No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
The Behaviour and Ecology of the Orang-Utan (Pongo Pygmaeus)
Abstract
Between June 1968 and November 1971, 21 months of fieldwork were spent studying wild populations of orang-utans in Borneo and Sumatra. Fifteen hundred hours of daylight observation were made on these animals. In contrast to other higher primates, the dispersed distribution of food and the orang-utan's slow mode of travel seem to favour solitary habits. Over, 80 per cent of foraging units seen contined only one independent animal, either alone or with dependent young. Larger groupings were seen when adolescents joined up with other animals or when males and females formed temporary consortships for mating purposes. Comparison between several populations revealed an interesting mechanisms for the natural regulation of animal numbers. Differences between Bornean and Sumatran orang-utans are discussed in relation to the zoogeography of these two islands.
... Another potential source of isotopic variability derives from dietary variation, as orangutans obtain the majority of their body water from plants (Mackinnon, 1974). Plant oxygen isotope compositions can be stratified within tropical forest canopies (da Silveira et al., 1989;Roberts et al., 2017;Lowry et al., 2021)-potentially leading to offset values among various animals, including primates, that consume different resources in the same forest (Krigbaum et al., 2013;Nelson, 2013;Fannin and Scott McGraw, 2020). ...
... Plant oxygen isotope compositions can be stratified within tropical forest canopies (da Silveira et al., 1989;Roberts et al., 2017;Lowry et al., 2021)-potentially leading to offset values among various animals, including primates, that consume different resources in the same forest (Krigbaum et al., 2013;Nelson, 2013;Fannin and Scott McGraw, 2020). Orangutans forage at different canopy heights ranging from the ground to high in the canopy (Mackinnon, 1974;Ungar, 1996;Thorpe and Crompton, 2005;Ashbury et al., 2015). Mackinnon, 1974, reported that Bornean and Sumatran orangutans obtain 95% of their food from the middle and upper levels of the canopy, where preferred foods are most abundant. ...
... Orangutans forage at different canopy heights ranging from the ground to high in the canopy (Mackinnon, 1974;Ungar, 1996;Thorpe and Crompton, 2005;Ashbury et al., 2015). Mackinnon, 1974, reported that Bornean and Sumatran orangutans obtain 95% of their food from the middle and upper levels of the canopy, where preferred foods are most abundant. In contrast, Ungar, 1996, reported that Sumatran orangutans were quite variable in feeding heights, with a mean of approximately 19 m; lower than gibbons who fed preferentially in the high canopy. ...
Studies of climate variation commonly rely on chemical and isotopic changes recorded in sequentially produced growth layers, such as in corals, shells, and tree rings, as well as in accretionary deposits—ice and sediment cores, and speleothems. Oxygen isotopic compositions (δ ¹⁸ O) of tooth enamel are a direct method of reconstructing environmental variation experienced by an individual animal. Here, we utilize long-forming orangutan dentitions ( Pongo spp.) to probe recent and ancient rainfall trends on a weekly basis over ~3–11 years per individual. We first demonstrate the lack of any consistent isotopic enrichment effect during exclusive nursing, supporting the use of primate first molar teeth as environmental proxies. Comparisons of δ ¹⁸ O values (n=2016) in twelve molars from six modern Bornean and Sumatran orangutans reveal a high degree of overlap, with more consistent annual and bimodal rainfall patterns in the Sumatran individuals. Comparisons with fossil orangutan δ ¹⁸ O values (n=955 measurements from six molars) reveal similarities between modern and late Pleistocene fossil Sumatran individuals, but differences between modern and late Pleistocene/early Holocene Bornean orangutans. These suggest drier and more open environments with reduced monsoon intensity during this earlier period in northern Borneo, consistent with other Niah Caves studies and long-term speleothem δ ¹⁸ O records in the broader region. This approach can be extended to test hypotheses about the paleoenvironments that early humans encountered in southeast Asia.
... Another potential source of isotopic variability derives from dietary variation, as orangutans obtain the majority of their body water from plants (Mackinnon, 1974). Plant oxygen isotope compositions can be stratified within tropical forest canopies (da Silveira et al., 1989;Roberts et al., 2017;Lowry et al., 2021)-potentially leading to offset values among various animals, including primates, that consume different resources in the same forest (Krigbaum et al., 2013;Nelson, 2013;Fannin and Scott McGraw, 2020). ...
... Plant oxygen isotope compositions can be stratified within tropical forest canopies (da Silveira et al., 1989;Roberts et al., 2017;Lowry et al., 2021)-potentially leading to offset values among various animals, including primates, that consume different resources in the same forest (Krigbaum et al., 2013;Nelson, 2013;Fannin and Scott McGraw, 2020). Orangutans forage at different canopy heights ranging from the ground to high in the canopy (Mackinnon, 1974;Ungar, 1996;Thorpe and Crompton, 2005;Ashbury et al., 2015). Mackinnon, 1974, reported that Bornean and Sumatran orangutans obtain 95% of their food from the middle and upper levels of the canopy, where preferred foods are most abundant. ...
... Orangutans forage at different canopy heights ranging from the ground to high in the canopy (Mackinnon, 1974;Ungar, 1996;Thorpe and Crompton, 2005;Ashbury et al., 2015). Mackinnon, 1974, reported that Bornean and Sumatran orangutans obtain 95% of their food from the middle and upper levels of the canopy, where preferred foods are most abundant. In contrast, Ungar, 1996, reported that Sumatran orangutans were quite variable in feeding heights, with a mean of approximately 19 m; lower than gibbons who fed preferentially in the high canopy. ...
Studies of climate variation commonly rely on chemical and isotopic changes recorded in sequentially-produced growth layers, such as in corals, shells and tree rings, as well as in accretionary deposits—ice and sediment cores, and speleothems. Oxygen isotopic compositions (δ 18 O) of tooth enamel are a direct method of reconstructing environmental variation experienced by an individual animal. Here we utilize long-forming orangutan dentitions ( Pongo spp.) to probe recent and ancient rainfall trends on a weekly basis over ∼ 3–11 years per individual. We first demonstrate the lack of any consistent isotopic enrichment effect during exclusive nursing, supporting the use of primate first molar teeth as environmental proxies. Comparisons of δ 18 O values (n = 2016) in twelve molars from six modern Bornean and Sumatran orangutans reveal a high degree of overlap, with more consistent annual and bimodal rainfall patterns in the Sumatran individuals. Comparisons with fossil orangutan δ 18 O values (n = 955 measurements from six molars) reveal similarities between modern and late Pleistocene fossil Sumatran individuals, but differences between modern and late Pleistocene/early Holocene Bornean orangutans. These suggest drier and more open environments with reduced monsoon intensity during this earlier period in northern Borneo, consistent with other Niah Caves studies and long-term speleothem δ 18 O records in the broader region. This approach can be extended to test hypotheses about the paleoenvironments that early humans encountered in southeast Asia.
... In the 1800s, long before the terms flanged and unflanged were used, Alfred Russel Wallace identified these two male morphs as separate species (Wallace 1856a(Wallace , 1856b, an idea that may go back to Petrus Camper in the 1700s (Meijer 1991(Meijer , 2014. One hundred and twenty years later, instead of different species, these males were thought to represent different stages of development the same individual went through, with males who displayed secondary sex characteristics defined as adults and those who did not defined as subadults (MacKinnon 1974;Rijksen 1978;Mitani 1985;Galdikas 1985aGaldikas , 1985bSchürmann and van Hooff 1986;Utami et al. 1997;Fox 2002). More specifically, it was thought that, around age 8 or 10 years old, an orangutan male would shift from a juvenile stage of development to a "subadult" one during which they were sexually active but lacked secondary sex characteristics until reaching full adulthood around 14 or 15 years of age (MacKinnon 1974;Rijksen 1978), which is the average age of puberty for male orangutans (MacKinnon 1974; Morbeck and Zihlman 1988;Wich et al. 2004;Knott and Kahlenberg 2007). ...
... One hundred and twenty years later, instead of different species, these males were thought to represent different stages of development the same individual went through, with males who displayed secondary sex characteristics defined as adults and those who did not defined as subadults (MacKinnon 1974;Rijksen 1978;Mitani 1985;Galdikas 1985aGaldikas , 1985bSchürmann and van Hooff 1986;Utami et al. 1997;Fox 2002). More specifically, it was thought that, around age 8 or 10 years old, an orangutan male would shift from a juvenile stage of development to a "subadult" one during which they were sexually active but lacked secondary sex characteristics until reaching full adulthood around 14 or 15 years of age (MacKinnon 1974;Rijksen 1978), which is the average age of puberty for male orangutans (MacKinnon 1974; Morbeck and Zihlman 1988;Wich et al. 2004;Knott and Kahlenberg 2007). Although puberty itself is inconsistently defined, sometimes meaning the onset of secondary sexual characteristic development and at other times the start of adolescence (see Russon 2006 versus Knott and Kahlenberg 2007), adolescence is defined as weaned individuals showing some sexual activity between ages 8-14 and 10-14 years (Wich et al. 2004;Takeshita 2019). ...
... In contrast, it has been argued that adult unflanged males are under lower mate choice selection . In this regard, mating attempts by adult unflanged males are resisted by females more often than are those of flanged males (MacKinnon 1974;Galdikas 1985a;Sugardjito et al. 1987;Masterson and Leutenegger 1992;Mitra Setia et al. 2009;Utami Atmoko et al. 2009a). ...
