One of the goals for primate feeding ecology is to understand the factors that affect inter- and intra-specific variations. Therefore, a detailed description of basic feeding ecology in as many populations as possible is necessary and warrants further understanding. The black-and-white colobus (Colobus guereza) or guereza is widely distributed in Africa and is one of the well-studied colobines in terms of their feeding; they demonstrate considerable variation in their diets in response to local conditions. We studied the diet of a group of guerezas in the Kalinzu Forest, Uganda, for over 30 consecutive months using behavioral observation (4308 h in total), phenology, and vegetation surveys. A total of 31 plant species were consumed by the study group. This study group was predominantly folivorous; the majority of their feeding time was involved in feeding on young leaves (87%). However, during certain times of the year, fruits and seeds accounted for 45% of monthly feeding time. Young leaves of Celtis durandii were by far the most important food, which constituted 58% of the total feeding records. There was a significant increase in the consumption of fruits and flowers once young leaf availability was low, but their consumption of fruits did not significantly increase even when fruit availability was high. Their monthly dietary diversity increased as the number of available plants with young leaves declined, suggesting that much of the dietary diversity in the study group may be attributable to the young leaf portion of their diet. Our findings may help contribute to a better understanding of the dietary adaptations and feeding ecology of guerezas in response to local environmental conditions.
Tourists are attracted to the Bukit Melawati Kuala Selangor (BMKS) of Peninsular Malaysia, a small hill park, for both its status as a historical site and the free-ranging silvered langurs (Trachypithecus cristatus) that come for provisioning. We assessed the population trends and group sizes of T. cristatus over 10 years in the BMKS and examined their ranging patterns. Comparisons of observed populations between 2005 (190 individuals) and 2017 (193 individuals) revealed the stable demography and group sizes of the six T. cristatus groups in the BMKS. Based on a total of 185 location points of the six groups in 2017, their mean ranging area was 3.6 ha with a range of 0.86-6.93 ha with extensive spatial overlap. We also found a significant positive relationship between the six groups' ranges and group sizes in 2017. Additionally, qualitative ecological comparisons with a previous study on T. cristatus in 1965 (before provisioning) suggest that the artificial food supply in the study area could modify the population dynamics and socioecology of T. cristatus. The modifications might alter their range size and territoriality in the BMKS. Overall, we found that provisioning had negative effects on the ecology of T. cristatus in the BMKS. Therefore, modifying management policies, such as banning feeding and implementing educational programs, may contribute to their proper conservation.
The reproductive success of male primates is not always associated with dominance status. For example, even though male orangutans exhibit intra-sexual dimorphism and clear dominance relationships exist among males, previous studies have reported that both morphs are able to sire offspring. The present study aimed to compare the reproductive success of two male morphs, and to determine whether unflanged males sired offspring in a free-ranging population of Bornean orangutans, using 12 microsatellite loci to determine the paternity of eight infants. A single flanged male sired most of the offspring from parous females, and an unflanged male sired a firstborn. This is consistent with our observation that the dominant flanged male showed little interest in nulliparous females, whereas the unflanged males frequently mated with them. This suggests that the dominant flanged male monopolizes the fertilization of parous females and that unflanged males take advantage of any mating opportunities that arise in the absence of the flanged male, even though the conception probability of nulliparous females is relatively low.
The Bukit Merah Orang Utan Island (OUI) Foundation has been conducting behavioral and veterinary research on orangutans as an attempt at ex situ conservation. Since 2010, the Primate Research Institute, Kyoto University has been collaborating with OUI to promote environmental enrichment and infant rearing by biological mothers in addition to the continuous efforts of refining the veterinary management of the endangered species. In 2011, three Bornean orangutans (Pongo pygmaeus pygmaeus) were released on an island, called BJ Island, adjacent to OUI. This island is approximately 5.6 ha in size, and 635 trees belonging to 102 plant species were identified prior to their release. Behavioral monitoring of the released individuals has been conducted to evaluate their behavioral adaptation to the new environment. Two of the three released orangutans were born in the wild, whereas the youngest individual was born on OUI and expected to learn forest survival strategies from the two older individuals. One of the orangutans was pregnant at the time of release and subsequently gave birth to two male infants on BJ Island. The behavioral monitoring indicated that these orangutans traveled more and spent more time on trees following their release onto BJ Island. However, resting was longer for two females both on OUI and BJ Island when compared to other populations. The orangutans consumed some natural food resources on BJ Island. The release into a more naturalistic environment may help the orangutans to develop more naturalistic behavioral patterns that resemble their wild counterparts.
In animal husbandry, diets should help in maintaining a healthy body condition, support reproduction, and promote species-specific longevity. It is recommended to feed folivorous primates kept in zoos a high-fiber diet, i.e., leaves, although satisfying such a requirement is challenging in temperate regions because it is difficult to obtain fresh leaves, especially in autumn and winter. As equally important for their appropriate treatment, it is valuable to provide details of clinical reports of medical problems and pathological findings, although such clinical reports are rather limited. Therefore, in foregut-fermenting proboscis monkeys (Nasalis larvatus), we (1) described the individual clinical reports of renal disease and weight loss at the Yokohama Zoological Gardens in Japan, (2) determined the nutritional profile of the diets supplied to these animals because other potential triggers for their renal disease and weight loss could be excluded, (3) modified the diet regimen to minimize weight loss and the development of hypercalcemia and hypophosphatemia, and (4) assessed the effects of such dietary modification by comparing the body weight and the Ca and P concentrations and the Ca/P ratios in the blood before and after diet modification with a comparison of these measurements between zoo and free-ranging individuals. Based on the nutritional profile of the diets, we concluded that the reported cases of renal failure might be caused by consumption of leaves with a Ca/P ratio far above the appropriate level in autumn and winter. Additionally, the dietary modification of minerals and metabolizable energy achieved certain beneficial effects on zoo-kept proboscis monkeys.
Inferring the latent structures of social organisations is a central theme in animal ecology. Sophisticated theoretical frameworks underpin the study of various primate social systems. Single-file movements, defined as serially ordered patterns of animals, reflect intra-group social relationships and provide a key to understanding social structures. Here, we analysed automated camera-trapping data on the order of progression of single-file movements in a free-ranging group of stump-tailed macaques to estimate the social structure of the group. The sequence of single file movements showed some regularities, particularly for adult males. Social network analysis identified four community clusters (subgroups) corresponding to the social structures reported for these stumptailed macaques, i.e. males that had copulated more frequently with females were spatially clustered with females, but males that had copulated less frequently were spatially isolated from females. Our results suggest that stumptailed macaques move in regular, socially determined patterns that reflect the spatial positions of adult males and are related to the social organisation of the species.
Long-term monitoring data on population abundance and distribution are essential for developing and refining conservation strategies, particularly for endangered species like the proboscis monkey (Nasalis larvatus), for which data remain limited across much of their range in Borneo. Previous studies conducted in 2004/2005 and 2014 in the Klias Peninsula, western Sabah, northern Borneo, provided important insights into population trends and distribution. Building on this foundation, we reassessed the proboscis monkey population in 2022 after an 8-year interval and investigated changes in land use and land cover during the same period. Our findings indicate a lower overall estimate of population abundance (number of individuals); however, the number of observed groups is comparable to previous studies, suggesting some stability. