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A study was undertaken of a unique sample of 63 wild vervet monkeys Cercopithecus aethiops from a single population in Uganda collected over 35 days in 1947. Twenty-five were immature (12 females and 13 males) and 38 were adults (16 females and 22 males). Body mass, external measurements, masticatory and other masses were recorded for each individu...
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A study was undertaken of a unique sample of 63 wild vervet monkeys Cercopithecus aethiops from a single population in Uganda collected over 35 days in 1947. Twenty-five were immature (12 females and 13 males) and 38 were adults (16 females and 22 males). Body mass, external measurements, masticatory and other masses were recorded for each individu...
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... In vervet monkeys, the sexes are dimorphic with males on average 1.4 times the weight of females (Turner et al., 2018), more muscular, and with canines on average 1.3 times the length of those of females (Bolter and Zihlman, 2003). Males disperse from the natal group when they reach sexual maturity (around 4 to 5 years-old), and subsequently disperse multiple times in their lifespan (Cheney and Seyfarth, 1990). ...
Females dominate a subset of the males in a minority of mammalian species despite male-biased sexual dimorphism. How this may arise is suggested by a computational model, DomWorld. The model represents male-biased sexual dimorphism through the males’ greater initial dominance and higher intensity of aggression, meaning that fights initiated by males have a greater impact than those by females. The model shows that female dominance over males increases with a greater proportion of males in the group. This happens because when males are involved in a larger fraction of fights this results in greater hierarchical differentiation (i.e., steepness). This causes rank overlap between the sexes (i.e., partial female dominance). We test the validity of these processes in vervet monkeys (Cercopithecus pygerythrus), a primate species with partial female dominance. We confirm that the proportion of males in the group is significantly positively correlated with the degree of dominance by females over males and with the steepness of the hierarchy among males exclusively, but not with the steepness of the hierarchy among all adults of the group. The steepness in male hierarchies correlated positively with female dominance over males in these groups. We show that steeper hierarchies among vervet males resulted from male-to-male fights being a larger proportion of the fights among all adults of the group. We conclude that the higher frequency of male intrasexual aggression favors female dominance in vervet monkeys. We also show that females received coalitionary support when they were in conflict with a male, mainly from other females, and that this favors female dominance in this species, but this does not explain why partial female dominance increased with the proportion of males in the group. We advocate further investigation of the influence of male intrasexual aggression on the degree of female dominance over males in other species with partial female dominance.
... Females are considered to be adults earlier than males, usually around their first conceptions (i.e., 4 years of age: Bolter & Zihlman, 2006). Our study relied on a long-term data set which includes Vervet monkeys engage in nonrandom dispersal, which can be initiated several times in an individual's lifetime, whereby intergroup movement is affected by several factors (Cheney & Seyfarth, 1983). ...
... To investigate whether males timed their transfers to reduce risks of inbreeding, we compared each subadult male's known age at natal dispersal to the mean male age at sexual maturity (i.e., 60 months; Bolter & Zihlman, 2006). For adult males and secondary dispersals, we compared male tenure length to females' mean age at first conception (i.e., 42.4 months; Harvey & Clutton-Brock, 1985). ...
Dispersal between social groups reduces the risk of inbreeding and can improve individuals' reproductive opportunities. However, this movement has costs, such as increased risk of predation and starvation, loss of allies and kin support, and increased aggression associated with entering the new group. Dispersal strategies, such as the timing of movement and decisions on whether to transfer alone or in parallel with a peer, involve different costs and benefits. We used demographic, behavioral, hormonal, and ecological data to examine the causes and consequences of 36 dispersal events from 29 male vervet monkeys (Chlorocebus pygerythrus) at Lake Nabugabo, Uganda. Adult males' secondary dispersal coincided with the conception season in females, and males improved their potential access to females by moving to groups with higher female-to-male sex ratios and/or by increasing their dominance rank. Males that dispersed with a peer had lower fecal glucocorticoid and androgen metabolite levels than lone dispersers. Subadult males were not more likely to engage in parallel dispersals compared to adult males. Dispersal was also used as a mechanism to avoid inbreeding, but changes in hormone levels did not seem to be a trigger of dispersal in our population. Our findings illustrate the complex individual strategies used during dispersal, how many factors can influence movement decisions, as well as the value of dominance and hormone analyses for understanding these strategies.
... Smaller body size (Bolter & Zihlman, 2003;Dechow, 1983) and foraging party sizes (Butynski & de Jong, 2019;Sithaldeen, 2019) of vervets compared to baboons may also mean that guards often miss vervets when they enter the field. Researchers observing this field noticed that guards only responded to vervets in 15% of cases but to baboons in 85% of cases (Findlay & Hill, 2021b). ...
Foraging by wildlife on anthropogenic foods can have negative impacts on both humans and wildlife. Addressing this issue requires reliable data on the patterns of anthropogenic foraging by wild animals, but while direct observation by researchers can be highly accurate, this method is also costly and labor‐intensive, making it impractical in the long‐term or over large spatial areas. Camera traps and observations by guards employed to deter animals from fields could be efficient alternative methods of data collection for understanding patterns of foraging by wildlife in crop fields. Here, we investigated how data on crop‐foraging by chacma baboons and vervet monkeys collected by camera traps and crop guards predicted data collected by researchers, on a commercial farm in South Africa. We found that data from camera traps and field guard observations predicted crop loss and the frequency of crop‐foraging events from researcher observations for crop‐foraging by baboons and to a lesser extent for vervets. The effectiveness of cameras at capturing crop‐foraging events was dependent on their position on the field edge. We believe that these alternatives to direct observation by researchers represent an efficient and low‐cost method for long‐term and large‐scale monitoring of foraging by wildlife on crops. Understanding anthropogenic foraging by researcher observation is costly and labor‐intensive. We investigated whether camera traps and crop guard records could give the same insights as researcher observation into patterns of crop‐foraging by baboons and vervet monkeys. Camera and guard data predicted data from researchers for baboons, and to an extent, vervets, and therefore present a viable alternative to researcher observation allowing for large‐scale and long‐term monitoring of crop‐foraging.
... We relied on visible physical features that correspond to behavioural changes. The transition from infant to juvenile at twelve months is consistent with other observational studies (Seyfarth and Cheney 1986) and the relative timing of the first adult teeth (Bolter and Zihlman 2003). After twelve months, individuals are rarely carried or in nipple contact with their mother. ...
... Vervets are sexually dimorphic, thus females and males transition into sexual maturity at different times. Many studies agree that females reach sexual maturity at around three years old (Bramblett 1980;Horrocks 1985;Struhsaker 1967a, b), which is approximately when adult canines erupt in vervets (Bolter and Zihlman 2003;Turner et al. 1997). Thus, we used the presence of adult canines (visible when an individual yawns, eats, and plays) as an indicator of sub-adulthood for females. ...
... Thus, we used the presence of adult canines (visible when an individual yawns, eats, and plays) as an indicator of sub-adulthood for females. However, since males grow over a longer period than females and reach sexual maturity later (Bolter and Zihlman 2003;Bramblett 1980;Turner et al. 1997), it is more difficult to reliably determine their age class. Bolter and Zihlman (2003) found that males who had adult canines but had not yet achieved full adult dentition (36-42 months) had small, undescended testicles. ...
Increasingly, researchers are moving animal cognitive research into wild field settings. A field-based approach offers a valuable complement to laboratory-based studies, as it enables researchers to work with animals in their natural environments and indicates whether cognitive abilities found in captive subjects are generalizable to wild animals. It is thus important to field-based research to clarify which cognitive tasks can be replicated in wild settings, which species are suitable for testing in the wild, and whether replication produces similar results in wild animals. To address these issues, we modified a well-known lab test for field applications. The transfer index (TI) is a reversal learning task that tests whether animals rely on more associative or rule-based learning strategies (Rumbaugh in Primate behavior: developments in field and laboratory research. Academic Press, Inc., New York, pp. 2–66, 1970). In this paper, we detail changes needed to use a TI-like task in the field, here referred to as the Field Reversal Index (FRI). We tested a sample of nine wild vervet monkeys (Chlorocebus pygerythrus) on the FRI task at Lake Nabugabo, Uganda. We show that wild primates can successfully be tested on reversal learning paradigms, and present findings that reinforce previous conclusions from captive experiments. Our results indicate that vervets, like other cercopithecoids, rely on associative learning rather than rule-based learning. Further, our results are consistent with previous research that reports improved performance post-reversal in younger individuals relative to older individuals. The FRI enables researchers to test animals both in the wild and in captivity to facilitate direct comparisons between the learning abilities of captive and wild animals.
... Tooth presence, absence and gingival eruption information taken from casts and photographs were placed in order of tooth appearance to reveal the dental eruption sequence (see Supplemental Information). Published ages of dental eruption based on individuals of known age from captive and/or wild populations of the same species (Chlorocebus aethiops and Erythrocebus patas), or closely related species (Papio cynocephalus and Papio anubis) were used to estimate the chronological age of infant through young adult individuals in the Senegal populations [50,51,52,53,54]. See Supplemental Information for more information including age classes for NHPs used in this study. ...
