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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. In 2017, we observed the capture and consumption of a slow loris (Nycticebus borneanus) by an adult unflanged male Bornean orangutan at Tuanan Orangutan Research Station, which is located in the Kapuas region of Central Kalimantan. The unflanged male was together with an adult female and her 3.5-year-old offspring throughout the event. However, despite the mother and her offspring watching the male closely and occasionally begging while he consumed the loris, he resisted all food-taking attempts. This study reports, to the best of our knowledge, the first documented case of slow loris predation and consumption by a Bornean orangutan, and thus provides an important data point for understanding primate predation on other primate species. [ABSTRACT FROM AUTHOR]

Chimpanzees and orangutans are able to generate innovative behaviors to solve complicated physical problems. For example, when presented with an out-of-reach peanut at the bottom of a vertical tube (floating peanut task—FPT), some of them spontaneously spit water into the tube until the peanut floats to the top. Yet, it is unclear whether this innovative solution results from repeating those actions that bring the peanut incrementally closer to the top or from anticipating the solution before acting. In the current study, we addressed this question by presenting three naïve orangutans with an opaque version of the FPT that prevented them from obtaining visual information about the effect of their actions on the position of the peanut. One of the subjects solved the opaque FPT in the very first trial: he collected water from the faucet and poured it into the opaque tube repeatedly until the hitherto non-visible peanut reached the top. This provides evidence for the first time that orangutans can potentially solve the FPT without relying on sensorimotor learning, but to some extent by mentally representing the problem. [ABSTRACT FROM AUTHOR]

Immature orangutans acquire their feeding skills over several years, via social and independent learning. So far, it has remained uninvestigated to what extent orangutan mothers are actively involved in this learning process. From a fitness point of view, it may be adaptive for mothers to facilitate their offspring's skill acquisition to make them reach nutritional independence faster. Food solicitations are potential means to social learning which, because of their interactive nature, allow to investigate the degree of active involvement of the mother. To investigate the role of food solicitation and the role of the mother in immatures' foraging skill acquisition, we analysed 1390 food solicitation events between 21 immature Sumatran orangutans (Pongo abelii) and their mothers, collected over 13 years at the Suaq Balimbing orangutan population. We found that solicitation rates decreased with increasing age of the immatures and increased with increasing processing complexity of the food item. Mothers were more likely to share complex items and showed the highest likelihoods of sharing around the age at which immatures are learning most of their feeding skills. Our results indicate that immature Sumatran orangutans use food solicitation to acquire feeding skills. Furthermore, mothers flexibly adjust their behaviour in a way that likely facilitates their offspring's skill acquisition. We conclude that orangutan mothers have a more active role in the skill acquisition of their offspring than previously thought. [ABSTRACT FROM AUTHOR]

A syndrome of chronic upper and lower airway disease leading to increased morbidity and mortality occurs primarily in captive orangutans. Similarities in symptoms to the inherited human respiratory disease, cystic fibrosis, led us to hypothesize that orangutan respiratory disease is a result of variants in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. We identified the nonsense variant, c.484A>T (p.Lys162X), in heterozygosity in an unaffected orangutan. Analysis of the pedigree of this orangutan confirmed that both his sire and deceased fetus also harbored the c.484A>T allele. An expression minigene harboring c.484A>T produced no full‐length CFTR protein in HEK293 cells. Finally, the c.484A>T CFTR messenger RNA abundance was severely reduced in primary nasal epithelial cells of the orangutan indicating that c.484A>T (p.Lys162X) is potentially lethal. Genetic screening of the captive orangutan population could be used to prevent transmission of this potentially lethal variant, and thus aid in the conservation of this critically endangered species. Research Highlights: Chronic respiratory disease is an important cause of mortality in captive orangutans; variants in the cystic fibrosis gene could be one cause. We identified the nonsense variant, c.484A>T (p.Lys162X), in heterozygosity in an orangutan. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This work presents the mapping of the traveling salesperson problem (TSP) based in pseudo-Boolean constraints to a graph of the D-Wave Systems Inc. We first formulate the problem as a set of constraints represented in propositional logic and then resort to the SATyrus approach to convert the set of constraints to an energy minimization problem. Next, we transform the formulation to a quadratic unconstrained binary optimization problem (QUBO) and solve the problem using different approaches: (a) classical QUBO using simulated annealing in a von Neumann machine, (b) QUBO in a simulated quantum environment, (c) QUBO using the D-Wave quantum machine. Moreover, we study the amount of time and execution time reduction we can achieve by exploring approximate solutions using the three approaches. Results show that for every graph size tested with the number of nodes less than or equal to 7, we can always obtain at least one optimal solution. In addition, the D-Wave machine can find optimal solutions more often than its classical counterpart for the same number of iterations and number of repetitions. Execution times, however, can be some orders of magnitude higher than the classical or simulated approaches for small graphs. For a higher number of nodes, the average execution time to find the first optimal solution in the quantum machine is 26% ( n = 6 ) and 47% ( n = 7 ) better than the classical. [ABSTRACT FROM AUTHOR]

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To protect Tapanuli orangutan it is essential to understand the actual situation. It has been studied 15% of its population live outside the protected area facing a density disruption due to forest conversion. Several best management practices have been created and tested for different natural concession types. Yet, the main objective to reduce the impact and increase wildlife survival is far away from the goal. To improve our understanding of the species survival within ongoing project construction, we conducted population density monitoring prior- to post-construction time frames within the hydroelectric dam project. Also, we carried out spatial analysis to understand the land cover change and orangutan’s suitable habitat distribution. This study found that during high construction activities, orangutans were avoiding the threat sources, and returned when the disturbances reduced. These findings indicated orangutans are ecology flexible and have the capability to increase its survival, although the company’s involvement is crucial to facilitate the successes. Our study is based on indirect observation, and spatial modeling, which may lead to an uncertain conclusion. Further research on orangutan ecology and behavior is prioritized.

Orangutan (Pongo spp.) fossils have been found throughout much of Pleistocene Southeast Asia. Today, Pongo is restricted to three living species on the islands of Borneo and Sumatra. They are predominately frugivores, and during fruit masting events their diets can consist entirely of fruit. However, food procurement strategies between masting events differ between islands and thus species. Sumatran orangutans (Pongo abelii) are largely able to fall back on non-masting fruit species, such as figs, such that they can maintain higher quality diets compared to their Bornean counterparts (Pongo pygmaeus), who ingest more lower quality and tougher foods between masting events. However, diets of fossil orangutans remain largely unknown. We investigated the diets of Sumatran orangutans from the Pleistocene deposits of the Padang Highlands, western Sumatra, using dental microwear texture analysis. We tested whether the diets of the fossil species were similar to those of Bornean orangutans, all great apes generally, and macaques that occupy similar habitats to modern orangutans, in order to gain insights into palaeoenvironments present in western Sumatra. We found that fossil orangutans consumed foods less tough than modern Bornean Pongo pygmaeus , and thus presumably more fleshy fruits (absent of significant seed mastication). We found no differences in the amount of hard object feeding between modern and fossil orangutans. Taken together, we suggest that Pleistocene orangutans from western Sumatra had similar diets to Pongo abelii, indicating that masting events were not a significant contributing factor in their intake of fruit. Finally, we suggest anisotropy values in orangutan dental microwear may be an important marker for fruit masting events in the Pleistocene. [ABSTRACT FROM AUTHOR]

In an era of mass extinction, who gets a life jacket, who is left to drown or swim—and on what basis? This article addresses these questions by analyzing how tropes and practices of responsibility are variously enacted, reworked, contested, and refused across the global nexus of orangutan conservation. Drawing on multisited, collaborative ethnography, we trace the mutually constitutive relation between multiple orangutan figures and commons imaginaries at different nodes of conservation—from environmental activism in the Global North to NGO‐villager encounters in rural Borneo. In so doing, we "uncommon" international conservation's encompassing planetary imaginaries, showing how dominant portrayals of the orangutan as a global responsibility are translated and fragmented in different settings. We further contemplate what an analytic of responsibility might bring to ongoing discussions about the "commoning" planetary epoch in which conservation is increasingly embedded: the Anthropocene. [commons, uncommoning, responsibility, orangutan conservation, the Anthropocene, Borneo, Indonesia] [ABSTRACT FROM AUTHOR]

African apes engage in a distinct form of locomotion called knuckle‐walking, but there is much ambiguity as to when and how this locomotor behavior evolved. This study aims to elucidate potential differences in knuckle‐walking elbow posture and loading in African apes through the study of trabecular bone. Using a whole‐epiphysis approach, we quantified variation in the trabecular structure of the distal humerus of chimpanzees, western lowland gorillas, and mountain gorillas in comparison to orang‐utans, siamangs, and a sample of Old and New World monkeys. Results demonstrate differences in the distribution of trabecular bone within the distal humerus that are consistent across taxa that habitually use a flexed‐elbow posture in comparison to those that use an extended elbow during locomotion. Western lowland gorillas show an extended‐elbow pattern consistent with the straight forelimb position during knuckle‐walking, whereas chimpanzees show a flexed‐elbow pattern. Unexpectedly, mountain gorillas show an intermediate pattern between their western counterparts and chimpanzees. The differences found in elbow joint posture between chimpanzees and gorillas, and between gorilla species, point to diversification in the knuckle‐walking biomechanical strategies among African apes, which has implications in the debate regarding the locomotor behavior from which human bipedalism arose. [ABSTRACT FROM AUTHOR]

Estimating stable isotopic offset values is crucial for dietary reconstructions. Although research into stable isotope ecology of wild nonhuman primates is increasing overall, only a minority of studies involve laboratory experiments. This study is the first to report the carbon and nitrogen stable isotopic offset values in hair and feces of orangutans. During an experiment lasting 1 week, the weight of each consumed food item was recorded for each of six captive Bornean orangutan (Pongo pygmaeus) individuals. The food, hair, and fecal samples were collected for a few days, and their stable carbon and nitrogen isotope ratios were measured using an elemental analyzer/isotope ratio mass spectrometer. Subsamples of feces were treated with ethanol during the preservation process. Monte Carlo analyses showed that the 95% confidence intervals (CIs) of the carbon and nitrogen offset values between hair and diet were +0.9‰ to +3.9‰ and +2.3‰ to +4.5‰, respectively. The 95% CIs of the carbon and nitrogen offset values between feces and diet were −3.7‰ to −0.9‰ and +0.3‰ to +2.7‰, respectively. The effect of ethanol treatment on the stable isotope ratios of feces was unclear and inconclusive. The computed offset values of hair in captive orangutans are similar to those reported in other nonhuman primates, although those of feces showed greater interspecies variations. The offset values estimated in this study contribute to isotopic studies into the feeding ecology of free-ranging orangutans who are critically endangered in most wild settings. [ABSTRACT FROM AUTHOR]

Investigating the morphological differences of the calcaneus in humans and great apes is crucial for reconstructing locomotor repertories of fossil hominins. However, morphological variations in the calcaneus of the great apes (chimpanzees, gorillas, and orangutans) have not been sufficiently studied. This study aims to clarify variations in calcaneal morphology among great apes based on three-dimensional geometric morphometrics. A total of 556 landmarks and semilandmarks were placed on the calcaneal surface to calculate the principal components of shape variations among specimens. Clear interspecific differences in calcaneal morphology were extracted, corresponding to the degree of arboreality of the three species. The most arboreal orangutans possessed comparatively more slender calcaneal tuberosity and deeper pivot region of the cuboid articular surface than chimpanzees and gorillas. However, the most terrestrial gorillas exhibited longer lever arm of the triceps surae muscle, larger peroneal trochlea, more concave plantar surface, more inverted calcaneal tuberosity, more everted cuboid articular surface, and more prominent plantar process than the orangutans and chimpanzees. These interspecific differences possibly reflect the functional adaptation of the calcaneus to locomotor behavior in great apes. Such information might be useful for inferring foot functions and reconstructing the locomotion of fossil hominoids and hominids. [ABSTRACT FROM AUTHOR]

Context: Agricultural expansion is a leading cause of deforestation and habitat fragmentation globally. Policies that support biodiversity and facilitate species movement across farmland are therefore central to sustainability efforts and wildlife conservation in these human-modified landscapes. Objectives: We investigated the conservation impact of several potential management scenarios on animal populations and movement in a human-modified tropical landscape, focusing on the critically endangered Bornean orangutan, Pongo pygmaeus. Methods: We used an individual-based modelling platform to simulate population dynamics and movements across four possible landscape management scenarios for a highly modified oil palm-dominated landscape in Sabah, Malaysian Borneo. Results: Scenarios that maximised the retention of natural forest remnants in agricultural areas through sustainability certification standards supported stable orangutan populations. These populations were up to 45% larger than those supported under development-focused scenarios, where forest retention was not prioritised. The forest remnants served as corridors or stepping-stones, increasing annual emigration rates across the landscape, and reducing orangutan mortality by up to 11%. Sensitivity analyses demonstrated that this outcome was highly contingent on minimising mortality during dispersal. Conclusions: Management that promotes maximising natural forest cover through certification, such as that promoted by the Roundtable on Sustainable Palm Oil, can maintain viable orangutan populations over the lifespan of an oil palm plantation and facilitate movement among otherwise isolated populations. However, minimising hunting and negative human–orangutan interactions, while promoting peaceful co-existence between apes and people, will be imperative to insure positive conservation outcomes. [ABSTRACT FROM AUTHOR]

Nut‐cracking with hammer tools (henceforth: nut‐cracking) has been argued to be one of the most complex tool‐use behaviors observed in nonhuman animals. So far, only chimpanzees, capuchins, and macaques have been observed using tools to crack nuts in the wild (Boesch and Boesch, 1990; Gumert et al., 2009; Mannu and Ottoni, 2009). However, the learning mechanisms behind this behavior, and the extent of nut‐cracking in other primate species are still unknown. The aim of this study was two‐fold. First, we investigated whether another great ape species would develop nut‐cracking when provided with all the tools and appropriate conditions to do so. Second, we examined the mechanisms behind the emergence of nut‐cracking by testing a naïve sample. Orangutans (Pongo abelii and Pongo pygmaeus) have the second most extensive tool‐use repertoire among the great apes (after chimpanzees) and show flexible problem‐solving capacities. Orangutans have not been observed cracking nuts in the wild, however, perhaps because their arboreal habits provide limited opportunities for nut‐cracking. Therefore, orangutans are a valid candidate species for the investigation of the development of this behavior. Four nut‐cracking‐naïve orangutans at Leipzig zoo (P. abelii; Mage = 16; age range = 10–19; 4F; at the time of testing) were provided with nuts and hammers but were not demonstrated the nut‐cracking behavioral form. Additionally, we report data from a previously unpublished study by one of the authors (Martina Funk) with eight orangutans housed at Zürich zoo (six P. abelii and two P. pygmaeus; Mage = 14; age range = 2–30; 5F; at the time of testing) that followed a similar testing paradigm. Out of the twelve orangutans tested, at least four individuals, one from Leipzig (P. abelii) and three from Zürich (P. abelii and P. pygmaeus), spontaneously expressed nut‐cracking using wooden hammers. These results demonstrate that nut‐cracking can emerge in orangutans through individual learning and certain types of non‐copying social learning. Research highlights: Nut‐cracking with a tool by wild chimpanzees has been argued to be one of the most complex non‐human animal tool‐use behaviors.To test the extent of this behavior in other great apes, and the learning mechanisms underlying it, 12 naïve orangutans (Pongo abelii and P. pygmaeus) across two testing institutions (Leipzig zoo and Zürich zoo) were provided with the materials of nut‐cracking (hammer tool and shelled nuts) but no demonstrations.At least four of the naïve orangutans spontaneously cracked nuts with the hammer tools, demonstrating a similar behavior to wild primate nut‐cracking.These findings suggest that orangutans can acquire nut‐cracking with hammer tools via a combination of individual learning and non‐copying social learning. [ABSTRACT FROM AUTHOR]

Orangutans (Pongo spp.) populations used to be widely distributed throughout Southeast Asia, from Java in the south to the Southern China in the north during the Pleistocene. Their populations have declined up to 75% of their original size and are now distributed only in parts of the tropical rainforests of Borneo and Sumatra. Pongo pygmaeus, Pongo tapanuliensis and Pongo abelii are the three most representative species, in this study, here we discussed the latter. Sumatran forests are generally suffering from deforestation with rates ranging from 3.74% to 49.85% between 2000 and 2012. Thus, human wildlife conflict intensity has escalated and gained more traction. Orangutans are known as arboreal great apes and need to build nests for resting. We applied the transect line method (three transects; each 1,000 m long) at different elevations in Soraya Research Station, Gelombang Village, Sultan Daulat sub-district, Subulussalam district, and assessed the nest characteristics. The characteristics are: (1) nesting position referring to the position of nest on a tree; (2) nest successional stages defining the age and leaf decay used in constructing a nest indicated with I (new) until V (almost gone); and (3) nest density to predict the density of nest per square km. Afterwards, the identified nesting trees along the transect were further identified based on their species, and assessed based on three characteristics (the tree height, diameter and the height of a nest measured from the soil). A total of 27 nests were found, and 44% were located in transect III or at the riparian. Out of 27, four orangutans' nests were found on Moraceae (Streblus elongatus) and Myrtaceae (Syzigium spp.), while three nests were found on Dipterocarpus sp. The tree height, tree diameter and nest height were 10 m--25 m (mean = 17.5 m; SD = ± 0.25), 10 cm--30 cm (mean = 20 cm; SD = ± 0.4) and 16 m-0 m (mean = 18 m; SD = ± 0.35), respectively. Meanwhile, nest density calculated based on the form: d = [N/ (L* 2w)], and the values obtained were 8.4, 13.45, 26.9 nests/km² located on transect I, II and III or at the riparian. The most commonly found nest successional stages and position were stage III and position 3, respectively. This study could serve as a baseline research in primate conservation and nest characterisation could be used as guidance for any future activity planning (e.g. tree reforestation) in a particular region and the existence of various tree species diversity are indispensable for maintaining orangutan habitats' quality. [ABSTRACT FROM AUTHOR]

The Sebangau National Park is a major stronghold for Bornean Orangutan (Pongo pygmaeus wurmbii) ranging from 6000 - 9000 individuals. In comparison with Bornean Orangutans, very little ecological fieldwork has been conducted to investigate sun bear biology, and there have been no thorough surveys of distribution or population densities. Thus, this study aimed to investigate the basic information on niche overlap between these two endangered species, specifically to quantify their relationship within the small-scale habitat in Punggualas area, SNP. Data was collected and measured during 15 - 21 June 2019; using line transects methods. A total of 6580 m was walked along 8 consecutive transects. Bear and aging sign follow Augeri protocols. A total 18 printed mark-claw and 17 Orangutan nests was measured according to the mentioned methodology. The relationships between signs use binary logistic regressions (StatPlus for Mac) and PCA model (using R), while interspecific relationships use Co-Occurrence modeling, ESP for Windows. The results showed that there is no difference between bear sign and orangutan nest (2: 26.249; df :1, p-value: 0.001); While the results on habitat selection between transects is failed to reject the null hypothesis (2 = 0.29; df :1, p-value: 0.490). The Mann-Whitney U test, also confirmed no distinctive overlap between the Orangutan and the Sun Bear (Z: 0.84; p-value: 0.40). The co-occurrence simulations also revealed significant results (C-Score = 1.00), by means both target animals co-existed in the habitat. Obviously, the Orangutan and Sun Bear occupy the same habitat. There is no distinctive overlap between them in terms of tree species selection and having a close interrelationship in terms of feeding ground, whereas the fruiting is not available. The only distinctive difference is that the Bear sign was tend hindering waterlogged terrain. [ABSTRACT FROM AUTHOR]

Understanding of animal responses to dynamic resource landscapes is based largely on research on temperate species with small body sizes and fast life histories. We studied a large, tropical mammal with an extremely slow life history, the Western Bornean orangutan (Pongo pygmaeus wurmbii), across a heterogeneous natural landscape encompassing seven distinct forest types. Our goals were to characterize fluctuations in abundance, test hypotheses regarding the relationship between dispersion dynamics and resource availability, and evaluate how movement patterns are influenced by abiotic conditions. We surveyed abundance in Gunung Palung National Park, West Kalimantan, Indonesia, for 99 consecutive months and simultaneously recorded weather data and assessed fruit availability. We developed a Bayesian hierarchical distance sampling model to estimate population dispersion and assess the roles of fruit availability, rainfall, and temperature in driving movement patterns across this heterogeneous landscape. Orangutan abundance varied dramatically over space and time. Each forest type was important in sustaining more than 40% of the total orangutans on site during at least one month, as animals moved to track asynchronies in fruiting phenology. We conclude that landscape-level movements buffer orangutans against fruit scarcity, peat swamps are crucial fallback habitats, and orangutans' use of high elevation forests is strongly dependent on abiotic conditions. Our results show that orangutans can periodically occupy putative-sink habitats and be virtually absent for extended periods from habitats that are vitally important in sustaining their population, highlighting the need for long-term studies and potential risks in interpreting occurrence or abundance measures as indicators of habitat importance. [ABSTRACT FROM AUTHOR]

This study was aimed to determine the eating habits of Faunus (F.) ater based on gastric contents analysis to determine the type of food that F. ater likes and to determine the eating habits of F. ater based on the length class, carried out in the Bale and Reuleung rivers. Sampling was carried out once and 150 samples of F. ater were examined. The data obtained were analyzed for variance followed by Duncan's double-spaced test at 5% level to determine the eating habits of F. ater. The types of food found in the digestive tract were identified by matching the picture with the book. The results of the analysis of gastric contents from 150 samples of F. ater found 3 types of food, namely Amphisolenia sp., Parafavella sp. and Nannochloropsis sp. The frequencies of Parafavella sp. and Nannochloropsis sp. recorded in the F. ater hull of the two rivers showed no significant difference, namely 12.9% for Krueng Bale:13.1% for Krueng Reuleung and 87.1% for Krueng Bale and 86.86% for Krueng Reuleung. Analysis of the F. ater length class on the food occurrence frequency index showed that there were 8 F. ater length classes for the two rivers observed. In general, at each length of food class F. ater was dominated by Nannochloropsis sp. and Paravafella sp. The results of the analysis of gastric contents in 300 samples of F. ater in Krueng Bale and Reuleung found three types of food, namely Amphisolenia sp., Parafavella sp. and Nannochloropsis sp. The percentage value of the frequency of eating occurrences of F. ater showed Nannochloropsis sp. the highest compared to other types of food, while the lowest frequency of eating was Amphisolenia sp. There are eight length classes of F. ater class for the two rivers observed. In conclusion, at each length of food class F. ater was dominated by Nannochloropsis sp. and Paravafella sp. [ABSTRACT FROM AUTHOR]

I have spent over 40 years studying the behavior of our closest living relatives, the apes. In this paper, I review my research on the spacing, mating, and vocal behavior of gibbons and orangutans (Pongo pygmaeus) and the vocal and social behavior of chimpanzees (Pan troglodytes). I devote special attention to results derived from a 25‐year‐long study of a remarkable and extraordinarily large group of chimpanzees that has recently fissioned at Ngogo in Kibale National Park, Uganda. I conclude with some advice for the next generation of field primatologists. Research Highlights: I review the results of my field research on gibbons, orangutans, and chimpanzees.My findings provide insights into the spacing, mating, and vocal behavior of gibbons and orangutans and the vocal and social behavior of chimpanzees. [ABSTRACT FROM AUTHOR]

Polyspecific associations, in which individuals of multiple species move together, have not been reported in Asian primates. However, only one study in India has shown this lack of association quantitatively. We collected data on interspecific encounters among 5 species of diurnal primates in Danum Valley by censusing 4 predetermined routes of 9.9 km, covering 1544.3 km, and tracking red leaf monkeys (Presbytis rubicunda) for 423 h over 25 mo. We tested the null hypothesis that the frequency and duration of encounters did not differ from chance levels. During censuses, we detected primates 373 times and found 2 species on the same 100-m segment only 6 times. This frequency was not significantly different from the chance level. While following red leaf monkeys, the frequency of encounters was lower than expected by chance with Müeller's gibbons (Hylobates muelleri) but higher than expected by chance with Bornean orangutans (Pongo pygmaeus) in the nonfruiting season. Interspecific encounters accounted for 6.4% of tracking time, and the encounter duration was significantly longer than expected by chance for orangutans. Red leaf monkeys did not change their rate or direction of travel on meeting another species. We could not distinguish the association between red leaf monkeys and orangutans in the nonfruiting season from the possibility that the two species were independently attracted to the same place. In conclusion, we show the absence of active and consistent polyspecific association and identify avoidance in some species pairs in an Asian primate community. [ABSTRACT FROM AUTHOR]

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. We analyzed 15 years of detailed observational data on social learning, associations, and diet repertoires of 50 immatures (16 females and 34 males), from 2 orangutan populations. Specific to the feeding context, we found sex differences in the development of social interest: Throughout the dependency period, immature females direct most of their social attention at their mothers, whereas immature males show an increasing attentional preference for individuals other than their mothers. When attending to non-mother individuals, males show a significant bias toward immigrant individuals and a trend for a bias toward adult males. In contrast, females preferentially attend to neighboring residents. Accordingly, by the end of the dependency period, immature females show a larger dietary overlap with their mothers than do immature males. These results suggest that immature orangutans show attentional biases through which they learn from individuals with the most relevant ecological knowledge. Diversifying their skills and knowledge likely helps males when they move to a new area. In sum, our findings underline the importance of fine-grained social inputs for the acquisition of ecological knowledge and skills in orangutans and likely in other apes as well. To understand the development and evolution of cognition of our closest relatives, we need to investigate their learning behavior during every-day life. This study finds that wild orangutan males and females differ in their social learning strategies and subsequent learning outcomes from an early age, underlining the general importance of, and the effects of sex on, social learning in non-human great apes. [ABSTRACT FROM AUTHOR]

