Wild Bornean orangutan (Pongo pygmaeus wurmbii) feeding rates and the Marginal Value Theorem

The Marginal Value Theorem (MVT) is an integral supplement to Optimal Foraging Theory (OFT) as it seeks to explain an animal's decision of when to leave a patch when food is still available. MVT predicts that a forager capable of depleting a patch, in a habitat where food is patchily distributed, will leave the patch when the intake rate within it decreases to the average intake rate for the habitat. MVT relies on the critical assumption that the feeding rate in the patch will decrease over time. We tested this assumption using feeding data from a population of wild Bornean orangutans (Pongo pygmaeus wurmbii) from Gunung Palung National Park. We hypothesized that the feeding rate within orangutan food patches would decrease over time. Data included feeding bouts from continuous focal follows between 2014 and 2016. We recorded the average feeding rate over each tertile of the bout, as well as the first, midpoint, and last feeding rates collected. We did not find evidence of a decrease between first and last feeding rates (Linear Mixed Effects Model, n = 63), between a mid-point and last rate (Linear Mixed Effects Model, n = 63), between the tertiles (Linear Mixed Effects Model, n = 63), nor a decrease in feeding rate overall (Linear Mixed Effects Model, n = 146). These findings, thus, do not support the MVT assumption of decreased patch feeding rates over time in this large generalist frugivore.     

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

Primates - 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...     

Airsacculitis in fourteen juvenile southern Bornean orangutans (Pongo pygmaeus wurmbii)

BACKGROUND: Airsacculitis is a clinical condition which has been reported in a range of primates species, including orangutans. METHODS: This report describes the occurence and management of airsacculitis in fourteen juvenile Southern Bornean orangutans (Pongo pygmaeus wurmbii) that presented beween January 1st 1999 and January 31st 2001 at the Orangutan Care Center and Quarantine (OCC&Q), Kalimantan Tengah, Indonesia (S 2 degrees 43' 49.2"; E 111 degrees 38' 54.2"). Details of the signalment, clinical history, presenting clinical signs, clinicopathological findings and bacterial isolates in each case were reviewed. RESULTS: Cough, halitosis and nasal discharge were the most frequently observed clinical signs. A range of Gram-negative bacteria were isolated from infected air sacs, including Pseudomonas sp., Enterobacter sp. and Klebsiella pneumoniae. A simple drainage and lavage technique was used in cases where surgical intervention was indicated, in combination with local and systemic antibiotic therapy. CONCLUSIONS: The importance of early diagnosis, prompt management and antibiotic selection, based on bacterial culture and sensitivity profiles, is outlined.     

Perineal repair of a full‐thickness rectal prolapse in a wild Sumatran orangutan (Pongo abelii)

A Delorme's procedure perineal surgical repair was performed in a wild adult male Sumatran orangutan (Pongo abelii) with a chronic persistent rectal prolapse that had been unsuccessfully treated by 6 previous surgeries. The rectal prolapse did not recur, and the orangutan was successfully released to the wild, 6 weeks later.     

Fatality of a wild Bornean orangutan (Pongo pygmaeus morio): behavior and death of a wounded juvenile in Danum Valley, North Borneo

Reports of wild great ape fatalities have been very limited, and only two have described wild orangutan deaths. We found a wounded juvenile female Bornean orangutan on 7 October 2006 in the Danum Valley, Sabah, Malaysia, and observed the individual's behavior for 7 days until her death on 13 October 2006. The 5-6-year-old orangutan, which we had observed since 2004, was wounded in the left brachium, back, and right hand. The individual's behavior changed after injury; the mean nest-nest active time became significantly shorter than before injury (from 12 h 3 min to 9 h 33 min), the mean waking time became significantly later (0552-0629 hours) and the mean bedtime became significantly earlier (from 1747 to 1603 hours). In the activity budget, resting increased significantly from 28.0 to 53.3%. Traveling and feeding decreased significantly from 23.5 to 12.7% and from 45.6 to 32.8%, respectively. The rate of brachiation during traveling and nest making decreased, whereas ground activity increased from 0 to 9%. We observed one vomiting incident and four occurrences of watery diarrhea during the 7 days before the individual died. The results of an autopsy performed by a local veterinarian suggested that the cause of death was septicemia because of Pseudomonas aeruginosa infection of the severely contaminated wounds. The morphology and distribution of the wounds suggested they had been incurred during an attack by a large animal with fangs and/or claws. This juvenile female became independent of its mother at ~4-5 years of age, slightly earlier than average. This individual might have been vulnerable to predatory attack because of her small body size (~5 kg at death) and lack of the mother's protection.     