Among extant great apes, orangutans are considered the most sexually dimorphic in body size. However, the expression of sexual dimorphism in orangutans is more complex than simply males being larger than females. At sexual maturity, some male orangutans develop cheek pads (flanges) while other males remain unflanged even after becoming reproductively capable. Sometimes flange development is delayed in otherwise sexually mature males for a few years. In other cases, flange development is delayed for many years or decades, with some males even spending their entire lifespan as unflanged adults. Thus, unflanged males of various chronological ages can be mistakenly identified as ‘subadults’. Unflanged adult males are typically described as “female-sized”, but this may simply reflect the fact that unflanged male body size has only ever been measured in peri-pubescent individuals. In this study, we measured the skeletons of 111 wild adult orangutans (Pongo spp.) including 20 unflanged males, 45 flanged males, and 46 females, resulting in the largest skeletal sample of unflanged males yet studied. We assessed long bone lengths (as a proxy for stature) for all 111 individuals and recorded weights-at-death, femoral head diameters, bi-iliac breadths, and long bone cross-sectional areas (as proxies for mass) for 27 of these individuals, including seven flanged males, three adults confirmed-unflanged males, and three young adult likely-unflanged males. ANOVA and Kruskal-Wallis tests with Tukey and Dunn post-hoc pairwise comparisons, respectively, showed that body sizes for young adult unflanged males are similar to those of the adult females in the sample (all p ≥ 0.09 except bi-iliac breadth), whereas body sizes for adult unflanged males ranged between those of adult flanged males and adult females for several measurements (all p < 0.001). Thus, sexually mature male orangutans exhibit body sizes that range from the female end of the spectrum to the flanged male end of the spectrum. These results exemplify that the term ‘sexual dimorphism’ fails to capture the full range of variation in adult orangutan body size. By including adult unflanged males in analyses of body size and other aspects of morphology, not as aberrations but as an expected part of orangutan variation, we may begin to shift the way that we think about features typically considered dichotomous according to biological sex.
... In the early 1960s, it became known that the orangutans has been threatened with extinction and the interest in orangutan suddenly increased [7] [8]. Indonesia and Malaysia both was put in place of legislation to protect the orangutan but, ironically, not its habitat [9]. ...
... According to [17], orangutans seem to have a low rate of grooming as compared to other apes and monkeys. [8] suggested that self-grooming usually occurred at the night, where the animals could not be observed. Similarly, grooming in captivity may happened in an early morning or late evening activity [17]. ...
... This was mostly due to the weather condition as animals usually became inactive and completely obscured in the early afternoon when the weather was hot. This is supported by the study done by [8], at which he suggested that weather played an important role in affecting daily activity patterns. Fig. 4 shows that, study subjects in semi-wild environment spent most of their time on the ground. ...
Although orangutan (Pongo pygmaeus) is one of Malaysian iconic species, however when compared to other great apes this species is not well studied. Several good articles regarding this species in captivity are relatively limited. Due to this reason, a behavioral study of this orangutan (P. pygmaeus) was conducted at Orang Utan Island, Bukit Merah, Perak. The main objectives of this study were to understand the ethology of orangutan in a semi-wild condition and the space utilization of the orangutans that would help in giving picture of the animal’s arboreal and terrestrial nature. Preliminary observations were carried out for five days in January 2016 and intensive observations was carried out for a month in February 2016. The observation method used was focal sampling with continuous reading. The observations were done by focusing on one individual subject for every one hour from 09:00 a.m. to 13:00 p.m. and from 14:00 p.m. to 17:00 p.m. The behavioral profile of the orangutans in semi-wild environment showed that resting, feeding, and playing are the three major daily activities of the orangutans on the island. In accordance with the purpose of this study, the result of the behavioral activities of orangutan can be used for the management and well-being of the orangutan in the study site. It is much hoped with the provided information this will help to increase our understanding of orangutans’ behavior in a semi-wild condition.
... However, more recently, Warren (2019) has proposed the use of a cognitive graph (or labeled graph) by humans, similar to topological maps constructed using a detailed metric system (Byrne 1979;Foo et al. 2005;Warren et al. 2017;Warren 2019;Ericson and Warren 2020). On the other hand, current evidence strongly suggests that most wild primates rely on a routebased mental map to navigate (Pongo pygmaeus : Mackinnon 1974; Ateles belzebuth and Lagothrix poeppigii: Di Fiore and Suarez 2007;Papio ursinus: Noser and Byrne 2007b; Propithecus edwardsi and Eulemur fulvus rufus: Erhart and Overdorff 2008; Alouatta palliata: Hopkins 2011; Saguinus fuscicollis weddelli: Porter and Garber 2013; Papio hamadryas: Schreier and Grove 2014;Papio ursinus: de Raad and Hill 2019). Additionally, some authors also have argued that both types of cognitive maps can be used, depending on environmental factors (Valero and Byrne 2007;Presotto and Izar 2010;Presotto et al. 2018). ...
... For example, Presotto et al. (2019) suggest that an environment with constant resource availability may induce primates to use topological navigation. In fact, some authors have argued that the repeated use of routes may act to connect sites with a higher density of feeding trees (Mackinnon 1974;Milton 1981Milton , 2000de Guinea et al. 2019) and help monitor future feeding sites (Di Fiore and Suarez 2007;Porter and Garber 2013). Moreover, route repetition seems to be greater in areas of the forest with higher canopy cover (Hopkins 2016;de Guinea et al. 2019) and/or in higher parts of the forest (de Guinea et al. 2019), facilitating the visual access to resources. ...
To increase efficiency in the search for resources, many animals rely on their spatial abilities. Specifically, primates have been reported to use mostly topological and rarely Euclidean maps when navigating in large-scale space. Here, we aimed to investigate if the navigation of wild common marmosets inhabiting a semiarid environment is consistent with a topological representation and how environmental factors affect navigation. We collected 497 h of direct behavioral and GPS information on a group of marmosets using a 2-min instantaneous focal animal sampling technique. We found that our study group reused not only long-route segments (mean of 1007 m) but entire daily routes, a pattern that is not commonly seen in primates. The most frequently reused route segments were the ones closer to feeding sites, distant to resting sites, and in areas sparse in tree vegetation. We also identified a total of 56 clustered direction change points indicating that the group modified their direction of travel. These changes in direction were influenced by their close proximity to resting and feeding sites. Despite our small sample size, the obtained results are important and consistent with the contention that common marmosets navigate using a topological map that seems to benefit these animals in response to the exploitation of clustered exudate trees. Based on our findings, we hypothesize that the Caatinga landscape imposes physical restrictions in our group’s navigation such as gaps in vegetation, small trees and xerophytic plants. This study, based on preliminary evidence, raises the question of whether navigation patterns are an intrinsic characteristic of a species or are ecologically dependent and change according to the environment.
... The uncertainties and validity of orangutan species identification are still debated (Ryder & Chemnick 1993). According to previous studies (MacKinnon 1974;Warren et al. 2001), some general external features can be used to distinguish between the two orangutan species. Red to deep maroon or blackish brown hair has been described as having been found on Bornean orangutans. ...
Rehabilitating and releasing orangutans back into the wild is one of the conservation strategies being pursued to conserve orangutans. However, the species determination between Sumatran, Tapanuli, and Bornean orangutans is essential for reintroduction to avoid outbreeding depression, which could lead to DNA hybridisation and increase the probability of recessive characters. Here, we reported on an investigation of three orangutans in which DNA forensic techniques were used to identify the species before release and reintroduction to their habitat. By applying DNA forensic, the orangutan was successfully confirmed with high probabilities (100%) by identifying two orangutan species, Pongo abelii and Pongo pygmaeus wurmbii. Based on ambiguous morphology, we found the possibility of orangutan species being misidentified in rehabilitation. This case report demonstrates the importance of molecular diagnostics to identify the orangutan species. We also provide workflow recommendations from genetic aspect for rehabilitated orangutans. These recommendations will enable decision-makers to consider genetics when assessing future management decisions, which will help ensure that the orangutan species is effectively conserved.
... Unlike humans, great apes exhibit pronounced canines, which are associated with sexual dimorphism, especially in gorillas and orangutans. Furthermore, great apes are primarily folivorefrugivorous (Gerstner & Pruetz, 2022;Mackinnon, 1974;Uwimbabazi et al., 2019;Wrangham et al., 1991), but differ in their dietary preferences. For instance, gorillas depend on terrestrial herbaceous vegetation (THV) when fruits are scarce (Doran et al., 2002;Masi et al., 2009;Watts, 1984). ...
Oral health is a crucial aspect of overall well‐being in both humans and nonhuman primates. Understanding the oral pathologies and dental conditions in apes can provide valuable insights into their evolutionary history, dietary habits, and overall health. The present study evaluates dental findings in wild great apes from museum specimens to gain insights into the influence of natural nutrition on dental health. Complete macerated skulls of wild, adult great apes from the collection of the Museum of Natural History, Berlin, Germany, were examined. We analyzed skulls of 53 gorillas ( Gorilla gorilla ), 63 chimpanzees ( Pan troglodytes ), and 41 orangutans ( Pongo spp.). For each skull, we recorded wear of dental hard tissues (Lussi and Ganss index), carious lesions, and periodontal bone loss. Incisal and occlusal dental hard tissue defects were found in all skulls, as well as considerable external staining. In all species, incisors and canines showed the greatest loss of tissue, followed by molars. The wear of molars decreased from the first to the third molars, premolars showed the least pronounced defects. Some individuals had apical osteolytic defects along with severe dental hard tissue loss with pulp involvement or after dental trauma, respectively ( n = 5). Our study did not observe any carious lesions among the examined great ape skulls. However, we did find evidence for localized or generalized periodontal bone loss in a subset of the specimens ( n = 3 chimpanzees, n = 7 orangutans). The natural diet and foraging behavior of great apes induces abrasion and attrition of dental hard tissue but does not yield carious lesions. The occurrence of periodontitis in individual apes indicates that the natural circumstances can induce periodontal bone loss even in the wild, despite physiological nutrition.
... For example, the differences in triquetrum shape between Pan and Gorilla might be related to differences in hand positioning during knuckle-walking [68,69]. For the highly arboreal hylobatids and Pongo, the differences in triquetrum shape might be linked to weight transfer through the ulnar side of the wrist in Pongo [70][71][72] and the frequent use of (ricochetal) brachiation of hylobatids [73][74][75]. This is supported by the LDA-UMAP, as Pan and Gorilla are separated into different clusters as well as Pongo and the hylobatids. ...
In this study, we tested the hypothesis that machine learning methods can accurately classify extant primates based on triquetrum shape data. We then used this classification tool to observe the affinities between extant primates and fossil hominoids. We assessed the discrimination accuracy for an unsupervised and supervised learning pipeline, i.e. with principal component analysis (PCA) and linear discriminant analysis (LDA) feature extraction, when tasked with the classification of extant primates. The trained algorithm is used to classify a sample of known fossil hominoids. For the visualization, PCA and uniform manifold approximation and projection (UMAP) are used. The results show that the discriminant function correctly classified the extant specimens with an F1-score of 0.90 for both PCA and LDA. In addition, the classification of fossil hominoids reflects taxonomy and locomotor behaviour reported in literature. This classification based on shape data using PCA and LDA is a powerful tool that can discriminate between the triquetrum shape of extant primates with high accuracy and quantitatively compare fossil and extant morphology. It can be used to support taxonomic differentiation and aid the further interpretation of fossil remains. Further testing is necessary by including other bones and more species and specimens per species extinct primates.
... Mannu and Ottoni (2009) described two incidents in which wild bearded capuchin monkeys attempted to club an opossum and a scorpion with a stick. Wild orangutans were observed breaking off branches and dropping or throwing them toward humans, other orangutans, and other species (Galdikas, 1982;Mackinnon, 1974;Schaller, 1961). At Tanjung Puting National Park, orangutans spontaneously hit conspecifics, humans, dogs, or monkeys with sticks (Galdikas, 1982); Kaja Island orangutans used a branch to club fish in shallow water and then caught and consumed them (Schuster et al., 2008:110, 128). ...
There is a popular idea that archaic humans commonly used wooden clubs as their weapons. This is not based on archaeological finds, which are minimal from the Pleistocene, but rather on a few ethnographic analogies and the association of these weapons with simple technology. This article presents the first quantitative cross-cultural analysis of the use of wooden clubs and throwing sticks for hunting and violence among foragers. Using a sample of 57 recent hunting-gathering societies from the Standard Cross-Cultural Sample, it is shown that the majority used clubs for violence (86%) and/or hunting (74%). Whereas in hunting and fishing the club usually served only as a secondary tool, 33% of societies used the club as one of their main fighting weapons. The use of throwing sticks was less frequent among the societies surveyed (12% for violence, 14% for hunting). Based on these results and other evidence, it is argued that the use of clubs by early humans was highly probable, at least in the simplest form of a crude stick. The great variation in the forms and use of clubs and throwing sticks among recent hunter-gatherers, however, indicates that they are not standardized weapons and that similar variation may have existed in the past. Many such prehistoric weapons may therefore have been quite sophisticated, multifunctional, and carried strong symbolic meaning.
... In general, available evidence suggests that Bornean orangutans cope well with low intensity logging (<5 trees/ha, e.g., RIL) with little to no change in density, but poorly with higher intensity logging (>5 trees/ha) where uncontrolled and illegal practices can cause high rates of incidental damage to non-felled tree and liana species (Johns 1988) that provide important food for orangutans (Alfred et al. 2010;Husson et al. 2009). At the onset of logging within their habitats, orangutans typically move into less disturbed patches of adjacent forests, which can result in an overcrowding of refugial habitats if they are already occupied at carrying capacity (Ancrenaz et al. 2004(Ancrenaz et al. , 2005(Ancrenaz et al. , 2010Davies 1986;MacKinnon 1971MacKinnon , 1974Marshall et al. 2006;Morrogh-Bernard et al. 2003). It is then likely that intense competition for limited resources would result in the competitive exclusion of some individuals, who would then disperse into other suboptimal habitats (if available) or die from starvation (van Schaik 2004). ...
The Northeast Bornean orangutan (Pongo pygmaeus morio) currently remains the only
orangutan subspecies for which extinction risks cannot be accurately assessed due to a severe lack of information around the habitat conditions and threats that its different population units experience. Despite decades of acknowledgement as a stronghold for the morio subspecies, the orangutan metapopulation in Kutai National Park (KNP) of East Kalimantan, Indonesia is one unit that remains to be adequately studied. This report presents a preliminary analysis of the threats to the orangutan subpopulation in the northeastern region of KNP using habitat assessments and observational notes of the human activities in and around this area. Current threats identified include industrial mining, agricultural activities and clear-cutting around this protected area, while illegal logging, fire sources and severe climate events threaten the interior forests. Poaching in relation to human-orangutan conflicts and negligent tourism practices were also identified as threats to the greater metapopulation in KNP. The results of this study can contribute to the foundation of information required to adequately assess and develop appropriate conservation efforts for the orangutan population unit of KNP.
----------------
Manuscript: https://yorkspace.library.yorku.ca/xmlui/bitstream/handle/10315/36857/MESMP03296.pdf?sequence=1&isAllowed=y
... Orangutan density (d) was estimated by adjusting nest density (d nest ) for three nest-related parameters using the equation: d = d nest /(p x r x t), to take into account the proportion of animals that actually build nests (p), the rate at which nests are produced (r), and the rate at which nests remain visible after construction (t) (van Schaik et al., 1995). The p and r parameters must be based on observed values from known populations (MacKinnon, 1974;Singleton, 2000;van Schaik et al., 1995), however there is no published literature on these parameters from our study site. As there has been no report of significant variation of proportion of nest builders among the three subspecies of Bornean orangutan, we used a p value of 0.9 which was generated by a long-term study in Gunung Palung, West Kalimantan (Johnson et al., 2005). ...
Abstract Of the three subspecies of Critically Endangered Bornean orangutans, Pongo pygmaeus pygmaeus has the smallest population size. One of its most important habitats is the tropical forest within and around Danau Sentarum National Park (DSNP). Research in the late 1990s estimated that ca. 1025 orangutans inhabited DSNP, while ca. 1717 orangutans inhabited the forest beyond DSNP's boundaries. However, concerns were later raised that incorrectly estimated nest decay rates (t values) may have led to the overestimation of the population size. Furthermore, the area experienced forest degradation and land use change between 2000 and 2013. Given these changing landscapes, updated population estimates were needed to inform policy makers and land‐use planners on the implications of habitat loss for resident orangutans. We conducted this study to recalculate nest decay rates based on current recommended methods, and to update our knowledge on the orangutan population in the region. Our average nest decay rate was 288.3 days; applying this to the study in the late 1990s generated estimates of 807 individuals within DSNP and 1578 beyond DNSP's boundaries. New surveys of the transects undertaken between 2010 and 2014 revealed that the population size had declined substantially in these two areas, to 202 and 71 individuals respectively. Both declines are considerable, but larger losses occurred in logged‐over and cleared forests outside the park. We discuss factors potentially driving these declines, emphasizing the need to improve habitat protection both inside and outside of DSNP, and make recommendations for improving the prospects for future orangutan conservation.
... Extant orangutans (Pongo pygmaeus, Pongo abelii, and Pongo tapanuliensis) are the most arboreal of the great apes and are representative members of evergreen tropical rain forest communities (MacKinnon 1974;Davies 1986;Payne and Prudente 2008;Nater et al. 2017). As such, in palaeontological reconstructions of paleoenvironments, the presence of orangutan specimens in fossil assemblages often indicates the existence of a forested habitat ( Van den Bergh et al. 2001;Storm et al. 2005;Tougard and Montuire 2006). ...
