Fallback Foods of Red Leaf Monkeys (Presbytis rubicunda) in Danum Valley, Borneo

Animals in Southeast Asia must cope with long periods of fruit scarcity of unpredictable duration between irregular mast fruiting events. Long-term data are necessary to examine the effect of mast fruiting on diet, and particularly on the selection of fallback foods during periods of fruit scarcity. No such data is available for colobine monkeys, which may consume substantial amounts of fruits and seeds when available. We studied the diet of red leaf monkeys (Presbytis rubicunda, Colobinae) in Danum Valley, Sabah, northern Borneo, using 25 mo of behavioral observation, phenology and vegetation surveys, and chemical analysis to compare leaves eaten with nonfood leaves. The monkeys spent 46% of their feeding time on young leaves, 38% on seeds, 12% on whole fruits, 2.0% on flowers, 1.0% on bark, and 1.2% on pith. They spent more time feeding on seeds and whole fruit when fruit availability was high and fed on young leaves of Spatholobus macropterus (liana, Leguminosae) as fallback foods. This species was by far the most important food, constituting 27.9% of the total feeding time, and the feeding time on this species negatively correlated with fruit availability. Consumed leaves contained more protein than nonconsumed leaves, and variation in time spent feeding on different leaves was explained by their abundance. These results suggest that red leaf monkeys show essentially the same response to the supra-annual increase in fruit availability as sympatric monogastric primates, increasing their seed and whole-fruit consumption. However, they depended more on young leaves, in particular Spatholobus macropterus, as fallback foods during fruit-scarce periods than did gibbons or orangutans. Their selection of fallback food appeared to be due to both nutrition and abundance.     

Gesture Use in Communication between Mothers and Offspring in Wild Orang-Utans (Pongo pygmaeus wurmbii) from the Sabangau Peat-Swamp Forest,Borneo

International Journal of Primatology - Research on captive and wild great apes has established that they employ large repertoires of intentional gestural signals to achieve desired goals. However,...     

Orangutan Energetics and the Influence of Fruit Availability in the Nonmasting Peat-swamp Forest of Sabangau,Indonesian Borneo

Data on energy intake and the effects of fluctuations in fruit availability on energy intake for African apes, and orangutans in mast-fruiting habitats, indicate that orangutans may face greater energetic challenges than do their African counterparts. Comparable data on orangutans in nonmasting forests, which experience lower fluctuations in fruit availability, have been lacking, however, complicating interpretations. We conducted a 46-mo study of orangutan energetics in the nonmasting Sabangau peat-swamp forest, Indonesian Borneo. Sabangau orangutans experienced periods of negative energy balance apparently even longer than in mast-fruiting habitats, as indicated by comparisons of observed energy intake with theoretical requirements and analysis of urinary ketones. Daily energy intake was positively related to fruit availability in flanged males, but not in adult females or unflanged males. This may represent different foraging strategies between age-sex classes and suggests that fruit availability is not always an accurate indicator of ape energy intake/balance. Urinary ketone levels were not generally related to fruit availability, daily energy intake, day range, or party size. This is probably due to low energy intake, and consequently high ketone production, throughout much of the study period. Comparisons with published results on African apes support the hypothesis that orangutans are unique among hominoids in regularly experiencing prolonged periods of negative energy balance. This has important effects on orangutan behavior and socioecology, and has likely been a key factor driving the evolutionary divergence of orangutans and African apes.     

Group composition,home range,and diet of the maroon leaf monkey (Presbytis rubicunda) at Tanjung Puting Reserve,Central Kalimantan,Indonesia

Maroon leaf monkeys (Presbytis rubicunda) were studied at the Orangutan Research Conservation Project study area at the Tanjung Puting Reserve in Central Indonesian Borneo for approximately 15 months in 1974, 1975, and 1977. Over 250 observation hr involving 300 encounters with the monkeys were logged. Troop size ranged from three to eight individuals in the nine troops surveyed with only one adult male being present in each troop. Home range size varied from 0.33 km² to 0.99 km² and correlated with troop size. Forty-six different food types were observed eaten by the maroon leaf monkeys; of these foods, 52% consisted of fruits, 36% of leaves, and 12% of flowers.     