Pronounced temporal and spatial variation in the availability of food resources can produce energetic deficits in organisms. Fruit-dependent Bornean orangutans face extreme variation in fruit availability and experience negative energy and protein balance during episodes of fruit scarcity. We evaluate the possibility that orangutans of different sexes and ages catabolize muscle tissue when the availability of fruit is low. We assess variation in muscle mass by examining the relationship between urinary creatinine and specific gravity and use the residuals as a non-invasive measure of estimated lean body mass (ELBM). Despite orangutans having a suite of adaptations to buffer them from fruit scarcity and associated caloric deficits, ELBM was lower during low fruit periods in all age-sex classes. As predicted, adult male orangutans had higher ELBM than adult females and immatures. Contrary to expectation, flanged and unflanged males did not differ significantly in ELBM. These findings highlight the precarity of orangutan health in the face of rapid environmental change and add to a growing body of evidence that orangutans are characterized by unique metabolic traits shaped by their unpredictable forest environment. [ABSTRACT FROM AUTHOR]

A 13-year-old Bornean orangutan diagnosed with life threatening Streptococcus pyogenes broncho-pneumonia was kept in a state of deep sedation for 20 days via continuous intra-venous (IV) infusion of zolazepam -tiletamine and IV haloperidol to allow consistent IV administration of ceftazidime and gatifloxacine. The use of long-term deep sedation allowed carrying out a particularly demanding treatment not generally associated with zoological patients. The treatment was ultimately successful. [ABSTRACT FROM AUTHOR]

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. Furthermore, adult orangutans show sex-specific dispersal and activity patterns. This study investigates sex differences in adult foraging behavior and sheds light on how these differences develop in immatures. We analyzed 11 years of feeding data on ten adult female, seven flanged male, and 14 immature Bornean orangutans (Pongo pygmaeus wurmbii) at Tuanan in Central Kalimantan, Indonesia. We found that the diets of the adult females were significantly broader and required more processing steps before ingestion than the diets of flanged males. We also found evidence for a similar difference in overall diet repertoire sizes. For the immatures, we found that whereas females reached 100% of their mothers' diet spectrum size by the age of weaning, males reached only around 80%. From the age of 4 years on (i.e., years before being weaned) females had significantly broader daily diets than males. We found no difference in daily or overall diet processing intensity of immature males and females but found preliminary evidence that immature males included fewer items of their mother's diet in their own diets that were processing-intensive. Overall, our results suggest that by eating a broader variety and more complex to process food items, female orangutans go to greater lengths to achieve a balanced diet than males do. These behavioral differences are not just apparent in adult foraging behavior but also reflected in immature development from an early age on. Significance Statement: In many species, males and females have different nutritional needs and are thus expected to show sex-specific foraging behavior. Sex differences in several aspects of foraging behavior have been found in various species, but it remains largely unclear when and how those develop during ontogeny, which is especially relevant for long-lived altricial species that learn foraging skills over many years. In our study, we analyzed a cross-sectional and longitudinal data set containing more than 750,000 feeding events of adult and immature Bornean orangutans (Pongo pygmaeus wurmbii). We found that adult females had significantly broader and more complex diets than males. We also found that these differences started to develop during infancy, suggesting that immature orangutans prepare for their sex-specific foraging niches long before those become physiologically relevant while they are still in constant association with their mothers and before being frequently exposed to other role models. [ABSTRACT FROM AUTHOR]

Coagulum in the semen of some primates plays different roles, depending on the species. In the present study, we examined sperm motility in the coagulum and liquid portions of semen collected from captive individuals from two great ape species: two adult Bornean orangutans (Pongo pygmaeus) (n = 27) and three adult chimpanzees (Pan troglodytes) (n = 14). The results revealed that orangutan sperm remained motile for significantly longer in the coagulum than in the liquid portion (> 18 h). By contrast, chimpanzee sperm motility did not differ significantly over time between the two portions of the semen, although motility was slightly higher in the liquid portion than in the coagulum. The evolution of the seminal coagulum is thought to be related to postcopulatory sperm competition; however, functions of seminal coagulum have not been completely elucidated. Our data from the orangutan semen suggest that in this species, seminal coagulum may strengthen own-sperm survival. This report is the first to provide evidence for this distinctive function of the seminal coagulum. This unique property of orangutan seminal coagulum might be attributable to their reproductive traits, e.g., difficulty in predicting ovulation due to a lack of genital swelling during estrus. The orangutan is a Critically Endangered species, and captive breeding, including artificial insemination (AI), is expected. However, worldwide, only one case of orangutan AI has been successful. Our findings may contribute to an understanding of their basic semen characteristics and help improve the AI method. [ABSTRACT FROM AUTHOR]

Decision outcomes in unpredictable environments may not have exact known probabilities. Yet the predictability level of outcomes matters in decisions, and animals, including humans, generally avoid ambiguous options. Managing ambiguity may be more challenging and requires stronger cognitive skills than decision-making under risk, where decisions involve known probabilities. Here we compare decision-making in capuchins, macaques, orangutans, gorillas, chimpanzees and bonobos in risky and ambiguous contexts. Subjects were shown lotteries (a tray of potential rewards, some large, some small) and could gamble a medium-sized food item to obtain one of the displayed rewards. The odds of winning and losing varied and were accessible in the risky context (all rewards were visible) or partially available in the ambiguous context (some rewards were covered). In the latter case, the level of information varied from fully ambiguous (individuals could not guess what was under the covers) to predictable (individuals could guess). None of the species avoided gambling in ambiguous lotteries and gambling rates were high if at least two large rewards were visible. Capuchins and bonobos ignored the covered items and gorillas and macaques took the presence of potential rewards into account, but only chimpanzees and orangutans could consistently build correct expectations about the size of the covered rewards. Chimpanzees and orangutans combined decision rules according to the number of large visible rewards and the level of predictability, a process resembling conditional probabilities assessment in humans. Despite a low sample size, this is the first evidence in non-human primates that a combination of several rules can underlie choices made in an unpredictable environment. Our finding that non-human primates can deal with the uncertainty of an outcome when exchanging one food item for another is a key element to the understanding of the evolutionary origins of economic behaviour. [ABSTRACT FROM AUTHOR]