This report describes fossils recovered from Ganxian Cave in 2008 and 2018 by the Natural History Museum and Anthropology Museum of Guangxi. The cave sedimentary fill yielded rich mammalian fossils consisting mainly of isolated teeth of medium- to large-sized mammals (Primates, Proboscidea, Perissodactyla, Carnivora, Rodentia, Artiodactyla) of typical ‘Ailuropoda-Stegodon’ fauna, (e.g. Stegodon orientalis, Ailuropoda baconi, Pongo weidenreichi, Tapirus sinensis, Megatapirus augustus, Crocuta ultima), and more numerous extant species belonging to 28 taxa in total. The biochronological age of the fauna agreed with the age estimates obtained using Uranium–series and coupled ESR/U-series dating. Collectively, these results indicate a Ganxian fossil age range of 168.9 ± 2.4 ka to 362 ± 78 ka and establish Ganxian Cave as one of the most precisely dated Middle Pleistocene fossil sites in southern China. Comparison of Ganxian fauna with Pleistocene fossil records of the well-documented faunas of southern China and southeast Asia indicates that the Asian elephant (Elephas maximus) probably first appeared in Ganxian Cave. Paleoenvironmental reconstruction-based analysis of the large mammalian fossil assemblage from Ganxian Cave indicates that during the late Middle Pleistocene, the habitat consisted mainly of forests with some open areas and the climate was warm and humid.
... Bila dibandingkan antara INP pohon dengan pohon sarang, pohon Hoteng memiliki jumlah yang banyak dibandingkan dengan jenis pohon lainnya. Menurut MacKinnon (1974), orangutan membangun sarangnya akan memilih tempat yang berdekatan dengan pohon buah sumber pakannya, selain itu juga topografi daerah di sekitarnya. ...
Forest clearance for a variety of purposes and functions over the region led to the limited habitat for wildlife. Wildlife habitat is fragmented into several regions led to the survival of a population of a species depends on habitat conditions. The purpose of this study was to determine the population density of orangutans based on the number of nests in The results of this study indicate orangutan population density based on the number of nests in the Bulumario village and district CADS is 0,023 individuals/km 2 or 2,332 individuals/ha of the total number of nests found 49 nests. Most nests were found at a distance of 0-100 meters of the entire track the number of 14 nests (28,57%) and the class that dominates nest class D is the number of 23 nests (46,94%). Dominant position of the nest is in a position which is a position I nest close to the main stem of the tree with the nest number 24 (48,98%). Generally the nest is found at an altitude of 6-10 meters with a sum of 15 nests (30,61%). Important Value Index (IVI) is highest on the type Hoteng (Quercus gamelliflora Blume.) Of the family Fagaceae with IVI 33,83%, and the Moraceae family that is dominated by the number seven species.
... Although the female turned her body to face the male before VV mountings in some cases, which would have made VV mountings easier, it is unlikely that the female accepted VV mountings because similar behaviors were also observed when the female rejected the attempts by the male. Contrary to Japanese macaques, females actively invite males into VV mountings in apes (Breuer & Ndoundou Hockemba, 2007;Thompson-Handler et al., 1984), except in "sexual coercion" (Nadler, 1977), one of the common mating strategies by male orangutans (MacKinnon, 1974). The reason for this interspecific difference is unclear; however, it is possible either that this particular female was unfamiliar with VV mountings or that VV mountings and the behavior of the male pushing down the female imposed a great burden on her. ...
Ventro-ventral (VV) mountings during copulation are most dominant in humans. In contrast, nonhuman primates have a strong bias toward dorso-ventral mountings, and only apes have been known to show VV mountings during copulation between a pair of mature individuals. Reporting VV mountings during copulation in primates other than apes is critical to discussions regarding why VV mountings have been limited to apes among primates. Here, I report VV mounting in a mature male and female pair of provisioned Japanese macaques (Macaca fuscata). This is the first report of VV mountings during copulation by adult nonhuman primates without disabilities other than apes. The pair of monkeys performed VV mountings 13 times over a week. Following the mounting series, including VV mountings, the presence of a copulatory plug was confirmed around the female’s vagina, indicating that the VV mountings were part of their copulatory behaviors. The male initiated all VV mountings, and the female was often uncooperative during these attempts. In all cases, the female was lying on her back, and the male was on top. The pair were in close contact and did not see each other’s faces during VV mountings. This report suggests that eye contact between mates and morphological characteristics are the primary reasons for the evolution of VV mountings during copulation in apes.
... Only a few studies so far have reported behavioral observations on the use of non-visual senses in the evaluation of fruits. Studies in chimpanzees (Pan troglodytes), orangutans, (Pongo pygmaeus), gibbons (Symphalangus syndactylus), black-handed spider monkeys (Ateles geoffroyi), and squirrel monkeys (Saimiri sciureus) show that these species perform manipulative behaviors with their hands (palpations), through dental perception (taking small bites with incisors) or take exploratory bites into the fruits (taste), making use of their tactile and gustatory systems to evaluate the softness, size, shape, and taste properties of the fruits (Dominy et al. 2001;Kinzey and Norconk 1990;Laska et al. 2007;MacKinnon 1974;Marzke and Wullstein 1996;Pablo-Rodríguez et al. 2015;Valenta et al. 2015). Capuchin monkeys (Cebus imitator) and black-handed spider monkeys (A. ...
There is extensive knowledge about the visual system and the implications of the evolution of trichromatic color vision in howler monkeys (genus Alouatta) related to food selection; however, information about the other sensory systems is limited. In this study we assessed the use of touch, sniffing, and taste in fruit evaluation by 20 adult mantled howler monkeys (Alouatta palliata) on Agaltepec Island, Mexico. During 9 months of observation, we recorded the frequency that each monkey used touch, sniffing, and taste in evaluating cryptic fruits (that remain green during their ripening process) and conspicuous fruits (with red, yellow, or orange colorations when they are ripe). Sucrose content and hardness measurements were made to establish the degree of ripeness of the fruits. We found that mantled howler monkeys used long behavioral sequences during conspicuous fruit investigations. Sniffing was used infrequently, but significantly more often in the evaluation of conspicuous-ripe and unripe fruits compared to cryptic-ripe and unripe fruits. During the evaluation of cryptic-ripe fruits, mantled howler monkeys increased the use of touch compared to evaluating cryptic-unripe fruits. We did not find significant differences in the use of taste in the evaluation of cryptic and conspicuous fruits (both ripe and unripe). Our results suggest that the non-visual senses play an essential role in fruit selection by howler monkeys, with differences in the behavioral strategy according to the fruit's conspicuity. The multimodal signals of ripe and unripe fruits allow the howler monkeys to assess their palatability before being consumed.
... They can be defined as intentional movements of body parts like hands, limbs, or the head, and body postures that are directed toward another individual, are goal-directed, motorically ineffective (toward the recipient), and receive a voluntary response (Tomasello and Call, 2007). Gestures are used by great apes in the wild (MacKinnon, 1974;Goodall, 1986;Genty et al., 2009;Graham et al., 2017) and in captive settings (e.g., Tomasello et al., 1989;Pika et al., 2003Pika et al., , 2005Liebal et al., 2006). Examples of gestures in chimpanzees would be PRESENT BODY PART 2 (visual modality), TOUCH (tactile modality), and STOMP (auditory modality). ...
Symbolic communication is not obvious in the natural communicative repertoires of our closest living relatives, the great apes. However, great apes do show symbolic competencies in laboratory studies. This includes the understanding and the use of human-provided abstract symbols. Given this evidence for the underlying ability, the apparent failure to make use of it in the wild is puzzling. We provide a theoretical framework for identifying basic forms of symbolic signal use in chimpanzee natural communication. In line with the laboratory findings, we concentrate on the most promising domain to investigate, namely gesture, and we provide a case study in this area. We suggest that evidence for basic symbolic signal use would consist of the presence of two key characteristics of symbolic communication, namely arbitrariness and conventionalization. Arbitrariness means that the linkage between the form of the gesture and its meaning shows no obvious logical or otherwise motivated connection. Conventionalization means that the gesture is shared at the group-level and is thus socially learned, not innate. Further, we discuss the emergence and transmission of these gestures. Demonstrating this basic form of symbolic signal use would indicate that the symbolic capacities revealed by laboratory studies also find their expression in the natural gestural communication of our closest living relatives, even if only to a limited extent. This theoretical article thus aims to contribute to our understanding of the developmental origins of great ape gestures, and hence, arguably, of human symbolic communication. It also has a very practical aim in that by providing clear criteria and by pointing out potential candidates for symbolic communication, we give fieldworkers useful prerequisites for identifying and analyzing signals which may demonstrate the use of great apes’ symbolic capacities in the wild.
... Because orangutans are primarily frugivorous (MacKinnon 1974;Morrogh-Bernard et al. 2009;Russon et al. 2009), variability in habitat fruit abundance affects orangutans' association patterns. Differences between orangutan populations suggest that there is an evolved effect of long-term fruit abundance on association rates: orangutans living in more fruit-abundant habitats are more gregarious than those living in habitats with lower, or more seasonally variable, fruit abundance (Roth et al. 2020;Mitra Setia et al. 2009;). ...