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.     

Philopatry and reproductive success in Bornean orang-utans (Pongo pygmaeus)

Behavioural observations suggest that orang-utans are semi-solitary animals with females being philopatric and males roaming more widely in search of receptive partners, leading to the prediction that females are more closely related than males at any given site. In contrast, our study presents evidence for male and female philopatry in the orang-utan. We examined patterns of relatedness and parentage in a wild orang-utan population in Borneo using noninvasively collected DNA samples from animals observed to defecate, and microsatellite markers to assess dispersal and mating strategies. Surprisingly, resident females were equally as related to other resident females (mean r(xy) = 0.303) as resident males were to other resident males (mean r(xy) = 0.305). Moreover, resident females were more related to each other and to the resident males than they were to nonresident females, and resident males were more related to each other (and resident females) than they were to nonresident males. We assigned genetic mothers to 12 individuals in the population, while sires could be identified for eight. Both flanged males and unflanged males achieved paternity, similar to findings reported for Sumatran orang-utans.     

Diverticulitis with rupture and fatal peritonitis in a Sumatran orangutan (Pongo pygmaeus)

A 30-year-old male Sumatran orangutan (Pongo pygmaeus) presented with signs of depression, lethargy, anorexia, and diarrhea that progressed to acute colic. Exploratory laparotomy revealed fibrinopurulent peritonitis and 50 cm of devitalized small intestine. The surgically resected small intestine contained several mucosal diverticula along the mesenteric attachment; one had ruptured, resulting in peritonitis. Fifteen days after surgery, the orangutan's abdominal incision dehisced. Repeated laparotomy revealed dehiscence of the distal intestinal anastomosis site, as well as extensive adhesions and purulent exudate. The defect was repaired, and the abdomen was extensively irrigated and closed, but the animal died within 24 hours. To our knowledge, this is the first report of diverticulitis in a great ape. Diverticulosis should be considered in the differential diagnosis for great apes that present with signs of depression, lethargy, anorexia, and/or diarrhea.     

Comparative analysis of sperm motility in liquid and seminal coagulum portions between Bornean orangutan (Pongo pygmaeus) and chimpanzee (Pan troglodytes)

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.

     

A resurgence in reproductive behavior in a previously inactive male orangutan (Pongo pygmaeus abelii)

A male orangutan, who had sired one offspring in 1973, displayed no sexual activity over a period of years despite the continuing presence of his mate. Reproductive behavior recurred after (1) relocation to a new environment, (2) an apparent reduction in obesity, and (3) the introduction of a novel female conspecific.     

Facultative terrestrial hand postures in an orangutan (Pongo pygmaeus) and pongid evolution

An adult male orangutan at the Chicago Zoological Park utilizes various knuckle-walking hand postures in terrestrial bipedal-squatting and quadrupedal diagonal-sequence, diagonal-couplet gaits. A study was conducted in order to discern the circumstances surrounding the subject's terrestrial locomotor modes. It was found that various locomotor behaviors correlate with specific conditions of the substrate and the subject's motivation. Biomechanical properties of orangutan knuckle-walking are discussed in terms of their relevance for modelling hominoid phylogeny.     

Correction to: Comparative analysis of sperm motility in liquid and seminal coagulum portions between Bornean orangutan (Pongo pygmaeus) and chimpanzee (Pan troglodytes)

Primates - In the original publication of the article, the coauthor “Takashi Hayakawa” was wrongly assigned as co-corresponding author.     

