Orangutans (Pongo pygmaeus) Remember Old Acquaintances

Many social animals can discriminate between familiar and unfamiliar faces. Orangutans, however, lead a semi-solitary life and spend much of the day alone. As such, they may be less adept at recognizing conspecifics and are a good model for determining how social structure influences the evolution of social cognition such as facial recognition. The present study is the first report of whether orangutans can distinguish among individual faces. We adopted a preferential looking method and found that orangutans used facial discrimination to identify known conspecifics. This suggests that frequent and intense social interaction is not necessary for facial discrimination, although our findings were limited by the small number of stimuli and the unequal numbers of male and female orangutans depicted in the stimuli.     

Cooperative Problem Solving by Orangutans (Pongo pygmaeus)

A captive pair of subadult male orangutans (Pongo pygmaeus) performed a cooperative task without training. Both partners had to pull a handle simultaneously in order for each to get food. They also learned the importance of the partner at the apparatus to make a successful response. The requirements of the cooperative task appear to have been understood by the orangutans, much like chimpanzees (Pan troglodytes) in the same situation. In contrast, capuchins (Cebus apella) succeeded in the cooperative task with a limited understanding of the requirement of the task and without taking into account the partner's role. These results gives further support to the hypothesis of a proximity of cognitive processes between chimpanzees and orangutans (in contrast to monkeys) though orangutans have not been seen to hunt cooperatively in the wild.     

Patterns of Gazing in Orangutans (Pongo pygmaeus)

Eyes play an important role in communication amongst humans and animals. However, relatively little is known about specific differences in eye morphology amongst primates and how these features might be associated with social structure and direction of gaze. We present a detailed study of gazing and eye morphology—exposed sclera and surrounding features—in orangutans. We measured gazing in rehabilitating orangutans in two contexts: interspecific viewing of the experimenter (with video camera) and intraspecific gazing (between subjects). Our findings show that direct staring is avoided and social looking is limited to certain age/social categories: juveniles engage in more looking at other orangutans than do adults or infants. While orangutans use eye movements in social communication, they avoid the more prolonged mutual gaze that is characteristic of humans, and also apparent in chimpanzees and gorillas. Detailed frame-by-frame analysis of videotapes from field and zoo studies of orangutans revealed that they pay visual attention to both human observers and conspecifics by glancing sideways, with the head turned at an angle away from the subject being observed. Mutual gaze was extremely rare, and we have observed only two incidences of gaze following. Orangutans in captivity appear to use a more restricted pattern of gazes compared to free-living, rehabilitating ones, possibly suggesting the presence of a pathological condition (such as depression) in the captive subjects. Our findings have implications for further investigations of social communication and cognition in orangutans.     

Orangutans (Pongo pygmaeus) do not form expectations based on their partner's outcomes

Several primate species form expectations based on others' outcomes, responding negatively when their outcomes differ from their partners'. The function and evolutionary pathway of this behavior are unknown, in part because all of the species which have been tested thus far share traits related to a gregarious lifestyle, intelligence, and cooperativeness. Our goal was to test whether inequity is a homology among primates or a convergence by comparing one species known to show social comparisons, the chimpanzee, to another great ape which differs on several of these life history characteristics. Using a protocol identical to one used previously with chimpanzees, we tested whether orangutans, an intelligent but predominantly solitary species with few opportunities to cooperate, responded similarly. To allow for a strong comparison with chimpanzees (and other species), we used socially housed adults of both sexes, tested with members of their social group. Orangutans did not respond negatively to inequity, supporting previous findings and indicating that inequity responses in apes are likely a convergence based on either sociality or cooperative tendency. These results in such closely related species highlight the need for additional comparative studies to understand better the function and evolution of social behaviors.     