As climate change continues to fundamentally alter resource landscapes, the ability to flexibly respond to spatio-temporal changes in the distribution of preferred food sources is increasingly important for the overall health and fitness of animals living in seasonal, variable, and/or changing environments. Here, we investigate the effects of an uncharacteristically long period of fruit scarcity, following widespread thick haze caused by peat and forest fires in 2015, on the behaviour and sociality of female Bornean orangutans ( Pongo pygmaeus wurmbii ). We collected data from 2010 to 2018 at Tuanan, Central Kalimantan, Indonesia, and compared the activity, diet, and association patterns of adult females during low-fruit periods before the fires, i.e., regular, seasonal periods of low fruit availability (“pre-fire”), and after the fires, i.e., during the extended period of low fruit availability (“post-fire”). First, we found that, post-fire, female orangutans adopted a more extreme energy-saving activity pattern and diet — resting more, travelling less, and diet-switching to less-preferred foods — compared to pre-fire. Second, we found that the probabilities of association between females and their weaned immature offspring, and between related and unrelated adult females were lower, and the probability of agonism between unrelated females was higher, post-fire than pre-fire. This change in energetic strategy, and the general reduction in gregariousness and social tolerance, demonstrates how forest fires can have lasting consequences for orangutans. Fission–fusion species such as orangutans can mitigate the effects of changes in resource landscapes by altering their (sub)grouping patterns; however, this may have long-term indirect consequences on their fitness.
Same-sex sexual behaviour (SSSB) occurs in most animal clades, but published reports are largely concentrated in a few taxa. Thus, there remains a paucity of published reports for most mammalian species. We conducted a cross-sectional expert survey to better understand the underlying reasons for the lack of publications on this topic. Most respondents researched Primates (83.6%, N = 61), while the rest studied Carnivora (6.9%, N = 5), Rodentia (4.1%, N = 3), Artiodactyla (2.7%, N = 2), and Proboscidea (2.7%, N = 2). Most respondents (76.7%, N = 56) had observed SSSB in their study species, but only 48.2% (N = 27) collected data on SSSB, and few (18.5%, N = 5) had published papers on SSSB. Of the unique species identified as engaging in SSSB in the survey, 38.6% (N = 17) have no existing reports of SSSB to the knowledge of the authors. In both the survey questions and freeform responses, most respondents indicated that their lack of data collection or publication on SSSB was because the behaviours were rare, or because it was not a research priority of their lab. No respondents reported discomfort or sociopolitical concerns at their university or field site as a reason for why they did not collect data or publish on SSSB. Multiple logistic regressions were performed to assess whether taxa studied, education level, or identification within the LGBTQ+ community predicted observing, collecting data on, or publishing on SSSB, but none of these variables were significant predictors. These results provide preliminary evidence that SSSB occurs more frequently than what is available in the published record and suggest that this may be due to a publishing bias against anecdotal evidence.
Vocal complexity is central to many evolutionary hypotheses about animal communication. Yet, quantifying and comparing complexity remains a challenge, particularly when vocal types are highly graded. Male Bornean orangutans ( Pongo pygmaeus wurmbii ) produce complex and variable “long call” vocalizations comprising multiple sound types that vary within and among individuals. Previous studies described six distinct call (or pulse) types within these complex vocalizations, but none quantified their discreteness or the ability of human observers to reliably classify them. We studied the long calls of 13 individuals to: (1) evaluate and quantify the reliability of audio-visual classification by three well-trained observers, (2) distinguish among call types using supervised classification and unsupervised clustering, and (3) compare the performance of different feature sets. Using 46 acoustic features, we used machine learning ( i.e. , support vector machines, affinity propagation, and fuzzy c-means) to identify call types and assess their discreteness. We additionally used Uniform Manifold Approximation and Projection (UMAP) to visualize the separation of pulses using both extracted features and spectrogram representations. Supervised approaches showed low inter-observer reliability and poor classification accuracy, indicating that pulse types were not discrete. We propose an updated pulse classification approach that is highly reproducible across observers and exhibits strong classification accuracy using support vector machines. Although the low number of call types suggests long calls are fairly simple, the continuous gradation of sounds seems to greatly boost the complexity of this system. This work responds to calls for more quantitative research to define call types and quantify gradedness in animal vocal systems and highlights the need for a more comprehensive framework for studying vocal complexity vis-à-vis graded repertoires.
Keywords: needing to learn hypothesis nest-building behaviour ontogeny selectivity skill learning Sumatran orang-utan trial-and-error practice Nest building is an important subsistence behaviour that young great apes must learn to become competent adults. Orang-utans show a remarkable degree of variability and selectivity for a broad range of features in their nest building. However, the details of when different aspects of nest-building skills emerge remain unclear. We used data on 27 immature Sumatran orang-utans and 20 mothers collected over a decade at Suaq Balimbing, Sumatra to investigate when immatures develop their nest-building skills and examine when nest tree species preferences emerge. We found that young orang-utans showed interest in nest building from 6 months of age and begin to construct day nests at around 1 year of age, whereas night nests were not practised until close to the third year of life. Nest-building practice peaked around age 3e4 years and then steadily decreased as immatures approached the age of nutritional independence, around age 8 years. By then, immature orang-utans were competent nest-builders, but their nests differed from adult nests in several aspects, such as fewer multitree nests and additional comfort elements, which seemed to be mastered later in development. All age classes demonstrated stronger selectivity towards tree species used for night nests and immatures eventually had similar preferences to mothers. We conclude that the ontogeny of nest-building behaviour and the selection of nest tree species in Sumatran orang-utans is a multiyear learning process that requires intense practice.
Humans and many other animal species act in ways that benefit others. Such prosocial behaviour has been studied extensively across a range of disciplines over the last decades, but findings to date have led to conflicting conclusions about prosociality across and even within species. Here, we present a conceptual framework to study the proximate regulation of prosocial behaviour in humans, non-human primates and potentially other animals. We build on psychological definitions of prosociality and spell out three key features that need to be in place for behaviour to count as prosocial: benefitting others, intentionality, and voluntariness. We then apply this framework to review observational and experimental studies on sharing behaviour and targeted helping in human children and non-human primates. We show that behaviours that are usually subsumed under the same terminology (e.g. helping) can differ substantially across and within species and that some of them do not fulfil our criteria for prosociality. Our framework allows for precise mapping of prosocial behaviours when retrospectively evaluating studies and offers guidelines for future comparative work.
Male orangutans (Pongo spp.) exhibit bimaturism, an alternative reproductive tactic, with flanged and unflanged males displaying two distinct morphological and behavioral phenotypes. Flanged males are larger than unflanged males and display secondary sexual characteristics which unflanged males lack. The evolutionary explanation for alternative reproductive tactics in orangutans remains unclear because orangutan paternity studies to date have been from sites with ex-captive orangutans, provisioning via feeding stations and veterinary care, or that lack data on the identity of mothers. Here we demonstrate, using the first long-term paternity data from a site free of these limitations, that alternative reproductive tactics in orangutans are condition-dependent, not frequency-dependent. We found higher reproductive success by flanged males than by unflanged males, a pattern consistent with other Bornean orangutan (Pongo pygmaeus) paternity studies. Previous paternity studies disagree on the degree of male reproductive skew, but we found low reproductive skew among flanged males. We compare our findings and previous paternity studies from both Bornean and Sumatran orangutans (Pongo abelii) to understand why these differences exist, examining the possible roles of species differences, ecology, and human intervention. Additionally, we use long-term behavioral data to demonstrate that while flanged males can displace unflanged males in association with females, flanged males are unable to keep other males from associating with a female, and thus they are unable to completely mate guard females. Our results demonstrate that alternative reproductive tactics in Bornean orangutans are condition-dependent, supporting the understanding that the flanged male morph is indicative of good condition. Despite intense male-male competition and direct sexual coercion by males, female mate choice is effective in determining reproductive outcomes in this population of wild orangutans.
In many group-living species, individuals are required to flexibly modify their communicative behaviour in response to current social challenges. To unravel whether sociality and communication systems co-evolve, research efforts have often targeted the links between social organisation and communicative repertoires. However, it is still unclear which social or interactional factors directly predict communicative complexity. To address this issue, we studied wild and zoo-housed immature orangutans of two species to assess the impact of the socio-ecological setting on the production of non-vocal signal repertoires. Specifically, we compared repertoire size, dyadic repertoire similarity, and number of social goals (i.e. observer’s estimate of the signaller’s intended interaction outcome) for communicative interactions with mothers versus other conspecifics, controlling for critical individual and environmental factors. In this small sample of immature orangutans, wild-captive contrasts were statistically significant only for other-directed repertoires, but not for mother-directed repertoires, and not for the number of social goals that immatures communicated towards. While the repertoires of individuals living in the same research setting were more similar than those living in contrasting settings, this difference was most pronounced for other-directed repertoires of the less socially tolerant orangutan species. These results suggest that the boosted interactional opportunities in captivity rather than mere differences in environmental affordances or communicative needs drive the wild-captive contrast in orangutan communicative repertoires. Overall, this fine-grained analysis of repertoires further underscores that not only a species’ social organisation but also the targeted audience may have a profound impact on communicative behaviour.
Significance statement
Navigating a dynamic social environment often requires flexible signal use. While it has repeatedly been shown that the social organisation and structure of species predict the complexity of their communication systems, the mechanisms underlying these relationships are largely unknown. Because targeted studies to assess this issue in great apes are difficult, we take an alternative approach here: we compare the same species living in the wild and in artificial habitats in captivity. This contrast allows a direct test of how repertoires respond to the relevant difference in socio-ecological conditions. Our results show that the diversity of interaction partners (i.e. social opportunities), but not the diversity of social goals (i.e. possible interaction outcomes) or the broader physical opportunities (i.e. safe ground use), predict the size and consistency of wild and captive signalling repertoires.