Density and population estimate of gibbons (Hylobates albibarbis) in the Sabangau catchment, Central Kalimantan, Indonesia

We demonstrate that although auditory sampling is a useful tool, this method alone will not provide a truly accurate indication of population size, density and distribution of gibbons in an area. If auditory sampling alone is employed, we show that data collection must take place over a sufficient period to account for variation in calling patterns across seasons. The population of Hylobates albibarbis in the Sabangau catchment, Central Kalimantan, Indonesia, was surveyed from July to December 2005 using methods established previously. In addition, auditory sampling was complemented by detailed behavioural data on six habituated groups within the study area. Here we compare results from this study to those of a 1-month study conducted in 2004. The total population of the Sabangau catchment is estimated to be about in the tens of thousands, though numbers, distribution and density for the different forest subtypes vary considerably. We propose that future density surveys of gibbons must include data from all forest subtypes where gibbons are found and that extrapolating from one forest subtype is likely to yield inaccurate density and population estimates. We also propose that auditory census be carried out by using at least three listening posts (LP) in order to increase the area sampled and the chances of hearing groups. Our results suggest that the Sabangau catchment contains one of the largest remaining contiguous populations of Bornean agile gibbon.     

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.     

Survey of Hylobates agilis albibarbis in a logged peat-swamp forest: Sabangau catchment, Central Kalimantan

Few data are available on gibbon populations in peat-swamp forest. In order to assess the importance of this habitat for gibbon conservation, a population of Hylobates agilis albibarbis was surveyed in the Sabangau peat-swamp forest, Central Kalimantan, Indonesia. This is an area of about 5,500 km² of selectively logged peat-swamp forest, which was formally gazetted as a national park during 2005. The study was conducted during June and July 2004 using auditory sampling methods. Five sample areas were selected and each was surveyed for four consecutive days by three teams of researchers at designated listening posts. Researchers recorded compass bearings of, and estimated distances to, singing groups. Nineteen groups were located. Population density is estimated to be 2.16 (±0.46) groups/km². Sightings occurring either at the listening posts or that were obtained by tracking in on calling groups yielded a mean group size of 3.4 individuals, hence individual gibbon density is estimated to be 7.4 (±1.59) individuals/km². The density estimates fall at the mid-range of those calculated for other gibbon populations, thus suggesting that peat-swamp forest is an important habitat for gibbon conservation in Borneo. A tentative extrapolation of results suggests a potential gibbon population size of 19,000 individuals within the mixed-swamp forest habitat sub-type in the Sabangau. This represents one of the largest remaining continuous populations of Bornean agile gibbons. The designation of the Sabangau forest as a national park will hopefully address the problem of illegal logging and hunting in the region. Further studies should note any difference in gibbon density post protection.     

Food selection by two South-east Asian colobine monkeys (Presbytis rubicunda and Presbytis melalophos) in relation to plant chemistry

The diets of the banded leaf monkey ( Presbytis melalophos ) at Kuala Lompat in the Krau Game Reserve of West Malaysia and the red leaf monkey ( Presbytis rubicunda ) in Sepilok Virgin Jungle Reserve, Sabah, East Malaysia have been examined in relation to plant chemistry. Both monkeys spent about half their time eating foliage, and about half their time eating fruits and seeds. They both favoured leaves with high digestibility (due to relatively low levels of fibre) and high levels of protein, a combination found predominantly in young leaves and some flowers. The monkeys appeared to favour seeds and fruits with high concentrations of storage carbohydrates or fats, but not those rich in simple sugars. Selection of seeds and fruits was not correlated with protein content.
An analysis of the fibre and protein contents of foods showed that, on an annual basis, the two monkeys achieved a comparable intake for both items. However, these diets were obtained in radically different ways. Presbytis melalophos was able to eat foliage from many of the common tree species in its home range, whereas P. rubicunda relied on rare trees and lianas. This difference is attributed to the very high density of Dipterocarpaceae at Sepilok, a tree family that provides little food for colobines. The rarity of P. rubicunda's food plants at Sepilok is considered to be the main reason for the greater home range size and lower population density in comparison to P. melalophos.
Finally, the biochemical profiles of the young leaf diet of these two monkeys were compared with previously published information on two African and one south Indian colobines. In many respects the intake of supposed critical components, protein and fibre, showed marked similarities between different animals, considering contrasts in their habitats.     