The West has promoted for centuries a fragmentary and erroneous vision of the African continent, a territory subjected and enslaved by some of the great world powers. Colonialism helped foster a racist vision of Africa and its population from very early on, which was reflected in some animated short films made at the beginning of the 20th century. They did so by giving an archetypal vision of the African, both when they drew him as a human being --Jungle Jitters (Friz Freleng, 1938), The Isle of Pingo Pongo (Tex Avery, 1938)-- and when they did it by providing him with features of a jungle animal --Africa Squeaks (Bob Clampett, 1940), Congo Jazz (Hugh Harman y Rudolf Ising, 1930)--, to increase the feeling of inferiority to which all these regions were reduced. [ABSTRACT FROM AUTHOR]

This article draws on two research projects – one on orangutan conservation, and the other on religious change among indigenous Bidayuh communities – to reflect on the relations, technologies and processes involved in producing witnesses and witness-able truths. I compare two forms of witnessing: visualizations of environmental crisis and orangutan extinction, and modes of encountering invisible entities among Bidayuhs. Both involve the challenge of making the unseen visible or apprehensible and thus addressable. But whereas the first entails a crisis-laden visual imaginary that turns witnessing into a form of human stewardship over the environment, the second involves a more relational encounter involving mutual adjustment and responsivity to obligations and commitments. I suggest that this latter mode of witnessing invites us to reimagine both the crisis logic of environmental visualizations and ideals and practices of anthropological witnessing. [ABSTRACT FROM AUTHOR]

When presented with the option of either an immediate benefit or a larger, later reward, we may behave impatiently by choosing instant gratification. Nonetheless, when we can make the same decision ahead of time and plan for the future, we tend to make more patient choices. Here, we explored whether great apes share this core feature of human decision-making, often referred to as dynamic inconsistency. We found that orangutans, bonobos, and gorillas tended to act impatiently and with considerable variability between individuals when choosing between an immediate reward and a larger-later reward, which is a commonly employed testing method in the field. However, with the inclusion of a front-end delay for both alternatives, their decisions became more patient and homogeneous. These results show that great apes are dynamically inconsistent. They also suggest that, when choosing between future outcomes, they are more patient than previously reported. We advocate for the inclusion of diverse time ranges in comparative research, especially considering the intertwinement of intertemporal choices and future-oriented behavior., (© 2024. The Author(s).)

This article applies object detection to CCTV video material to investigate the potential of using machine learning to automate behavior tracking. This study includes video tapings of two captive Bornean orangutans and their behavior. From a 2 min training video containing the selected behaviors, 334 images were extracted and labeled using Rectlabel. The labeled training material was used to construct an object detection model using Create ML. The use of object detection was shown to have potential for automating tracking, especially of locomotion, whilst filtering out false positives. Potential improvements regarding this tool are addressed, and future implementation should take these into consideration. These improvements include using adequately diverse training material and limiting iterations to avoid overfitting the model.

In human infants, exploratory object manipulation is a major vehicle for cognitive stimulation as well as an important way to learn about objects and basic physical concepts in general. The development of human infants’ exploratory object manipulation follows distinct developmental patterns. So far, the degree of evolutionary continuity of this developmental process remains unclear. We investigated the development of exploratory object manipulations in wild orangutans. Our data included 3200 exploration events collected on 13 immatures between the ages of 0.5 and 13 years, at the Suaq Balimbing monitoring station in Indonesia. Our results identify several parallels between the development of exploratory behaviour in humans and orangutans: on top of a highly similar overall age trajectory, we found an increase in variability of the actions used, an increase in the number of body parts involved in each event, and an overall decrease of mouthing of the objects. All in all, our results show that orangutans progress through a developmental sequence of different aspects of exploration behaviour. In combination with previous findings from captivity, our results also provide evidence that exploratory object manipulations reflect cognitive development and might function as a means of cognitive stimulation not just in humans but across the great apes.

