increase in elephant population based on all the three RCPs 2.6, 4.5 and 8.5 in the Amboseli ecosystem which could boost tourism activities in the area. ...
Within savanna environments, movements of elephant are influenced by changes in climate especially seasonal rainfall. In this study, we investigated the possible changes in elephant population based on projected rainfall changes using regional climate models (RCM) and Representative Concentration Pathways (RCPs). The relationship between elephant and rainfall was modelled against annual, wet season, dry season rainfall based on various time lags. Future relation between elephant and rainfall was projected based on three RCPs; 2.6, 4.5 and 8.5. There was a strong linear relationship between elephant and October-November-December (OND) rains with time lag of 13 years (Y = −4016.43 + 19.11x, r2 = 0.459, P = 0.006). The rainfall trends for RCP 2.6 and 4.5 showed a slight increase in annual rainfall for the period 2006-2100 but driven by OND increases. Rainfall increase for RCP 8.5 was significant and was driven by increase in both March-April-May (MAM) and OND. These rainfall dynamics had influence on the projected elephant population in the Amboseli ecosystem. For RCP 2.6 and 4.5 the elephant population increase was 2455 and 2814 respectively. RCP 8.5 elephant population doubled to an average of 3348 elephants. In all the RCPs there are seasonal and yearly variations and absolute number varies from the average. The range of variation is small in RCPs 2.6 and 4.5 compared to RCP 8.5. Evidently, elephant population will increase based on projected rainfall projections surpassing park capacity. It therefore, requires that the Park authority put in place measures that could contain these numbers including opening of blocked wildlife corridors, maintain the cross border movement of Amboseli elephant with Tanzania in that case ensure there is no poaching. Lastly, work with local communities so that they can benefit from tourism through setting up conservancies through which they could minimize the human elephant conflicts based on the projected elephant population.
Keywords
Representative Concentration Pathways 2.6, 4.5 and 8.5, Rainfall Variability, Population Dynamics
How the underlying forces of sexual selection impact reproductive tactics including elaborate acoustic displays in cetaceans remains poorly understood. Here, I combined 26 years (1995-2020) of photo-identification, behavioural, (epi)genetic, and endocrine data from an endangered population of humpback whales (New Caledonia), to explore male reproductive success, age, physiology, and population dynamics over almost a third of the lifespan of a humpback whale. First, I conducted a paternity analysis on 177 known mother-offspring pairs and confirmed previous findings of low variation in reproductive success in male humpback whales. Second, epigenetic age estimates of 485 males revealed a left-skewed population age structure in the first half of the study period that became more balanced in the second half. Further, older males (> 23 years) more often engaged in certain reproductive tactics (singing and escorting) and were more successful in siring offspring once the population age structure stabilised, suggesting reproductive tactics and reproductive success in male humpback whales may be age-dependent. Third, using enzyme immunoassays on 457 blubber samples, I observed a seasonal decline in male testosterone in the population over the breeding season. Testosterone levels appeared highest during puberty, then decreased and levelled off at the onset of maturity, yet were highly variable at any point during the breeding season and across males of all ages. Lastly, I investigated the influence of genetic diversity at the major histocompatibility complex (MHC) class I and class IIa (DQB and DRB-a) on patterns of male reproductive success in humpback whales. Mating pairs shared fewer alleles than expected under random mating at MHC class I and IIa, thus, providing evidence of an MHC-mediated female mate choice in humpback whales. This thesis provides novel, critical insights into the evolutionary consequences of commercial whaling on the demography, patterns of reproduction and sexual selection of exploited populations of baleen whales.