Studies of climate variation commonly rely on chemical and isotopic changes recorded in sequentially-produced growth layers, such as in corals, shells and tree rings, as well as in accretionary deposits—ice and sediment cores, and speleothems. Oxygen isotopic compositions (δ18O) of tooth enamel are a direct method of reconstructing environmental variation experienced by an individual animal. Here we utilize long-forming orangutan dentitions (Pongo spp.) to probe recent and ancient rainfall trends on a weekly basis over ∼ 3–11 years per individual. We first demonstrate the lack of any consistent isotopic enrichment effect during exclusive nursing, supporting the use of primate first molar teeth as environmental proxies. Comparisons of δ18O values (n = 2016) in six modern Bornean and Sumatran orangutans reveal a high degree of overlap, with more consistent annual and bimodal rainfall patterns in the Sumatran individuals. Comparisons with fossil orangutan δ18O values (n = 955) reveal similarities between modern and late Pleistocene fossil Sumatran individuals, but differences between modern and late Pleistocene/early Holocene Bornean orangutans. These suggest drier and more open environments with reduced monsoon intensity during this earlier period in northern Borneo, consistent with other Niah Caves studies and long-term speleothem δ18O records in the broader region. This approach can be extended to test hypotheses about the paleoenvironments that early humans encountered in southeast Asia.
Comparative analyses are the backbone of evolutionary analysis. However, their record in producing a consensus has not always been good. This is especially true of attempts to understand the factors responsible for the evolution of large brains, which have been embroiled in an increasingly polarised debate over the past three decades. We argue that most of these disputes arise from a number of conceptual errors and associated logical fallacies that are the result of a failure to adopt a biological systems-based approach to hypothesis-testing. We identify four principal classes of error: a failure to heed Tinbergen's Four Questions when testing biological hypotheses, misapplying Dobzhansky's Dictum when testing hypotheses of evolutionary adaptation, poorly chosen behavioural proxies for underlying hypotheses, and the use of inappropriate statistical methods. In the interests of progress, we urge a more careful and considered approach to comparative analyses, and the adoption of a broader, rather than a narrower, taxonomic perspective.
Tropical rain forests are represented in Angola by the narrow and fragmented southwards extension of the Guineo-Congolian rain forests of the Congo Basin and West Africa. This Chapter defines and characterises tropical rain forests, and compares the diversity of African forests with those of Central and South America and of South East Asia. The evolution and dynamics of African rain forests, and the role of human activity through the Holocene is discussed. Angola’s forest types are defined, their distribution, physical conditions, physiognomy and floristic and faunistic composition, plant-animal interactions, and forest gap-phase dynamics are detailed.
In recent years, computer science has made major advances in understanding drawing behavior. Artificial intelligence, and more precisely deep learning, has displayed unprecedented performance in the automatic recognition and classification of large databases of sketches and drawings collected through touchpad devices. Although deep learning can perform these tasks with high accuracy, the way they are performed by the algorithms remains largely unexplored. Improving the interpretability of deep neural networks is a very active research area, with promising recent advances in understanding human cognition. Deep learning thus offers a powerful framework to study drawing behavior and the underlying cognitive processes, particularly in children and non-human animals, on whom knowledge is incomplete. In this literature review, we first explore the history of deep learning as applied to the study of drawing along with the main discoveries in this area, while proposing open challenges. Second, multiple ideas are discussed to understand the inherent structure of deep learning models. A non-exhaustive list of drawing datasets relevant to deep learning approaches is further provided. Finally, the potential benefits of coupling deep learning with comparative cultural analyses are discussed.
The interface of sexual behavior and evolutionary psychology is a rapidly growing domain, rich in psychological theories and data as well as controversies and applications. With nearly eighty chapters by leading researchers from around the world, and combining theoretical and empirical perspectives, The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology is the most comprehensive and up-to-date reference work in the field. Providing a broad yet in-depth overview of the various evolutionary principles that influence all types of sexual behaviors, the handbook takes an inclusive approach that draws on a number of disciplines and covers nonhuman and human psychology. It is an essential resource for both established researchers and students in psychology, biology, anthropology, medicine, and criminology, among other fields. Volume 4: Controversies, Applications, and Nonhuman Primate Extensions addresses controversies and unresolved issues; applications to health, law, and pornography; and non-human primate evolved sexual psychology.
Orangutan females live semi-solitarily, spending 50–80 percent of their time alone, with only their dependent offspring for company (van Schaik, 1999). They are philopatric (Arora et al., 2012; van Noordwijk et al., 2002) and establish their home ranges in an area that overlaps with their natal range as well as with those of other females, both maternal relatives and nonrelatives (Ashbury et al., 2020; Morrogh-Bernard, 2009). Males disperse from their natal range as they become independent of their mother around the age of ten to twelve years (Nietlisbach et al., 2012) and settle far away from their natal area. Adult males are not territorial, and their home ranges overlap with those of females, but are far larger (Singleton et al., 2009). Determining male ranging patterns is challenging because their ranging area far exceeds the size of all study areas covered by earth-bound researchers, and individual males may not be around for several months or even years (Dunkel et al., 2013; Spillmann et al., 2017; Utami Atmoko et al., 2009a). In sum, orangutans have a dispersed social and mating system with high female site fidelity and widely roaming males.
Flies are implicated in carrying and mechanically transmitting many primate pathogens. We investigated how fly associations vary across six monkey species (Cercopithecus ascanius, Cercopithecus mitis, Colobus guereza, Lophocebus albigena, Papio anubis, and Piliocolobus tephrosceles) and whether monkey group size impacts fly densities. Fly densities were generally higher inside groups than outside them, and considering data from these primate species together revealed that larger groups harbored more flies. Within species, this pattern was strongest for colobine monkeys, and we speculate this might be due to their smaller home ranges, suggesting that movement patterns may influence fly-primate associations. Fly associations increase with group sizes and may thus represent a cost to sociality.
Objectives
Dietary diversity in primates is reflected in their dental morphology, with differences in size and shape of teeth. The objective of this study is to investigate the relationship between molar morphology and macrowear patterns in Pongo , Gorilla , and Pan to obtain dietary information.
Methods
We have examined 68 second lower molars using the Occlusal Fingerprint Analysis method including 18 chimpanzees, 28 gorillas, and 22 orangutans. We selected only molars from wildshot specimens characterized by a moderate degree of wear. High‐resolution digital models of teeth were created using a white scanning light system with a resolution of 45 μm.
Results
The macrowear patterns of Pan were significantly different from those of Gorilla and of Pongo , differences that are mostly due to shearing wear. Gorilla and Pongo macrowear patterns are dominated by phase II areas, followed by lingual phase I facets, while in Pan we observe a significant increase in buccal phase I facets. The latter group also displays the highest macrowear variation across the sample examined in this study.
Conclusions
The molar macrowear patterns of the great apes analyzed in this study did not confirm our initial hypothesis of finding larger crushing and grinding areas in Pongo and more shearing wear in Gorilla . Pan shows the most variable macrowear, which is probably associated with their more flexible diet. The similarity between Pongo and Gorilla macrowear patterns may be due to a larger intake of mechanically challenging foods that could obfuscate dietary wear signals generated by softer foods.
Some animal species have been presumed to be purely diurnal. Yet, they show flexibility in their activity rhythm, and can occasionally be active at night. Recently, it has been suggested that chimpanzees may rarely engage in nocturnal activities in savannah forests, in contrast to the frequent nocturnal feeding of crops observed at Sebitoli, Kibale National Park, Uganda. Here we thus aimed to explore the factors that might trigger such intense nocturnal activity (e.g. harsher weather conditions during daytime, low wild food availability or higher diurnal foraging risk) in this area. We used camera-traps set over 18 km ² operating for 15 months. We report activities and group composition from records obtained either within the forest or at the forest interface with maize fields, the unique crop consumed. Maize is an attractive and accessible food source, although actively guarded by farmers, particularly during daytime. Out of the 19 156 clips collected, 1808 recorded chimpanzees. Of these, night recordings accounted for 3.3% of forest location clips, compared to 41.8% in the maize fields. Most nocturnal clips were obtained after hot days, and most often during maize season for field clips. At night within the forest, chimpanzees were travelling around twilight hours, while when at the border of the fields they were foraging on crops mostly after twilight and in smaller parties. These results suggest that chimpanzees change their activity rhythm to access cultivated resources when human presence and surveillance is lower. This survey provides evidence of behavioral plasticity in chimpanzees in response to neighboring human farming activities, and emphasizes the urgent need to work with local communities to mitigate human-wildlife conflict related to crop-feeding.
The “cashew conundrum” is a seminal event in the history of economics. Professor Richard Thaler observed that his guests were happier not having the option to consume pre-dinner cashews. The fact that people can be happier with fewer options directly contradicts core assumptions in neoclassical economics, and is labeled an “anomaly” by behavioral economics. Far from being surprising, the cashew phenomenon is predicted by biological methods for understanding behavior. The cashew conundrum is not an anomaly, but rather an ordinary.