Abstract Background Some wild animals have been recognized as potential reservoirs of Leishmania infantum infection (e.g. carnivores, lagomorphs, rodents, etc.). Leishmania infantum was also identified infecting humans and lagomorphs (i.e. hares and rabbits) over the period of 2009–2016, with the latter acting as the main reservoirs involved in the human leishmaniosis outbreak in Madrid. Results Two cases of clinical leishmaniosis are reported in orangutans (Pongo pygmaeus pygmaeus) housed at two different centres in Madrid. The first is the case of a 36-year-old male orangutan with severe weight loss and apathy. A complete blood count and biochemical profile revealed anaemia, neutropenia, hypoalbuminaemia and elevated transaminases. Hepato-splenomegaly was also observed. Four months later, due to worsening of clinical signs (mainly bilateral epistaxis), blood and bone marrow samples were collected. Amastigotes of L. infantum were detected in macrophages from a bone marrow aspirate and by specific polymerase chain reaction. The second case was a 34-year-old female orangutan with severe weight loss and apathy and no other apparent clinical signs. A complete blood count and biochemical profile revealed anaemia, pancytopenia and hypoalbuminaemia. Splenomegaly and pericardial effusion were also observed. As leishmaniosis was included in the differential diagnosis, both blood and bone marrow samples were collected. Leishmania infantum infection was confirmed by microscopy, molecular diagnosis and serology (immunofluorescence antibody test). Both animals were treated daily with oral miltefosine for 28 days; allopurinol was also given uninterruptedly in Case 2 for at least 6 months. During follow-up, though good clinical recovery was clear, a lack of parasitological cure was confirmed molecularly in both blood and bone marrow samples from the two orangutans. In both habitats, the presence of the sand fly vector identified as Phlebotomus perniciosus was confirmed. Conclusions To our knowledge, this is the first report of L. infantum infection in great apes and in the endangered species P. p. pygmaeus. We are presently looking for L. infantum in other non-human primates living in the same peri-urban areas. If detected, we will examine the impacts of this serious disease on these critically endangered species.

Objectives: We aimed to investigate molar enamel development in fossil orangutans from Guangxi and shed light on the evolution of Asian great apes. Materials and methods: We collected 32 fossil orangutan molars, most of which were from Guangxi apothecaries and the Guangxi Daxin Heidong cave, and prepared histological sections of each molar. We then characterized aspects of dental development, including long period line periodicity, number of Retzius lines and lateral enamel formation time, cuspal enamel thickness, and enamel formation time. Results: The long period line periodicity in fossil orangutans ranged from 9 to 10 days (mean, 9.09 days). The molar lateral enamel formation time ranged from 1.48 to 3.17 years (540–1,152 days). Cuspal enamel thickness in fossil orangutan molars ranged from 949 to 2,535 μm, and cuspal enamel formation time ranged from 0.64 to 1.87 years. Molar enamel formation time of fossil orangutans ranged from 2.47 to 4.67 years. Discussion Long‐period line periodicity of fossil orangutans from Guangxi was within the variation range of extant orangutans, and the average long period line periodicity (9.09 days) of fossil orangutans from Guangxi in this study was lower than the values for extant orangutans (9.5 days) and fossil orangutans (10.9 days) from Sumatra and Vietnam. Orangutan enamel thickness may have gradually decreased from the Middle Pleistocene to Holocene. Crown formation time of fossil orangutans was slightly longer than that of extant orangutans, and the M1 emergence age of fossil orangutans from Guangxi was about 4–6 years. These findings might indicate the regional difference or evolutionary changes in orangutans since Pleistocene. Dental development of the Guangxi fossil orangutans were more similar to that of Asian Miocene apes, suggesting the closer evolutionary relationship of orangutans to Miocene Asian fossil apes. [ABSTRACT FROM AUTHOR]

Wildlife surveys were conducted in Usun Apau National Park (UANP), Sarawak from Oct 2017 to Oct 2020. This was the first attempt to document fauna diversity in Usun Apau National Park on the UANP plateau at 1200-1400 m a.s.l. On 17 September 2020, 10 AM, we observed an orangutan individual, Pongo pygmaeus, over a period of one minute at Libut Camp UANP (E: 114039'.546, N: 2052'36.44) at 1,020 m a.s.l. We also recorded four nests and orangutan vocalisation twice. This observation is important for Bornean orangutan conservation as this was the first orangutan sighting in UANP and well outside the species distribution range for in Sarawak. [ABSTRACT FROM AUTHOR]

The Tapanuli Orangutan (Pongo tapanuliensis) is the most threatened great ape species in the world. It is restricted to an area of about 1,000 km2 of upland forest where fewer than 800 animals survive in three declining subpopulations. Through a historical ecology approach involving analysis of newspaper, journals, books and museum records from the early 1800s to 2009, we demonstrate that historically Pongo tapanuliensis inhabited a much larger area, and occurred across a much wider range of habitat types and at lower elevations than now. Its current Extent of Occurrence is 2.5% and 5.0% of the historical range in the 1890s and 1940s respectively. A combination of historical fragmentation of forest habitats, mostly for small-scale agriculture, and unsustainable hunting likely drove various populations to the south, east and west of the current population to extinction. This happened prior to the industrial-scale forest conversion that started in the 1970s. Our findings indicate how sensitive P. tapanuliensis is to the combined effects of habitat fragmentation and unsustainable take-off rates. Saving this species will require prevention of any further fragmentation and killings or other removal of animals from the remaining population. Without concerted action to achieve this, the remaining populations of P. tapanuliensis are doomed to become extinct within several orangutan generations. [ABSTRACT FROM AUTHOR]

Piscine Molitor Patel, Japanese ship aboard a family of a child named Pi, to go to Canada, the storm eventually sinking into the ocean. Those who succeeded in riding on a ship on the ship were a hyena with Pi, a broken zebra, a rat, a Bengal tiger called Richard Parker, and an orangutan that would join them later. Pi gives the survival struggle, which lasts for days in a small boat in the middle of the ocean. Pi enters a tough life struggle against Richard Parker, along with the natural conditions. The film "Life of Pi" carries this miraculous survival struggle that Pi, who is in search of a creator since his childhood, has embarked on the screen, has a characteristic that can be evaluated from different perspectives. We will also try to evaluate the film in terms of sociology of religion, in particular messages to prove the existence of God. [ABSTRACT FROM AUTHOR]