Human activities are linked to increasing pollution of water, air, and land. This pollution of the environment creates harmful effects on the organisms inhabiting the ecosystem within such localities. The increasing global population with the pressures of immigration to urban centers has created a frightening increase of urban population globally, rising from 751 million in 1950 to 4.5 billion in 2018. The pressure to feed this populace, provide goods and services to meet human needs has birthed unprecedented rise in commerce and industries of different kinds, making the cities of the world to contribute 60% to total global greenhouses gases emissions thereby polluting the air. The resultant greenhouse gases induced depleting effects on the ozone layer, have facilitated climate change with its attendant harmful characteristics, on the environment, ecosystems, and ultimately man. Greenhouse gases and other air pollutants are the central theme of climate change. This chapter has examined the impacts of air pollution on human health on short- and long-terms basis as well as on the environment such as acid rains, decreases/increases in rainfall and its impacts on crops cultivation, migratory pattern of birds, incidences of diseases vectors, flooding and drought with attendant ecological consequences on humans, crops, animals breeding and growth, and social-economic services. Changes in climatic conditions have been shown to affect animals and plants, while also tampering with income of farmers, while scarcity of water is shown to create conflicts between farmers and herders in rural communities, thereby creating social-political tensions in several demographics. The long-term impacts lie in the biodiversity loss, which distorts ecological dynamics in a manner that threatens humans, ecosystems/environment and ultimately the earth we all share. From this understanding, strategies to stem biodiversity loss and move toward cleaner ambient air were discussed and recommended.
An investigation on population structure and ecology of the African elephants ( Loxodonta africana ) was carried out in Chebera Churchura National Park, Ethiopia during the wet and dry seasons of 2020 –2021. Sample counts using distance sampling of the African elephants were carried out in an area of 1, 410 km ² . The total population estimated was 756 individuals, and the mean population density estimated was 0.53/km ² . Among these, females constituted 52.12% and males 36.07%. The remaining 11.8% of the population was young of both sexes. It was difficult to categorize the young into male and female in the field, as their primary sexual characteristics were not easily visible.
Male to female sex ratio was 1.00:-1.42. Age structure was dominated by adults, which constituted 53.83% of the total population. Sub-adults comprised 19.11%, juveniles contributed 15.18% and calves accounted for 12.11% of the population. The herd size ranged from 1 to 149 individuals and the mean herd size during wet and dry seasons were 16.5 and 50.25, respectively. The African elephants were distributed in four habitat types: grassland, woodland, montane forest and riverine habitats in the study area. They were observed more in the riverine vegetation types during the dry season. Relative abundance of food resources, green vegetation cover and water availability in the area were the major factors governing their distribution in the present study area.
The introduction of elephants into new groups is necessary for breeding programmes. However, behavioural studies on the reactions of these animals at first encounters are missing. In the present study, female African elephants (Loxodonta africana) living in zoos were observed during unifications with unfamiliar elephants (introduction of two to one females and one to two females; n = 6) and reunifications with related elephants (two mother–daughter-pairs; n = 4) that were separated for 2 and 12 years, respectively. First encounters of the elephants were observed and recorded by scan sampling. The parameters measured were (a) signs of the characteristic Greeting Ceremony, (b) distance to the fence separating the elephants during first contact, and (c) time until trunks touched for the first time. The data were statistically analysed with SPSS. The results showed that related elephants performed a full Greeting Ceremony on reunifications. Unrelated elephants only expressed a minor greeting. During first encounters, related elephants predominantly showed affiliative behaviour (p = 0.001), whilst unrelated elephants expressed more agonistic behaviour (p = 0.001). The distance to the fence was significantly smaller for related elephants than for unrelated elephants (p = 0.038). first contact of trunks occurred on average after 3.00 s. in related elephants and 1026.25 s. in unrelated elephants. These findings indicate that related elephants recognise their kin after up to 12 years of separation, meet them with a full Greeting Ceremony during reunification, and seek contact to the related elephant, while unrelated elephants are hesitant during unifications with unfamiliar elephants and express more agonistic behaviour. The results testify that zoo elephants show the same species-specific social behaviour as their conspecifics in the wild. It also confirms the cognitive abilities of elephants and the significance of matrilines for breeding programmes.