Efficiency leads to leisure
Humans are animals—merely another lineage of great apes. However, we have diverged in significant ways from our ape cousins and we are perennially interested in how this happened. Kraft et al . looked at energy intake and expenditure in modern hunter-gatherer societies and great apes. They found that we do not spend less energy while foraging or farming, but we do acquire more energy and at a faster rate than our ape cousins. This difference may have allowed our ancestors to spend more time in contexts that facilitated social learning and cultural development. —SNV
More than 800 isolated teeth of fossil Pongo have been recovered from cave sites in the vicinity of Chongzuo in Guangxi, southern China, ranging from the Early to Late Pleistocene (2.0–0.1 Ma). These collections provide a unique regional window into the evolutionary history of orangutans over a two-million-year period at the northernmost extent of their former geographic range. Here we investigate the nature and timing of the evolutionary change in the dental size of fossil orangutans from Chongzuo. Fossil tooth size (mesiodistal length∗buccolingual breadth) was compared against an extant Pongo pygmaeus standard (n = 106 individuals). During the course of the Pleistocene, orangutans from southern China exhibited a progressive reduction in overall dental size. Early Pleistocene Pongo has cheek teeth with occlusal areas that are 38.1% larger than those of extant P. pygmaeus. Those from the Middle and Late Pleistocene are 25.2% and 18.9% larger, respectively. Previously, the size difference in dentition between the Early to Middle Pleistocene and Middle to Late Pleistocene samples was used to differentiate time-successive species of Pongo, namely Pongo weidenreichi and Pongo devosi. However, with access to larger samples and better representation of populations through time, the evidence in support of this taxonomic arrangement requires reconsideration. Diminution of the teeth now appears to be a gradual evolutionary transformation rather than a punctuated event. Moreover, the morphological features that distinguish the Chongzuo fossil orangutans from extant Pongo spp. remain uniform throughout the Pleistocene. Retaining P. weidenreichi and P. devosi as anagenetic species remains an option, but, given the current evidence, we consider it preferable to assign all of the fossil orangutans from Chongzuo to P. weidenreichi. Beyond resolving questions of alpha taxonomy, the study of fossil orangutan dental size provides a basis for estimating body mass, which has implications for interpreting the paleobiology of Pleistocene Pongo in southern China.
This study analyses 749 drawings by five female Bornean orang-utans (Pongo pygmaeus) at Tama Zoological Park in Japan. We searched for differences between individuals but also tried to identify possible temporal changes among the drawings of one individual, Molly, who drew almost 1300 drawings from 2006 to 2011. An analysis of the drawings was carried out after collecting quantitative and qualitative variables. Our findings reveal evidence of differences in the drawing style of the five individuals as well as creative changes in Molly’s drawing style throughout her lifetime. Individuals differed in terms of the colours used, the space they filled, and the shapes (fan patterns, circles, or loops) they drew. Molly drew less and less as she grew older, and we found a significant difference between drawings produced in winter, when orang-utans were kept inside and had less activity, and those produced during other seasons. Our results suggest that the drawing behaviour of these five orang-utans is not random and that differences among individuals might reflect differences of styles, states of mind, and motivation to draw.
Sexual coercion is widespread in the animal kingdom. Its direct forms, including harassment and forced copulation, have largely been investigated as an expression of (alternative) male reproductive strategies, rather than the result of a sexual conflict between the sexes. Likewise, the frequent occurrence of forced copulations in orang-utans (Pongo spp.) has been attributed to male strategies and more recently also to concealed female fecundity. So far, however, the immediate contextual variables leading to forced copulations have rarely been examined. We compared two orang-utan populations, Suaq (Pongo abelii, Sumatra) and Tuanan (Pongo pygmaeus, Borneo), both characterized by an individual-based fission–fusion lifestyle, whereas their socioecology differs. We assessed how the occurrence of female-resisted and voluntary copulations was affected by female reproductive state, male morph (unflanged or flanged), measures of male–male competition, male–female relationship and ecological factors. Besides female reproductive state and male morph, predictors of female resistance were related to male–male competition. First, female resistance was more likely towards subordinate males who were displaced from proximity to the female by another male during that association. Second, the presence of additional flanged males increased the probability of female resistance. Third, the latency to both the arrival of another male and to the end of the association after sexual interactions was shorter if there was female resistance. We conclude that sexual coercion in orang-utans is highly dependent on the vicinity of more dominant males and can only be understood in the light of sexual conflict: While males force copulations when at risk of losing access to a female and thus follow a ‘now-or-never’ strategy, female resistance follows a ‘not-you-now’ pattern, which is ultimately consistent with an infanticide avoidance strategy.
Comparative studies on tool technologies in extant primates, especially in our closest living relatives, offer a window into the evolutionary foundations of tool use in hominins. Whereas chimpanzee tool technology is well studied across populations, the scarcity of described tool technology in wild populations of our other closest living relative, the bonobo, is a mystery. Here we provide a first report of the tool use repertoire of the Kokolopori bonobos and describe in detail the use of leaf-umbrellas during rainfall, with the aim to improve our knowledge of bonobo tool use capacity in the wild. The tool use repertoire of the Kokolopori bonobos was most similar to that of the nearby population of Wamba and comprised eight behaviors, none in a foraging context. Further, over a 6-month period we documented 44 instances of leaf-umbrella use by 22 individuals from three communities, suggesting that this behavior is habitual. Most leaf-umbrella tool users were adult females, and we observed a nonadult using a leaf-umbrella on only a single occasion. While the study and theory of tool technologies is often based on the use of tools in foraging tasks, tool use in bonobos typically occurs in nonforaging contexts across populations. Therefore, incorporating both foraging and nonforaging contexts into our theoretical framework is essential if we wish to advance our understanding of the evolutionary trajectories of tool technology in humans.
Whether nonhuman species can change their communicative repertoire in response to socio-ecological environments has critical implications for communicative innovativeness prior to the emergence of human language, with its unparalleled productivity. Here, we use a comparative sample of wild and zoo-housed orang-utans of two species (Pongo abelii, P. pygmaeus) to assess the effect of the wild-captive contrast on repertoires of gestures and facial expressions. We find that repertoires on both the individual and population level are larger in captive than wild settings, regardless of species, age class or sampling effort. In the more sociable Sumatran species, dominant use of signals towards single outcomes was also higher in captive settings. We thus conclude that orang-utans exposed to more sociable and terrestrial conditions evince behavioural plasticity, in that they produce additional innate or innovated signals that are highly functionally specific. These findings suggest a latent capacity for innovativeness in these apes’ communicative repertoires.
From early infancy, human face-to-face communication is multimodal, comprising a plethora of interlinked communicative and sensory modalities. Although there is also growing evidence for this in nonhuman primates, previous research rarely disentangled production from perception of signals. Consequently, the functions of integrating articulators (i.e. production organs involved in multicomponent acts) and sensory channels (i.e. modalities involved in multisensory acts) remain poorly understood. Here, we studied close-range social interactions within and beyond mother-infant pairs of Bornean and Sumatran orang-utans living in wild and captive settings, to examine use of and responses to multicomponent and multisensory communication. From the perspective of production, results showed that multicomponent acts were used more than the respective unicomponent acts when the presumed goal did not match the dominant outcome for a specific communicative act, and were more common among non-mother-infant dyads and Sumatran orang-utans. From the perception perspective, we found that multisensory acts were more effective than the respective unisensory acts, and were used more in wild compared to captive populations. We argue that multisensory acts primarily facilitate effectiveness, whereas multicomponent acts become relevant when interaction outcomes are less predictable. These different functions underscore the importance of distinguishing between production and perception in studies of communication. Fröhlich et al. present a study of orangutan social interaction within and beyond mother-offspring pairings wherein the composition of communicative acts is categorized by production and perception. They demonstrate that communicative acts can vary across research setting, species and social partner, with act composition affecting interaction outcomes.
Orangutans are an endemic to Indonesia and Malaysia with an almost extinct with critically endangered status and only found on the islands of Sumatra and Kalimantan/Borneo. Orangutan extinction is mainly threat by habitat loss and fragmentation as well as low reproduction rates. Habitat fragmentation, along with habitat loss, should be clearly considered when assessing implications of landscape change for population extinctions. Environmental changes force species to immediately adapt both behaviourally and physiologically. Forest structure affects the adaptability and nesting behaviour of orangutans. One of the steps to prevent orangutan extinction is by increasing habitat connectivity through corridors and reducing fragmentation of landscapes as well as stopping habitat lost.
Assessments of the welfare status of captive and semi-captive animals often compare how their expression of natural behaviors differs from that of free-ranging conspecifics. From December 2015–2016, we recorded and analyzed the activity budget and postural behaviors of three orangutans in Bukit Merah Orang Utan Island (BMOUI) to evaluate their welfare status. The orangutans’ activity budget was dominated by resting (60%), feeding (13%), playing (14%), and moving (9%). Behavioral categories followed a similar trend: resting > feeding > moving > playing, except that the subadult male spent significantly more time playing than the two adults. The most predominant posture was sitting (47.0%), followed by pronograde standing (29.4%), lying (10.5%), and clinging (4.5%). Our results suggest that orangutans on BMOUI engage in less feeding but more resting, and show less postural diversity than free-ranging individuals. We propose that appropriate interventions to shift activity budgets, especially feeding vs. resting, and postural behaviors of captive orangutans toward those found in free-ranging orangutans might be beneficial for their welfare and survival.