圈养婆罗洲猩猩部分血液参数值测定

采集6家动物园18只健康婆罗洲猩猩(Pongo pygmaeus)的24份血液样本,进行血液常规及生化参数检测。依据性别(雄性14份,雌性10份)和年龄(幼龄个体7份,亚成体6份,成体11份)对研究对象进行分组,分别统计不同组别样本的血液参数值,并进行组间比较。研究结果表明,雌、雄两组之间血液参数没有显著差异(One Way ANOVA test,P> 0.05)。淋巴细胞(LYM)比率随着年龄的增长而降低(One Way ANOVA test,F=5.200,P <0.05)。雄性成年个体血液中的谷丙转氨酶(ALT)浓度显著高于雌性个体(One Way ANOVA test,F=4.911,P <0.05),其他参数未呈现性别间差异(One Way ANOVA test,P> 0.05)。总蛋白(TP)呈现年龄组间的差异(One Way ANOVA test,F=4.715,P <0.05)。所检测圈养婆罗洲猩猩血液中葡萄糖含量较高,应在饲养过程中给予关注。     

Alkaptonuria in an orangutan (Pongo pygmaeus)

Alkaptonuria has been diagnosed in a laboratory born, five year old, female orangutan. In man, this relatively rare amino acid metabolic disorder is characterized by arthritis, pigmentation of cartilage, and darkening of the urine upon standing. The color change is due to oxidation of homogentisic acid not normally found in the urine. The condition in man is a simple Mendelian recessive trait characterized by the absence of homogentisic acid oxidase activity. At two years of age, the affected orangutan was noted to void urine of normal color, which upon standing turned a very dark maroon color. Clinically the animal appeared normal; and the results of a urinalysis, hemogram, and survey radiographs confirmed this evaluation. Nonspecific laboratory determinations used to diagnose alkaptonuria in man were positive. Homogentisic acid in the urine was confirmed by paper chromatography, and a quantitative evaluation was made by a commercial laboratory. The orangutan has shown no clinical change or evidence of ochronosis during the past three years, and quarterly survey radiographs show no evidence of osteoarthropathy. The affected orangutan has half brothers and sisters in the colony but no full sibling. Both parents are young, however, and are being paired in an attempt to produce siblings. It is hoped that additional animals with this metabolic defect will become available for use as potential models for studying this inborn error of metabolism.     

New tool use by wild Sumatran orangutans (Pongo pygmaeus abelii)

Two forms of tool use by wild Sumatran orangutans are reported from the Agusan Monitoring Station, a new research site in Indonesia. One form, a branch "hook" used in locomotion, has not been reported previously in wild orangutans. The second form, a leaf "pad" used to protect the hands and feet from thorns while feeding, shares similarities in form and function with a tool type used by orangutans at Ketambe, a nearby research site. Both instances of tool use occurred in areas of disturbance, and appear to be spontaneous inventions under novel conditions, although habitual use of the tool in other ecological contexts is plausible. A summary of the distribution of tool use types in wild orangutans is presented.     

Genetic Divergence of Orangutan Subspecies (Pongo pygmaeus)

Microsatellites and mitochondrial DNA sequences were studied for the two subspecies of orangutans (Pongo pygmaeus), which are located in Borneo (P. p. pygmaeus) and Sumatra (P. p. abelii), respectively. Both subspecies possess marked genetic diversity. Genetic subdivision was identified within the Sumatran orangutans. The genetic differentiation between the two subspecies is highly significant for ND5 region but not significant for 16s rRNA or microsatellite data by exact tests, although F _ST estimates are highly significant for these markers. Divergence time between the two subspecies is approximately 2.3 ± 0.5 million years ago (MYA) estimated from our data, much earlier than the isolation of their geological distribution. Neither subspecies underwent a recent bottleneck, though the Sumatran subspecies might have experienced expansion approximately 82,000 years ago. The estimated effective population sizes for both subspecies are on the order of 10⁴. Our results contribute additional information that may be interpreted in the context of orangutan conservation efforts. Received: 13 June 2000 / Accepted: 30 January 2000     

Hand preferences in captive orangutans (Pongo pygmaeus)

The strength of the evidence for population-level handedness in the great apes is a topic of considerable debate, yet there have been few studies of handedness in orangutans. We conducted a study of manual lateralization in a captive group of eight orangutans (Pongo pygmaeus) ranking the degrees of manual preference according to a defined framework. We analyzed five behavioral patterns: eat (one- and two-handed), make/modify tool, oral tool-use, and manual tool-use. Although some individuals showed significant manual preferences for one or more tasks, at the group-level both one-handed and two-handed eating, oral tool-use, and make/modify tool were ranked at level 1 (unlateralized). Manual tool-use was ranked at level 2, with four subjects demonstrating significant hand preferences, but no group-level bias to the right or left. Four subjects also showed hand specialization to the right or left across several tasks. These results are consistent with most previous studies of manual preference in orangutans. The emergence of manual lateralization in orangutans may relate to more complex manipulative tasks. We hypothesize that more challenging manual tasks elicit stronger hand preferences.     

Strongyloidiasis in an infant orangutan (Pongo pygmaeus)

Necropsy of a 15-month-old male orangutan (Pongo pygmaeus) showed multiple nodular elevations of the mucosa of the colon, petechial hemorrhages in both lungs, and mucosal ulcerations in the cecum, appendix, and proximal colon. Light microscopy revealed filariform larvae of Strongyloides in the lung, colon, and mesenteric lymph nodes. Rhabditiform larvae were also observed in sections of colon.     

Positional behavior of female bornean orangutans (Pongo pygmaeus)

Observational data were collected on the positional behavior of habituated adult female orangutans in the rain forest of the Kutai National Park, East Kalimantan, Indonesia. Results revealed the following about locomotion during travel: movement was concentrated in the understory and lower main canopy; and brachiation (without grasping by the feet) accounted for 11% of travel distance, quadrupedalism for 12%, vertical climbing for 18%, tree-swaying for 7%, and clambering for 51%. In climbing and clambering, the animal was orthograde and employed forelimb suspension with a mixture of hindlimb suspension and support. Thus suspension by the forelimbs occurred in at least 80% of travel. Locomotion in feeding trees resembled that during travel but with more climbing and less brachiation. Feeding was distributed more evenly among canopy levels than was travel, and use of postures (by time) included sitting 50%, suspension with the body vertical 11%, and suspension by hand and foot with the body horizontal 36%. The traditional explanation of the evolution of the distinctive hominoid postcranium stresses brachiation. More recently it has been proposed that climbing, broadly defined and partly equivalent to clambering in this study, is the most significant behavior selecting for morphology. The biomechanical similarity of brachiation and the orthograde clambering of orangutans precludes the present results from resolving the issue for the evolution of Pongo. The orangutan is by far the largest mammal that travels in forest canopy, and a consideration of the ways that its positional behavior solves problems posed by habitat structure, particularly the tapering of branches and gaps between trees, indicates that suspensory capacities have been essential in permitting the evolution and maintenance of its great body size.     

A coprological study of parasitism in orangutans (Pongo pygmaeus) in Indonesia

Fecal specimens from 89 orangutans (36 captive, 34 rehabilitant, and 19 wild) at different locations in Indonesia were examined. Strongyloides spp, Balantidium coli, and strongylid nematodes were the most common infestations detected. A syngamid nematode, Mammomonogamus sp, is reported for the first time in orangutans.     

A report of behavioral lateralization in an infant orang-utan (Pongo pygmaeus)

The limb used to perform seven common activities was recorded during weekly observations of an infant orang-utan. For five of these behaviors, preferences were found that remained consistent in their direction, although there were week to week fluctuations in magnitude. Most notably, a right hand preference was found for nonfood reaching and a right hindlimb preference appeared for initiating locomotion. Although initially, food reaching was predominantly with the right hand, a shift toward preferential left hand use occurred during the final weeks of the study. Additionally, a left hand preference appeared when the infant touched either its body or head.     

Sensorimotor cognition in young feral orangutans (Pongo pygmaeus)

The goal of this study was to describe object manipulation in wild orangutan infants and juveniles. Object manipulation is an important subsistence activity that also reflects cognitive functioning. Orangutans were studied in the field, at the Tanjung Puting Reserve, Kalimantan Tengah, Indonesia. Fourteen orangutans, grouped by age (infants 2.5 to 4.6 years; juveniles 5 to 8.5 years), were observed over a total of 555 hr and for an average of three full dawn-to-dusk “follows” each. Young orangutan’s manipulations were categorized along a hierarchy of complexity. The least complex manipulations were single sensorimotor actions such as grasping, mouthing, and waving. The most complex manipulations were combinations and coordinations of actions, such as experimentation with objects, tool use, and planning. Manipulative behavior occurred mainly when foraging, i.e. when obtaining and processing food items. Interestingly, complex behavior occurred most often when locomoting. The most complex object manipulations, however, occurred rarely. Infants and juveniles exhibited equivalent levels of complexity. Several aspects of this study point to the importance of social assistance provided by competent mothers for the development of young orangutans’ ability to locomote and to locate, obtain, and process food items. This study also highlights the cognitive abilities of young wild orangutans regarding tool use.     

Microsatellite DNA variation in Bornean orangutans (Pongo pygmaeus)

Orangutans (Pongo pygmaeus) on the islands of Borneo and Sumatra are considered two separate subspecies. However, the genetic relationships between isolated populations on Borneo are not clear. This study determined the extent of variation within the Bornean subspecies of orangutan, using microsatellite DNA analysis. Blood samples were collected from 96 individuals of known origin from East, West and Central Kalimantan. Human microsatellite primer pairs located at human map position D2S141, D4S431, D 11S925, D16S420 and D17S791 were suitable for use in primates. D4S431 appeared monomorphic for all orangutans. In three cases (D2S141 East and West and D16S420 West), a highly significant excess of homozygous allele frequencies was detected, but with other primer pairs no significant difference in allele frequencies occurred. We conclude that the divergence between the different populations on Borneo is less than the variation within the populations. There was also evidence that inbreeding occurred within the populations.     

Oral tool use by captive orangutans (Pongo pygmaeus)

Eight captive orangutans (Pongo pygmaeus) were given wooden blocks embedded with raisins and bamboo as raw material for tool making in a study of manual laterality. In about three quarters of the raisin extraction bouts, the orangutans held the tool in the lips or teeth rather than in their hands. Three adult males and 2 adult females showed extreme (> or =92%) preference for oral tool use, a subadult male and an adult female used oral tools about half the time, and 1 adult female preferred manual tool use. Most oral tool users made short tools (approx. 4-10 cm long) that were held in the lips and (probably) supported by the tongue. Preference for oral tool use does not correlate with body weight, age or sex, but it may be related to hand size or individual preference. This is the first report of customary oral tool use as the norm in captive orangutans; it resembles the behavioral patterns reported by van Schaik et al. and Fox et al. in nature.     

Health evaluation of free-ranging and semi-captive orangutans (Pongo pygmaeus pygmaeus) in Sabah,Malaysia

Baseline data on health of free-ranging wildlife is essential to evaluate impacts of habitat transformation and wildlife translocation, rehabilitation, and reintroduction programs. Health information on many species, especially great apes, is extremely limited. Between 1996 and 1998, 84 free-ranging orangutans captured for translocation, underwent a complete health evaluation. Analogous data were gathered from 60 semi-captive orangutans in Malaysia. Baseline hematology and serology; vitamin, mineral and pesticide levels; and results of health evaluations, including physical examination, provide a baseline for future monitoring. Free-ranging and semi-captive orangutans shared exposure to 11 of 47 viruses. The semi-captive orangutans had significantly higher prevalence of antibodies to adenovirus (P < 0.0005) and rota (SA 11) virus (P < 0.008). More free-ranging than semi-captive animals had antibodies to Japanese encephalitis virus (P < 0.08) and foamy virus (P = 0.05). Exposure to parainfluenza and langat viruses was detected exclusively in semi-captive animals and exposure to sinbis virus was only found in free-ranging orangutans. There was evidence of exposure to respiratory syncytial virus, coxsackie virus, dengue virus, and zika virus in both groups. Ebstein-Barr virus was ubiquitous in both groups. Prevalence of antibodies against mumps virus changed from 0% in 1996 to 45% in 1998. No antibodies were detected to many important zoonotic viral pathogens, including herpesvirus and hepatitis virus. Prevalence of Balantidium coli and Plasmodium pitheci infections and exposure to mycobacterium was higher in the semi-captive animals. Differences in exposure to pathogens between the groups may be due to environmental factors including differences in exposures to other species, habitat quality, nutritional status, and other potential stressors. Differences in health parameters between captive and free-ranging orangutans need to be considered when planning conservation areas, translocation procedures, and rehabilitation protocols. Because survival of the orangutan is linked to animal and ecosystem health, results of this study will assist wildlife conservation programs by providing baseline health information.