Coercive mate guarding, where males use aggression to control female movements, is a form of sexual coercion which functions to constrain female mate choice. Non-human primates, for example, herd females to keep them away from competing males, but male bottlenose dolphins (Tursiops aduncus) also herd females to keep them close to their alliance partners. Indeed, pairs and trios of male dolphins work together to sequester single estrus females and defend them from competing alliances. Yet how males facilitate such coordination remains unknown. Here, we investigate the vocal behaviour of allied male bottlenose dolphins during the herding of individual females, examining how the production of whistles and 'pops' (a threat vocalisation) varied with behavioural state and inter-animal distances. Allied males produced both whistles and pops significantly more often and at higher rates during social interactions, though they differed in function. Whistle rates increased significantly when new individuals joined the consorting group, consistent with previous work showing that whistles are part of a greeting sequence for this species. Whistle matching also appeared to play a role in within-alliance coordination. Pop vocalisations increased significantly when the nearest male to the female changed, likely inducing the female to remain close as the males coordinate a guard switch. Building upon prior research examining female movements in response to pops, we show that males approach the female and current guard whilst popping, leading to a guard switch. Our results provide new insights into the use of vocal signals during cooperative mate guarding between allied male dolphins.
Coercive mate guarding, where males use aggression to control female movements, is a form of sexual coercion which functions to constrain female mate choice. Non-human primates, for example, herd females to keep them away from competing males, but male bottlenose dolphins (Tursiops aduncus) also herd females to keep them close to their alliance partners. Indeed, pairs and trios of male dolphins work together to sequester single estrus females and defend them from competing alliances. Yet how males facilitate such coordination remains unknown. Here, we investigate the vocal behaviour of allied male bottlenose dolphins during the herding of individual females, examining how the production of whistles and ‘pops’ (a threat vocalisation) varied with behavioural state and inter-animal distances. Allied males produced both whistles and pops significantly more often and at higher rates during social interactions, though they differed in function. Whistle rates increased significantly when new individuals joined the consorting group, consistent with previous work showing that whistles are part of a greeting sequence for this species. Whistle matching also appeared to play a role in within-alliance coordination. Pop vocalisations increased significantly when the nearest male to the female changed, likely inducing the female to remain close as the males coordinate a guard switch. Building upon prior research examining female movements in response to pops, we show that males approach the female and current guard whilst popping, leading to a guard switch. Our results provide new insights into the use of vocal signals during cooperative mate guarding between allied male dolphins.
Power in Close Relationships - edited by Christopher R. Agnew February 2019
Darwin's1 hypothesis that male secondary sexual ornaments evolve through female preferences is theoretically plausible2-7, but there is little experimental field evidence that such preferences exist8-10. I have studied female choice in relation to male tail length in the long-tailed widowbird, Euplectes progne, and report here that males in which the tail was experimentally elongated showed higher mating success than males having normal or reduced tails. The possibility that intrasexual competition among males maintains the long tail was not supported: males with shortened tails held their territories as long as did other males. These results suggest that the extreme tail length in male long-tailed widowbirds is maintained by female mating preferences.
The suckling behaviour of 130 freeranging elephant calves aged between birth and 4.5 years old was examined in Amboseli National Park, Kenya. Analyses of frequencies of suckling and durations of suckling bouts showed that males attempted to suckle more often, were more successful at their attempts, and as a result were estimated to have a higher milk intake than did female calves. Mothers were equally tolerant of their sons' and daughters' demands to suckle at young ages, but were less tolerant of their older sons' demands. The growth rates of males based on hind footprint length were faster than those of females from birth onwards. During drought years with low food availability, male calf survivorship in the first year was lower than that of female calves. During wet years, there was little difference between sexes in survivorship. It appeared that during dry years mothers were unable to sustain milk production at a level that met the metabolic requirements of their sons, and as result male calves were more likely to die. Females with a surviving son tended to have a longer interbirth interval than did females with a surviving daughter. We suggest that greater early maternal investment in male calves occurs because, in the highly-competitive polygynous mating system of elephants, size in adult male elephants is an important factor in mating success.
