Play Behavior Varies with Age, Sex, and Socioecological Context in Wild, Immature Orangutans ( spp.).

Unlabelled: Play is thought to serve different purposes at different times during ontogeny. The nature and frequency of play are expected to change accordingly over the developmental trajectory and with socio-ecological context. Orangutans offer the opportunity to disentangle the ontogenetic trajectories of solitary and social play with their extended immature phase, and socio-ecological variation among populations and species.

Orangutan males make increased use of social learning opportunities, when resource availability is high.

Humans' colonization of diverse habitats relied on our ancestors' abilities to innovate and share innovations with others. While ecological impacts on innovations are well studied, their effect on social learning remains poorly understood. We examined how food availability affects social learning in migrant orangutan unflanged males, who may learn from local orangutans through peering (i.

Wild and captive immature orangutans differ in their non-vocal communication with others, but not with their mothers.

Abstract: 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.

Reproductive success of Bornean orangutan males: scattered in time but clustered in space.

Abstract: The social and mating systems of orangutans, one of our closest relatives, remain poorly understood. Orangutans ( spp) are highly sexually dimorphic and females are philopatric and maintain individual, but overlapping home ranges, whereas males disperse, are non-territorial and wide-ranging, and show bimaturism, with many years between reaching sexual maturity and attaining full secondary sexual characteristics (including cheek pads (flanges) and emitting long calls). We report on 21 assigned paternities, among 35 flanged and 15 unflanged, genotyped male Bornean orangutans (), studied from 2003 to 2018 in Tuanan (Central Kalimantan, Indonesia).

Alternative reproductive tactics of unflanged and flanged male orangutans revisited.

In many slowly developing mammal species, males reach sexual maturity well before they develop secondary sexual characteristics. Sexually mature male orangutans have exceptionally long periods of developmental arrest. The two male morphs have been associated with behavioral alternative reproductive tactics, but this interpretation is based on cross-sectional analyses predominantly of Northwest Sumatran populations.

Individual variation and plasticity in the infant-directed communication of orang-utan mothers.

Between-individual variation in behavioural expression, such as social responsiveness, has been shown to have important eco-evolutionary consequences. However, most comparative research on non-human primate communication has focused on species- or population-level variation, while among- and within-individual variation has been largely ignored or considered as noise. Here, we apply a behavioural reaction norm framework to repeated observations of mother-offspring interactions in wild and zoo-housed orang-utans () to tease apart variation on the individual level from population-level and species-level differences.

Orangutans have larger gestural repertoires in captivity than in the wild-A case of weak innovation?

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 orangutans of two species () 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 levels are larger in captive than in wild settings, regardless of species, age class, or sampling effort.

Slow loris (Nycticebus borneanus) consumption by a wild Bornean orangutan (Pongo pygmaeus wurmbii).

Vertebrate predation and consumption by wild Bornean orangutans (Pongo pygmaeus spp.) is rare. In contrast to recorded observations of slow loris consumption by Sumatran orangutans (Pongo abelii), no cases of this have been previously published for Bornean orangutans in the wild.

The development and maintenance of sex differences in dietary breadth and complexity in Bornean orangutans.

Abstract: Orangutans show a pronounced sexual dimorphism, with flanged males (i.e., males with fully grown secondary sexual characteristics) reaching twice the size of adult females.

Multicomponent and multisensory communicative acts in orang-utans may serve different functions.

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.

Immature wild orangutans acquire relevant ecological knowledge through sex-specific attentional biases during social learning.

As a part of growing up, immature orangutans must acquire vast repertoires of skills and knowledge, a process that takes several years of observational social learning and subsequent practice. Adult female and male orangutans show behavioral differences including sex-specific foraging patterns and male-biased dispersal. We investigated how these differing life trajectories affect social interest and emerging ecological knowledge in immatures.

The cost of associating with males for Bornean and Sumatran female orangutans: a hidden form of sexual conflict?

Abstract: 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.

The slow ape: High infant survival and long interbirth intervals in wild orangutans.

Orangutans (Pongo spp.) are reported to have extremely slow life histories, including the longest average interbirth intervals of all mammals. Such slow life history can be viable only when unavoidable mortality is kept low.

Correction to: development of foraging skills in two orangutan populations: needing to learn or needing to grow?

[This corrects the article DOI: 10.1186/s12983-016-0178-5.].

Nutritional ecology of wild Bornean orangutans (Pongo pygmaeus wurmbii) in a peat swamp habitat: Effects of age, sex, and season.

Unlabelled: The spatial and temporal variation in food abundance has strong effects on wildlife feeding and nutrition. This variation is exemplified by the peatland forests of Central Kalimantan, which are characterized by unpredictable fruiting fluctuations, relatively low levels of fruit availability, and low fruit periods (<3% of trees fruiting) that can last nearly a year. Challenged by these environments, large, arboreal frugivores like orangutans must periodically rely on non-preferred, lower-quality foods to meet their nutritional needs.

Development of foraging skills in two orangutan populations: needing to learn or needing to grow?

Background: Orangutans have one of the slowest-paced life histories of all mammals. Whereas life-history theory suggests that the time to reach adulthood is constrained by the time needed to reach adult body size, the needing-to-learn hypothesis instead suggests that it is limited by the time needed to acquire adult-level skills. To test between these two hypotheses, we compared the development of foraging skills and growth trajectories of immature wild orangutans in two populations: at Tuanan (), Borneo, and Suaq Balimbing (), Sumatra.

Postdispersal nepotism in male long-tailed macaques (Macaca fascicularis).

Cooperative behaviors are promoted by kin selection if the costs to the actor are smaller than the fitness benefits to the recipient, weighted by the coefficient of relatedness. In primates, cooperation occurs primarily among female dyads. Due to male dispersal before sexual maturity in many primate species, however, it is unknown whether there are sufficient opportunities for selective tolerance and occasional coalitionary support for kin selection to favor male nepotistic support.

Nutritional Differences between Two Orangutan Habitats: Implications for Population Density.

Bottom-up regulatory factors have been proposed to exert a strong influence on mammalian population density. Studies relating habitat quality to population density have typically made comparisons among distant species or communities without considering variation in food quality among localities. We compared dietary nutritional quality of two Bornean orangutan populations with differing population densities in peatland habitats, Tuanan and Sabangau, separated by 63 km.

Why do orangutans leave the trees? Terrestrial behavior among wild Bornean orangutans (Pongo pygmaeus wurmbii) at Tuanan, Central Kalimantan.

Orangutans (genus Pongo) are the largest arboreal mammals, but Bornean orangutans (P. pygmaeus spp.) also spend time on the ground.

Endocrinological correlates of male bimaturism in wild Bornean orangutans.

Among primates, orangutans are unique in having pronounced male bimaturism leading to two fully adult morphs that differ in both physical appearance and behavior. While unflanged males have a female-like appearance, flanged males have the full suite of secondary sexual characteristics, including cheek flanges and a large throat sac. So far, hormonal correlates of arrested development in unflanged males and the expression of secondary sexual characteristics in flanged males have only been studied in zoo-housed individuals.

The Ontogeny of Gap Crossing Behaviour in Bornean Orangutans (Pongo pygmaeus wurmbii).

For orangutans, the largest predominantly arboreal primates, discontinuous canopy presents a particular challenge. The shortest gaps between trees lie between thin peripheral branches, which offer the least stability to large animals. The affordances of the forest canopy experienced by orangutans of different ages however, must vary substantially as adult males are an order of magnitude larger in size than infants during the early stages of locomotor independence.

Validation of an acoustic location system to monitor Bornean orangutan (Pongo pygmaeus wurmbii) long calls.

The long call is an important vocal communication signal in the widely dispersed, semi-solitary orangutan. Long calls affect individuals' ranging behavior and mediate social relationships and regulate encounters between dispersed individuals in a dense rainforest. The aim of this study was to test the utility of an Acoustic Location System (ALS) for recording and triangulating the loud calls of free-living primates.

The evolution of the patterning of human lactation: a comparative perspective.

Some four decades ago, Jeanne Altmann started her detailed field studies of baboon mothers and their infants with a focus on the behavioral ecology of maternal reproductive investment. Around the same time, Sarah Hrdy studied langur mothers and their infants, focusing on the influence of the social environment on a female's reproductive options and decisions. Their pioneering work has inspired many subsequent studies of female primate reproduction in its natural context and shaped our own work on primate mothers.

Variation in developmental arrest among male orangutans: a comparison between a Sumatran and a Bornean population.

Introduction: The presence of two sexually active male morphs with different reproductive tactics in a single species is rare among mammals. The most striking case of bimaturism among primates is exhibited by the orangutan (Pongo spp), in which one adult morph, the unflanged male, irreversibly develops into another one, the flanged form, but may remain arrested in the unflanged state for many years. However, it has been suggested that such arrest is less common among Bornean orangutans (Pongo pygmaeus) compared to Sumatrans (Pongo abelii).