Athropod-borne viruses (arboviruses) pose the greatest risk of spillover into humans of any class of pathogens. Such spillover may occur as a one-step jump from a reservoir host species into humans or as a two-step jump from the reservoir to a different amplification host species and thence to humans. Despite the widespread havoc wreaked by emerging arboviruses, little is known about their transmission dynamics in reservoir and amplification hosts. Here we used serosurveillance and mathematical modeling to elucidate the role of monkeys in the sylvatic, enzootic cycle of chikungunya virus (CHIKV). Over three years, 219 African green monkeys, 78 patas monkeys, and 440 Guinea baboons were captured in the region surrounding Kedougou, Senegal. The age of each animal was determined by anthropometry and dentition, and exposure to CHIKV was determined by detection of neutralizing antibodies. We estimate age-specific CHIKV seroprevalence, force of infection (FoI), and basic reproductive number ( R 0 ) in each species. Among the different species, CHIKV Fol ranged from 0.13 to 1.12 (95% CI, 0.81–2.28) and R 0 ranged from 1.5 (95% CI, 1.3–1.9) to 6.6 (95% CI, 5.1–10.4). CHIKV infection of infant monkeys was detected even when the virus was not detected in a concurrent survey of primatophilic mosquitoes and when population seropositivity, and therefore immunity, was too high for monkeys themselves to support continuous CHIKV transmission. We therefore conclude that monkeys in this region serve primarily as amplification rather than reservoir hosts of CHIKV. Additional efforts are needed to identify other vertebrate hosts capable of supporting continuous circulation.
... It represents the first archaeologically-recorded find of this species from the United Kingdom. Only the distal humerus epiphysis is fused, indicating the animal would have been between one and two years old (Bolter and Zihlman 2003;Washburn 1943). Pathology was noted on the skeleton with evidence of infection on the medial aspect of the right clavicle and a healed green stick fracture on the left fifth metacarpal. ...
This paper considers the faunal remains from recent excavations at the Royal London Hospital. The remains date to the beginning of the 19th century and offer an insight into the life of the hospital's patients and practices of the attached medical school. Many of the animal remains consist of partially dissected skeletons, including the unique finds of Hermann's tortoise (Testudo hermanni) and Cercopithecus monkey. The hospital diet and developments in comparative anatomy are discussed by integrating the results with documentary research. They show that zooarchaeological study of later post-medieval material can significantly enhance our understanding of the exploitation of animals in this period
... : External measurements; body and limb segments; 1 indicates the axial skin fold relative to distal humerus on the patas monkey. (4.3–6.6 kg, [10] [17] [19]) and the female at 3.5 kg similarly (2.9–5.8 kg, [17] [19]). Only the males are compared in muscle distribution and proportions to avoid the confounding variable of sex, and in the case of the patas female, age differences [19] [20]. ...
... : External measurements; body and limb segments; 1 indicates the axial skin fold relative to distal humerus on the patas monkey. (4.3–6.6 kg, [10] [17] [19]) and the female at 3.5 kg similarly (2.9–5.8 kg, [17] [19]). Only the males are compared in muscle distribution and proportions to avoid the confounding variable of sex, and in the case of the patas female, age differences [19] [20]. ...
... (4.3–6.6 kg, [10] [17] [19]) and the female at 3.5 kg similarly (2.9–5.8 kg, [17] [19]). Only the males are compared in muscle distribution and proportions to avoid the confounding variable of sex, and in the case of the patas female, age differences [19] [20]. ...
Patas monkeys (Erythrocebus patas) living in African savanna woodlands and grassland habitats have a locomotor system that allows them to run fast, presumably to avoid predators. Long fore- and hindlimbs, long foot bones, short toes, and a digitigrade foot posture were proposed as anatomical correlates with speed. In addition to skeletal proportions, soft tissue and whole body proportions are important components of the locomotor system. To further distinguish patas anatomy from other Old World monkeys, a comparative study based on dissection of skin, muscle, and bone from complete individuals of patas and vervet monkeys (Cercopithecus aethiops) was undertaken. Analysis reveals that small adjustments in patas skeletal proportions, relative mass of limbs and tail, and specific muscle groups promote efficient sagittal limb motion. The ability to run fast is based on a locomotor system adapted for long distance walking. The patas' larger home range and longer daily range than those of vervets give them access to highly dispersed, nutritious foods, water, and sleeping trees. Furthermore, patas monkeys have physiological adaptations that enable them to tolerate and dissipate heat. These features all contribute to the distinct adaptation that is the patas monkeys' basis for survival in grassland and savanna woodland areas.
... In polygynous mammals, males often mature later than females, and it has been hypothesized that in sexually dimorphic species in which males are the larger sex, males should reach sexual maturity, as well as adult body size, at an older age than females (Bolter and Zihlman 2003; Rubenstein 1993; Shea 1986). ...