Male-male competition and reproductive success of northern elephant seals, Mirounga augustirostris, was studied for six consecutive breeding seasons at Año Nuevo Island, California. The conclusions were as follows: (i) Less than one third of the males in residence copulate during a breeding season. A few males are responsible for the majority of copulations, (ii) The number and age of males copulating varies with: (a) harem location and topography, (b) the number of estrous females in the harem, and (c) the number of males competing for females, (iii) Copulation frequency is related directly to success in male-male competition, i.e., social rank. (iv) The same individuals may dominate breeding for three consecutive breeding seasons. (v) Successful males die within a year or two after their reproductive peak. (vi) The reproductive success of most males is nil or low because many die before reaching breeding age and some of those that reach maturity are prevented from mating by the highest ranking males. (vii) Individual strategies have important consequences for reproductive success, (viii) Male-male competition is a major cause of pup mortality prior to weaning.
The potential reproductive success of males is much greater than that of females. Changes in colony number and composition affect the reproductive success of males as well as females.
The phenomenon of musth in male Asian elephants, Elephas maximus, has
long been recognized1. Musth, which has been likened to
rutting behaviour in ungulates2, refers to a set of physical
and behavioural characteristics displayed periodically by adult male
elephants. The most obvious manifestations are a sharp rise in
aggressive behaviour, copious secretions from and enlargement of the
temporal glands, and the continuous discharge of urine3. It
has been speculated that a similar phenomenon occurs in males of the
African genus, Loxodonta africana, but most workers have concluded that
it does not exist4-7. Here we show that musth does occur in
the African elephant and that its manifestations are similar to those in
the Asian elephant.
Bulls in musth leave their home range, travel far and fast, initiate more contacts with distant breeding herds, show aggression which overrides normal social male hierarchies, probably mate more frequently than non-musth bulls and then return to their home range. This behaviour is associated with elevated levels of serum testosterone and dihydrotestosterone. Elephants normally show a high degree of fidelity to sexually segregated adjoining home ranges, which results in regular contact between the same bulls and cows. This breeding strategy is applicable to older, dominant bulls within the locally resident hierarchy. The musth adaptation is a second strategy, whereby younger, lower ranking bulls (25-35 yr) can ensure more contacts with cows and maximize their chances of breeding. Because musth bulls mate far from their normal ranges the strategy promotes gene flow and ensures outbreeding. -from Author
The possibility that the evolution of mating preferences and secondary sex traits can be based on heritable differences in viability is examined with a three-locus model. Earlier genetic models suggested that viability-based processes alone cannot explain the evolution of mate choice and sex ornaments that reduce survival; a Fisherian mating advantage seemed necessary. The present model is based on a monogamous mating system that precludes such a mating advantage. A key assumption is that ornament development depends on the phenotypic condition and overall genotype of the possessor; there is evidence that secondary sex traits often mirror nutritional status and health, sometimes through hormonal mediation. Ornament and preference can then hitchhike slowly to high frequency with alleles that confer a slight survival advantage, provided that such alleles become available often enough. The evolution of mating preferences and secondary sex traits that reflect overall genotypic constitution therefore can be based solely on viability differences, no Fisherian mating advantage being required. In practice, these and several other mechanisms of sexual selection may occur together.
Loxodonta africana were studied in National Park, Kenya. Five categories of oestrous behaviour are described: wariness, the oestrous walk, the chase, mounting, and consort behaviour. On average Amboseli females conceived once every 5 yr; for each of these conceptions the female may only have been in oestrus (lasting 2-6 days) once. Some females may exercise choice in mating partners. Possible short-term advantages to females exercising choice in mating partners are avoidance of harassment from other bulls; and large males in musth may be more likely to impregnate a female. A possible long-term advantage to mating with a large (older) male could be his ability to pass on a trait for longevity. Although females may be exercising choice among the size/age classes, male-male competition among the large males may override female choice on the individual level.-from Author
The reproductive behaviour of a population of individually marked toads Bufo bufo was studied at a pond where males outnumbered females by between four and five to one. There was intense competition between the males for mates and only 20·5 % of them bred successfully. Of the successful males, 38·5 % got mates by fighting and displacing other males from the backs of females (takeovers). Larger males enjoyed greater reproductive success because they were stronger and better able to achieve takeovers. When competing for females, some males searched at the spawn site while others searched away from spawn. The numbers searching in the two areas can be predicted by a model which assumes that unpaired males distribute themselves so that there is a spatial ESS, where individuals have equal expectations of finding a female both at and away from the spawning ground.