From foraging patterns in a single tree to social interactions across a home range, how primates use space is a key question in the field of primate behavioral ecology. Drawing on the latest advances in spatial analysis tools, this book offers practical guidance on applying geographic information systems (GIS) to central questions in primatology. An initial methodological section discusses niche modelling, home range analysis and agent-based modelling, with a focus on remote data collection. Research-based chapters demonstrate how ecologists apply this technology to a suite of topics including: calculating the intensity of use of both range and travel routes, assessing the impacts of logging, mining and hunting, and informing conservation strategies.
Katingan watershed is a one of bornean orangutan (Pongo pygmaeus wrumbii) habitat that currently Critically Endangered status, and protected by Indonesian government regulations (P.106/2018), that included in Appendix 1. The condition of the bornean orangutan habitat is increasingly threatened by land cover changes. Management habitat is needed to protect the populations of bornean orangutan. The aim of this research was to develop the spatial distribution model of bornean orangutan habitat as a reference to habitat management. Habitat suitability model of bornean orangutan develop by logistic regression and based on five environmental variables covering elevation, distance from cultural sites, distance from roads, distance from settlements, and NDVI. The Hosmer-Lemeshow test showing feasibility value was 0.481 with Nagelker R 2 =0.866, and Kappa Accuracy 77%. The total habitat suitability of bornean orangutan in the Katingan watershed was 1,250,174.35 ha (64.11% of the Katingan watershed area). The main habitat of bornean orangutan was identified in the National Park (TN), Protection Forest (HL), and Nature Reserve/Nature Conservation Area (KSA/KPA) with area 395,178.30 ha (31.66% of the total habitat area). Isolated habitat identified in the northeastern of the Katingan watershed. Habitat corridors can be created in forested areas with a minimum width of 500 meters.. How to cite (CSE Style 8 th Edition): Mustofa, Syartinilia, Arifin HS. 2020. Model spasial distribusi habitat orangutan kalimantan (Pongo pygmaeus wurmbii) menggunakan logistik regresi di DAS Katingan. JPSL 10(4): 627-638. http://dx.
Sexual coercion, in the form of forced copulations, is relatively frequently observed in orangutans and generally attributed to their semi-solitary lifestyle. High ecological costs of association for females may be responsible for this lifestyle and may have prevented the evolution of morphological fertility indicators (e.g., sexual swellings), which would attract (male) associates. Therefore, sexual conflict may arise not only about mating per se but also about associations, because males may benefit from associations with females to monitor their reproductive state and attempt to monopolize their sexual activities. Here, we evaluate association patterns and costs for females when associating with both males and females of two different orangutan species at two study sites: Suaq, Sumatra (Pongo abelii), and Tuanan, Borneo (Pongo pygmaeus wurmbii). Female association frequency with both males and females was higher in the Sumatran population, living in more productive habitat. Accordingly, we found that the cost of association, in terms of reduced feeding to moving ratio and increased time being active, is higher in the less sociable Bornean population. Males generally initiated and maintained such costly associations with females, and prolonged associations with males led to increased female fecal cortisol metabolite (FCM) levels at Tuanan, the Bornean population. We conclude that male-maintained associations are an expression of sexual conflict in orangutans, at least at Tuanan. For females, this cost of association may be responsible for the lack of sexual signaling, while needing to confuse paternity.
Significance statement
Socioecological theory predicts a trade-off between the benefits of sociality and the ecological costs of increased feeding competition. Orangutans’ semi-solitary lifestyle has been attributed to the combination of high association costs and low predation risk. Previous work revealed a positive correlation between association frequencies and habitat productivity, but did not measure the costs of association. In this comparative study, we show that females likely incur costs from involuntary, male-maintained associations, especially when they last for several days and particularly in the population characterized by lower association frequencies. Association maintenance therefore qualifies as another expression of sexual conflict in orangutans, and especially prolonged, male-maintained associations may qualify as an indirect form of sexual coercion.
Gorillas are one of our closest living relatives, the largest of all living primates, and teeter on the brink of extinction. These fascinating animals are the focus of this in-depth and comprehensive examination of gorilla biology. Gorilla Biology combines recent research in morphology, genetics and behavioural ecology to reveal the complexity and diversity of gorilla populations. The first section focuses on morphological and molecular variation and underscores the importance of understanding diverse biological patterns at all levels in testing evolutionary and adaptive hypotheses and elucidating subspecies and species diversification. Following are discussions of the ecological constraints that influence gorilla social organization and highlight their surprising flexibility. The book ends with discussions of the conservation status of gorillas and the many and increasing threats to their continued survival. Giving insight into the evolutionary biology of these unique primates, this book will be essential reading for primatologists, anthropologists and evolutionary biologists.
In Guangxi Zhuang Autonomous Region, southern China, Quaternary mammalian assemblages, commonly known as “Stegodon-Ailuropoda fauna”, are well documented in the central and southwest parts of the region. Unfortunately, our knowledge of Quaternary biogeographic variation in other areas of Guangxi is poor due to limited systematic investigations. Here, we report the faunal remains from the newly discovered Diaozhongyan (“DZY”) cave site in northeast Guangxi. Our initial excavation in autumn 2016 resulted in the removal of 10 square meters of sediment and the discovery of 304 pieces of large mammal teeth. Biostratigraphic correlations indicate a late Middle Pleistocene age and in situ fossil teeth and calcites were Uranium-series dated to ~210 ka. The DZY faunal assemblage consists of many typical components of the traditional “Ailuropoda-Stegodon” fauna representative of southern China. Interestingly, giant pandas, identified as Ailuropoda melanoleuca baconi, are one of the dominant components of the DZY fauna (15% of the entire assemblage). However, giant pandas rarely dominate Quaternary faunal assemblages in southern China. In addition, fossil orangutan (Pongo weidenreichi), one of the most common species in central and south Guangxi during the Middle Pleistocene, is absent in DZY in northeast Guangxi. Further, fossil orangutans have not been reported from other sites in Hunan or Hubei province. We hypothesize that the Nanling Mountains served as a geographic barrier for this species. Fossil orangutans are present southwest of this biogeographic line, but are absent northeast of the line. This biogeographic boundary needs to be further evaluated with additional studies.
The best estimates of dates of divergence of major, present day primate groups based on paleontological and anatomical evidence differ from explicit or implied dates based on biochemical data. In this paper the paleontological evidence for dating the hominoid lineages leading to the Hylobatidae (gibbons and siamangs) and to Gorilla and Homo is presented. The dates of divergence based on paleontological data differ from those based on biochemical data by at most a factor of five. The discrepancy between the sets of dates can therefore be resolved by variation by a factor of at most five in the rate of protein evolution. The biochemical technique used to estimate dates of divergence of taxonomic groups measures the similarity of molecules. it is phenetic rather than phyletic. As time since divergence increases, phenetic comparisons increasingly underestimate the total amount of evolution that has occurred since divergence. Phenetic approaches to sequence data do not detect parallel fixations, fixations of back mutations, or alternative routes of fixing amino acid substitutions. The frequency distribution of fixations per codon, when these are phenetically inferred, can be well described by means of a Poisson distribution if the zero fixation category is adjusted to an optimal value. This suggests that molecular evolutionary events are equally likely to occur, and that protein evolution should occur at a constant rate. The frequency distribution of phyletically inferred fixations per codon, however, cannot be well described by a single Poisson distribution, even when the zero fixation category is adjusted. This suggests, as does a considerable body of other data, that molecular evolutionary events are not equally likely, and that rates of evolution of proteins may be expected to vary. Estimated dates of divergence older than dates used to calibrate phenetically based estimates tend to be too young, while dates younger than calibration dates tend to be too old. Dates of divergence of primate groups based on phenetic comparisons, if corrected for this effect, conflict with the best documented part of the primate fossil record, the later Hominidae, not with the less well established parts. It therefore seems prudent to accept the best paleontological dates for divergence of major primate taxa rather than to question them on the basis of the biochemical data. Branching sequences determined on the basis of biochemical data appear to be relatively reliable, but even these must be considered with caution.
... there is one point which has delayed the right conception and understanding of the evolutionary process for a long time. This was the idea that the older the morphological age of the human form is, the more it must approach the living anthropoids. This conclusion did not take into account that the big apes, too, must have undergone essential changes during the same period of time in which man evolved. WEIDENREICH, Apes, Giants, and Man, Chicago, 1946, p. 11/12. CONTENTS Introduction . . . 175 Homo sapiens L. subsp . . . 182 Pongo pygmaeus palaeosumatrensis nov. subsp . . . 187 Incisors . . . 188 Canini . . . 199 Premolars . . . 208 Molars . . . 229 Milk dentition . . . 264 The prehistoric orang-utan population . . . 269 Pongo pygmaeus (Hoppius) subsp. from the Pleistocene of Java . . . 272 Pongo pygmaeus weidenreichi nov. subsp. from the Pleistocene of S. China . . . 280 Summary; the evolution of the dentition of Pongo pygmaeus (Hoppius) . . . 284 INTRODUCTION Man's natural interest in his nearest relatives has built up an enormous
Extending the observations of previous investigators on the presence or absence of sensitivy to P.T.C. in anthropoid apes and to Simians of lower groups, it has been possible to establish the proportions of tasters and of non-tasters in various genera. These frequencies present geographical variations which, at the moment, are difficult to explain. Experimental evidence is also presented to evaluate the threshold of sensitivity to this substance in eight specimens of chimpanzees.