Locomotor ecology of wild orangutans (Pongo pygmaeus abelii) in the Gunung Leuser Ecosystem, Sumatra, Indonesia: a multivariate analysis using log-linear modelling

The large body mass and exclusively arboreal lifestyle of Sumatran orangutans identify them as a key species in understanding the dynamic between primates and their environment. Increased knowledge of primate locomotor ecology, coupled with recent developments in the standardization of positional mode classifications (Hunt et al. [1996] Primates 37:363-387), opened the way for sophisticated multivariate statistical approaches, clarifying complex associations between multiple influences on locomotion. In this study we present a log-linear modelling approach used to identify key associations between orangutan locomotion, canopy level, support use, and contextual behavior. Log-linear modelling is particularly appropriate because it is designed for categorical data, provides a systematic method for testing alternative hypotheses regarding interactions between variables, and allows interactions to be ranked numerically in terms of relative importance. Support diameter and type were found to have the strongest associations with locomotor repertoire, suggesting that orangutans have evolved distinct locomotor modes to solve a variety of complex habitat problems. However, height in the canopy and contextual behavior do not directly influence locomotion: instead, their effect is modified by support type and support diameter, respectively. Contrary to classic predictions, age-sex category has only limited influence on orangutan support use and locomotion, perhaps reflecting the presence of arboreal pathways which individuals of all age-sex categories follow. Effects are primarily related to a tendency for adult, parous females to adopt a more cautious approach to locomotion than adult males and immature subjects.     

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。     

Locomotor behavior of wild orangutans (Pongo pygmaeus wurmbii) in disturbed peat swamp forest, Sabangau, Central Kalimantan, Indonesia

This study examined the locomotor behavior of wild Bornean orangutans (P. p. wurmbii) in an area of disturbed peat swamp forest (Sabangau Catchment, Indonesia) in relation to the height in the canopy, age-sex class, behavior (feeding or traveling), and the number of supports used to bear body mass. Backward elimination log-linear modeling was employed to expose the main influences on orangutan locomotion. Our results showed that the most important distinctions with regard to locomotion were between suspensory and compressive, or, orthograde (vertical trunk) and pronograde (horizontal trunk) behavior. Whether orangutans were traveling or feeding had the most important influence on locomotion whereby compressive locomotion had a strong association with feeding, suspensory locomotion had a strong association with travel in the peripheral strata using multiple supports, whereas vertical climb/descent and oscillation showed a strong association with travel on single supports in the core stratum. In contrast to theoretical predictions on positional behavior and body size, age-sex category had a limited influence on locomotion. The study revealed that torso orthograde suspension dominates orangutan locomotion, concurring with previous studies in dipterocarp forest. But, orangutans in the Sabangau exhibited substantially higher frequencies of oscillatory locomotion than observed at other sites, suggesting this behavior confers particular benefits for traversing the highly compliant arboreal environment typical of disturbed peat swamp forest. In addition, torso pronograde suspensory locomotion was observed at much lower levels than in the Sumatran species. Together these results highlight the necessity for further examination of differences between species, which control for habitat.     

Chromosome studies in the orangutan (Pongo pygmaeus): Practical applications for breeding and conservation

The unequivocal identification of Bornean, Sumatran, and first-generation hybrid orangutans can be carried out by chromosome analysis, a procedure that is more reliable than any other so far used to distinguish between orangutan subspecies. Chromosome differences between subspecies have been compared with protein and DNA studies, and these have shown that Bornean and Sumatran orangutans are more different from each other than we originally thought. Chromosome studies in the orangutan have shown variant chromosome types that are not subspecies-specific. One of these variant types is a product of a complex double inversion rearrangement and is a polymorphic trait in both subspecies. In view of our findings, specific guidelines have been recommended for evaluating the fertility of hybrid specimens and maintaining purebred orangutan stocks.