Females that mate with the most fit male available leave more viable offspring than females that mate with males of lesser fitness. We describe a mechanism by which females facilitate mating with a superior genotype, as reflected by age, social rank, and sexual experience, without exerting choice. Female elephant seals increase the probability of mating with a mature, high-ranking male by simply rejecting all copulatory attempts during early estrus. Females protest loudly when mounted; this signals all nearby males and activates the dominance hierarchy. The probability that the mounting male will be interrupted by another male is a function of the mounter's social rank. The lower his rank, the higher the probability of interruption. The result is that mature males of high social rank have more time and freedom to attempt copulation, and they succeed in doing most of the mating. The behavior of the female intensifies this monopoly by making it more difficult for young, subordinate males to copulate. A similar female strategy seems to operate in several species where the female is courted by several males. Influencing the genotype of her offspring is an important means by which a female can increase her inclusive fitness. This aspect of sexual selection has been neglected.
Male Loxodonta africana spent more time in association with females during musth than during non-musth periods. Males were more aggressive during their musth periods. Occurrence and duration of musth were age-related: no male under 24 yr was seen in musth; bouts of musth among younger individuals were short and sporadic, while older males experienced longer more predictable periods of musth on an annual basis. Males in musth were observed year-round, but frequency of musth males was highest during and following the 2 rainy seasons and, in general, good rainfall years had higher frequencies of males in musth than did poor rainfall years. Number of males in musth per month correlated closely with the number of females observed in estrus, but since estrus lasts only 4-6 days, while musth may last several months, onset of musth was not necessarily triggered by onset of estrus in a particular female. The musth periods of different males were asynchronous and each male came into musth at a specific time of year. This period was relatively consistent from one year to the next, particularly among older males. Males in musth advertised their heightened sexual and aggressive state through visual and olfactory signals and by vocalizing. These signals announce identity, condition and location to both rival males and to potentially receptive females. The physical and behavioral characteristics and temporal patterning of musth are very similar in African and Asian elephants. -from Author
Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
Calls at frequencies below the range of human hearing were recorded from two groups of captive Asian elephants (Elephas maximus). Most of the calls ranged in frequency from 14 to 24 Hz, with durations of 10–15 s (Fig. 1). With the nearest elephant 5 m from the microphone, sound pressure levels were 85 to 90 dB (re 20 Pa). These calls occurred in a variety of circumstances. Elephants are the first terrestrial mammals reported to produce infrasound. These calls may be important in the coordination of behavior in thick vegetation or among separated groups of elephants.
The calls of male field crickets attract sexually receptive females. In Gryllus integer, males differ from one another in their durations of uninterrupted calling (calling bout lengths). Tape recordings of the calls of 50 wild-caught males revealed that 14 males spent most of their calling time in short bouts (Fig. 1A), 18 in both short and long bouts (Fig. 1B), and 18 in long bouts (Fig. 1C). Re-recordings of 32 males after 3 weeks showed that calling bout lengths of individual males are stable with time (age) (Fig. 2). Three phonotaxis experiments investigated whether calling bout lengths of males affect female preferences. They demonstrated that (1) females can discriminate among conspecific males on the basis of calls alone; (2) females are preferentially attracted to males with long calling bout lengths; and (3) calling bout length is the specific factor responsible for preferential attraction. These results precisely identify a criterion that females use to discriminate among potential mates of their own species.