Vegetation correlates of gibbon density in the peat‐swamp forest of the Sabangau catchment,Central Kalimantan,Indonesia

Understanding the complex relationship between primates and their habitats is essential for effective conservation plans. Peat‐swamp forest has recently been recognized as an important habitat for the Southern Bornean gibbon (Hylobates albibarbis), but information is scarce on the factors that link gibbon density to characteristics of this unique ecosystem. Our aims in this study were firstly to estimate gibbon density in different forest subtypes in a newly protected, secondary peat‐swamp forest in the Sabangau Catchment, Indonesia, and secondly to identify which vegetation characteristics correlate with gibbon density. Data collection was conducted in a 37.1 km² area, using auditory sampling methods and vegetation “speed plotting”. Gibbon densities varied between survey sites from 1.39 to 3.92 groups/km². Canopy cover, tree height, density of large trees and food availability were significantly correlated with gibbon density, identifying the preservation of tall trees and good canopy cover as a conservation priority for the gibbon population in the Sabangau forest. This survey indicates that selective logging, which specifically targets large trees and disrupts canopy cover, is likely to have adverse effects on gibbon populations in peat‐swamp forests, and calls for greater protection of these little studied ecosystems. Am. J. Primatol. 72:607–616, 2010. © 2010 Wiley‐Liss, Inc.     

Seed-eating by red leaf monkeys (Presbytis rubicunda) in dipterocarp forest of northern borneo

Data are presented on the feeding behavior ofPresbytis rubicunda at Sepilok, north Borneo. Emphasis is given to describing the fruit-eating behavior of this small colobine monkey, which specializes in eating seeds from large, dull-colored, and fleshless fruits. The seed predation is conspicuously different from the seed dispersal effected by sympatric monogastric primates and is characteristic of colobine frugivory at other forest sites. Most seed-eating occurred during the period of maximum fruit production and fewer small-seeded, animal-dispersed fruits were eaten at other times.     

Patterns of Fine Root Mass and Distribution along a Disturbance Gradient in a Tropical Montane Forest, Central Sulawesi (Indonesia)

Large parts of the remaining tropical moist forests of South-east Asia are encroached at their margins by selective logging, rattan harvesting and the establishment of small agroforest plantations under the rainforest canopy. These slight to heavy disturbances affect aboveground forest structure by reducing wood biomass and canopy cover; however, they may also have a profound impact on the belowground compartment. In a lower montane moist forest of Central Sulawesi, we studied the profile totals of fine root biomass (FRB_tot, roots <2 mm until 50 cm of soil depth) and of fine root necromass (FRN_tot), the vertical distribution of fine root mass, and the fine root live/dead ratio by root coring in 12 forest stands that represented a gradient in forest use (or disturbance) intensity (forest use type A: undisturbed natural forest, B and C: slightly or moderately disturbed forests with selective timber extraction, D: heavily disturbed cacao agroforest systems under a remaining rainforest cover; each forest types being replicated three times). FRB_tot decreased significantly from forest A to the disturbed B, C and D forests, and reached less than 60% of the FRB_tot value of A in the agroforest systems D. A similar decrease with increasing disturbance intensity was found for FRN_tot. Forest disturbance intensity had no significant influence on the vertical distribution of fine root biomass in the profiles. According to correlation and principal components analyses, fractional canopy cover was the most important factor influencing FRB_tot and FRN_tot, whereas diameter at breast height, stand basal area, stem density, soil pH and base saturation had only a minor or no influence on root mass. A reduction in canopy cover from 90% (forest type A) to 75% (types C and D) was associated with a reduction in FRB_tot by about 45% which indicates that timber extraction leads not only to canopy gaps but to corresponding ‘root gaps’ in the soil as well. We conclude that forest encroachment that is widespread in large parts of South-east Asia’s remaining rainforests significantly reduces tree fine root biomass and associated carbon sequestration, even if it is conducted at moderate intensities only.     