Life history predicts that in sexually dimorphic species in which males are the larger sex, males should reach sexual maturity
later than females (or vice versa if females are the larger sex). The corresponding prediction that in sexually monomorphic
species maturational rates will differ little between the sexes has rarely been tested. We report here sex differences in
growth and development to adulthood for 70 female and 69 male wild owl monkeys (Aotus azarai). In addition, using evidence from natal dispersal and first reproduction (mean: 74mo) for 7 individuals of known age, we
assigned ages to categories: infant, 0–6mo; juvenile, 6.1–24mo; subadult, 24.1–48mo; adult >48mo. We compared von Bertalanffy
growth curves and growth rates derived from linear piecewise regressions for juvenile and subadult females and males. Growth
rates did not differ between the sexes, although juvenile females were slightly longer than males. Females reached maximum
maxillary canine height at ca. 2yr, about a year earlier than males, and females’ maxillary canines were shorter than males’. Thus apart from canine eruption
and possibly crown–rump length, the development of Azara’s owl monkeys conforms to the prediction by life history that in
monomorphic species the sexes should develop at similar paces.
KeywordsFirst reproduction–Growth rates–Ontogeny–Sexual monomorphism–von Bertalanffy growth model
... Body masses taken at the time of death prior to necropsy include brain and organs; we record individual body weights (Table I). We include the 6.5-yr-old as adult because he has the markers of adult: third molars (M3s) erupted and proximal humerus fused (after Bolter and Zihlman 2003). To behaviorists who study hylobatids in the wild, this age may at first appear to classify it as a subadult (Reichard and Barelli 2008), but in captivity monkeys and apes grow faster and mature earlier than their wild counterparts (Bolter and Zihlman 2010; Zihlman et al.2004). ...
... We measure cranial capacity (after Bolter and Zihlman 2003) using mustard seed and report it in cubic centimeters (cc). ...
Compared with the great apes, the small-bodied hylobatids were treated historically as a relatively uniform group with 2 genera, Hylobates and the larger-bodied Symphalangus. Four genera are now recognized, each with a different chromosome number: Hoolock (hoolock) (38), Hylobates (44), Nomascus (crested gibbon) (52), and Symphalangus (siamang) (50). Previous morphological studies based on relative bone lengths, e.g., intermembral indices; molar tooth sizes; and body masses did not distinguish the 4 genera from each other. We applied quantitative anatomical methods to test the hypothesis that each genus can be differentiated from the others using the relative distribution of body mass to the forelimbs and hind limbs. Based on dissections of 13 hylobatids from captive facilities, our findings demonstrate that each of the 4 genera has a distinct pattern of body mass distribution. For example, the adult Hoolock has limb proportions of nearly equal mass, a pattern that differentiates it from species in the genus Hylobates, e.g., H. lar (lar gibbon), H. moloch (Javan gibbon), H. pileatus (pileated gibbon), Nomascus, and Symphalangus. Hylobates is distinct in having heavy hind limbs. Although Symphalangus has been treated as a scaled up version of Hylobates, its forelimb exceeds its hind limb mass, an unusual primate pattern otherwise found only in orangutans. This research provides new information on whole body anatomy and adds to the genetic, ecological, and behavioral evidence for clarifying the taxonomy of the hylobatids. The research also underscores the important contribution of studies on rare species in captivity.
... For the vervets, gingival emergence times come from two vervet colonies on individuals of known age [33] [40]. The vervet age classes are revised from a previously published paper to allow comparison with the langurs [60]. Note that since dental growth is faster in captive versus wild primates, wild vervets' ages may be underestimated by as much as 9 months (based on M3 eruption in captive baboons 18 months earlier than in their wild counterparts [41], and baboons requiring twice the time to mature as vervets). ...
... Postcranial markers are added to the age class categories in order to separate immature from adult since the dentition completes growth before the postcrania (e.g., [46] [74]). The proximal humerus is the last long bone to fuse in monkeys [75], and this skeletal element divided immature from adult and serves as a marker for use across taxa (e.g., [44] [60]). ...
... To configure the percentage dental emergence completed in juveniles, eruption scores were added together and divided by the scores for adults (after [60]). To configure overall skeletal maturity in juveniles, the following 19 epiphyseal union scores were added together and divided by the scores for adults: proximal (p), medial, and distal (d) humerus; p and d radius, ulna, tibia, fibula, femur; greater and less trochanter of femur; three borders of the acetabulum and the ischiopubic ramus. ...
The physical growth patterns of crested langurs and vervet monkeys are investigated for several unilinear dimensions. Long bone lengths, trunk height, foot length, epiphyseal fusion of the long bones and the pelvis, and cranial capacity are compared through six dental growth stages in male Trachypithecus cristatus (crested langurs) and Cercopithecus aethiops (vervet monkeys). Results show that the body elements of crested langurs mature differently than those of vervets. In some dimensions, langurs and vervets grow comparably, in others vervets attain adult values in advance of crested langurs, and in one feature the langurs are accelerated. Several factors may explain this difference, including phylogeny, diet, ecology, and locomotion. This study proposes that locomotor requirements affect differences in somatic growth between the species.