Experiments were designed to determine the effects of male pigmentation patterns on female choice in guppies. When presented with a series of variably-colored males, females of different genetic strain consistently exhibited similar preferences (Tables 1 and 2), preferring those males with the greatest development of both carotenoid and iridescent pigments (Table 3). A partial rank correlation analysis of pigments of males indicates positive correlations between the iridescent and carotenoid pigments and also between melanins and showiness (Table 4). Only when either the carotenoid or iridescent pigments were held constant was there any effect of the other pigments on the ranking order of males by the females. Other pigments appear to be relatively unimportant in influencing female choice of males. These results indicate that females discriminate among males on the basis of color and that females of different strains prefer the same male colors rather than those characteristics of males of their own strain. The results support those models of sexual selection that hold that sexually selected traits honestly advertise the phenotypic and genetic qualities of males; they do not support models of runaway selection for particular male traits, such as first proposed by Fisher (1930).
Several types of low frequency calls made by African elephants, Loxodonta africana, and the contexts in which they occurred are described. These calls had fundamental frequencies ranging from 14–35 Hz and sound pressure levels as high as 1033dB (re 20 Pa) at 5 m from the source. Very low frequency sounds are subject to very little environmental attenuation, suggesting that sounds at the frequencies and sound pressure levels measured from elephants may be audible to conspecifics several km away. Long-term records on the behavior of elephants and on the contexts of specific call types suggest that elephants make use of infrasound in the spatial coordination of groups and as they search for mates.
The evolution of female choice is controversial. The males of many polygynous species have bizarre features such as long and elaborate tails which seem to be maladaptive. If females choose to mate with such males how could choice genes increase in frequency? It is argued that (a) male age may be an indicator of fitness with older males having a higher average fitness than young males, (b) the size and complexity of many male ornaments and weapons are positively correlated with age. Females that choose males with, say, a longer than average tail are choosing males who are older than average. The choosy females therefore have male and female offspring with a higher fitness than the progeny of randomly mating females. As female choice genes spread the size or complexity of the age-dependent ornament increases. Mutations increasing size or complexity of such ornaments will also spread. A stable situation will be reached when the advantage of choosing older males is balanced by the disadvantage of, say, very long tails.
Predictions derived from game theory suggest that animals should not signal their intentions during conflict situations. However, during the period of musth, male elephants,Loxodonta africana, announce a state of heightened aggression with signals that are unbluffable. Since smaller musth males in poor condition are able to dominate larger, normally higher-ranking, non-musth males in good condition, musth provides a useful system with which to examine the possibility of honest signalling of motivation, rather than of fighting ability. Despite the highly aggressive state of males in musth, escalated contests are extremely rare. The behaviour of musth and non-musth males suggests that opponents are able to estimate their often rapidly changing roles in the asymmetries with relative accuracy. Since, unlike most other rutting mammals, elephants have asynchronous sexually active periods, resource value varies both with age and the fluctuating sexual state of a particular individual. It is suggested that musth may be a case where information about resource value is conveyed.
For red deer stags, fighting both has appreciable costs and yields considerable benefits. Up to 6% of rutting stags are permanently injured each year, while fighting success and reproductive success are closely related, within age groups as well as across them. Fighting behaviour is sensitive to changes in the potential benefits of fighting: stags fight most frequently and most intensely where potential benefits are high and tend to avoid fighting with individuals they are unlikely to beat. The relevance of these findings to theoretical models of fighting behaviour is discussed.
BECAUSE the primates are a particularly well studied group they provide
a rare opportunity to investigate the adaptive significance of species
differences in sexual dimorphism in body size. We describe here an
investigation of the relationship between the degree of sexual
dimorphism and three variables which are predicted might affect it.
Combination of seven surveys of blood parasites in North American passerines reveals weak, highly significant association
over species between incidence of chronic blood infections (five genera of protozoa and one nematode) and striking display
(three characters: male "brightness," female "brightness," and male song). This result conforms to a model of sexual selection
in which (i) coadaptational cycles of host and parasites generate consistently positive offspring-on-parent regression of
fitness, and (ii) animals choose mates for genetic disease resistance by scrutiny of characters whose full expression is dependent
on health and vigor.
Observational study of behavior: sampling methods
- Atlmann
On the ecology and behaviour of the African elephant
- Douglas-Hamilton
Musth and male-male competition in the African elephant
- Poole