Discovery of Miller's Grizzled Langur (Presbytis hosei canicrus) in Wehea Forest Confirms the Continued Existence and Extends Known Geographical Range of an Endangered Primate

Miller's Grizzled Langur (Presbytis hosei canicrus) is one of the least known and rarest primates in Borneo. With a limited geographic range along the central coast of East Kalimantan and the highly degraded Kutai National Park, its former stronghold, this subspecies is now extremely rare and has been listed as one of the world's 25 most endangered primates. From June 6 to August 2, 2011, we carried out both direct observation and camera trap surveys at two mineral springs (sepans) in the Wehea Forest, East Kutai district, East Kalimantan. Presbytis hosei canicrus was observed at the large sepan on 3 of 6 observation days and at the small sepan on 2 of 3 observation days with up to 11 individuals observed in a single day at a single site. Camera traps recorded a per day capture rate of 0.72 at the small sepan and 0.25 at the large sepan and a per photo capture rate of 0.50 and 0.005, respectively. These data suggest relatively frequent occurrence of P. h. canicrus at the sepans, but the langurs are rarely encountered elsewhere in the Wehea Forest. The discovery of P. h. canicrus in the Wehea Forest confirms the continued existence of this endangered primate and is the first solid evidence demonstrating that its geographic range extends further inland than previously thought. It is not known whether the population of P. h. canicrus within Wehea Forest is large and stable enough to be considered viable, but it is likely part of a larger population that may possibly occur across surrounding protected forests and logging concessions. Surveying this potentially large population, and securing its protection, should be a priority measure for ensuring the continued existence of P. h. canicrus.     

Genetic characterization of Strongyloides spp. from captive, semi-captive and wild Bornean orangutans (Pongo pygmaeus) in Central and East Kalimantan, Borneo, Indonesia

Orangutans (Pongo spp.), Asia's only great apes, are threatened in their survival due to habitat loss, hunting and infections. Nematodes of the genus Strongyloides may represent a severe cause of death in wild and captive individuals. In order to better understand which Strongyloides species/subspecies infect orangutans under different conditions, larvae were isolated from fecal material collected in Indonesia from 9 captive, 2 semi-captive and 9 wild individuals, 18 captive groups of Bornean orangutans and from 1 human working with wild orangutans. Genotyping was done at the genomic rDNA locus (part of the 18S rRNA gene and internal transcribed spacer 1, ITS1) by sequencing amplicons. Thirty isolates, including the one from the human, could be identified as S. fuelleborni fuelleborni with 18S rRNA gene identities of 98·5-100%, with a corresponding published sequence. The ITS1 sequences could be determined for 17 of these isolates revealing a huge variability and 2 main clusters without obvious pattern with regard to attributes of the hosts. The ITS1 amplicons of 2 isolates were cloned and sequenced, revealing considerable variability indicative of mixed infections. One isolate from a captive individual was identified as S. stercoralis (18S rRNA) and showed 99% identity (ITS1) with S. stercoralis sequences from geographically distinct locations and host species. The findings are significant with regard to the zoonotic nature of these parasites and might contribute to the conservation of remaining orangutan populations.     

黑叶猴活动时间季节性变化

为全面了解黑叶猴(Trachypithecus francoisi)的生态习性和活动规律,从中探讨其对喀斯特石山生境的适应策略,从2001年3~12月,在广西扶绥珍贵动物保护区对一群黑叶猴进行了连续的跟踪观察,采用连续记录法收集相关的行为数据。结果表明,黑叶猴的日活动节律表现为上午和下午的觅食高峰,中午进入长时间的休息期。这可能与白天的温度和日照强度的变化有关。它们的活动节律具有明显的季节性变化,主要表现为雨季活动节律中的觅食高峰与旱季相比推迟1h出现;旱季觅食高峰中用于觅食的时间明显增加,且中午出现一个小的觅食高峰。在黑叶猴的活动时间分配中,平均65.4%的时间用于休息,19.6%用于觅食,9.9%用于移动,用于社会活动的时间平均仅占5.1%。它们的活动时间分配表现出明显的季节性变化。在旱季,用于觅食的时间明显多于雨季,而休息时间相应地减少。     

Hunting Primates and Managing Forests: The Case of Iban Forest Farmers in Indonesian Borneo

Hunting by Iban forest farmers in West Kalimantan, Indonesia, is an important part of their subsistence economy, and as such became a focus of study as part of a conservation project in the Danau Sentarum Wildlife Reserve. In this paper, we examine Iban hunting of nonhuman primates with comparison to other large mammals. We analyze rates of encounter and capture, comparing encounters, hunting trips, and animal numbers. Information on habitats hunted shows the importance of secondary and old growth forest. Also examined are Iban attitudes, game preferences, and taboos. The significance of these findings is discussed with regard to the threats to wildlife from increases in the use of shotguns, human population, and habitat destruction, showing that conservation may be aided by promoting or enhancing certain aspects of the traditional Iban agroforestry system.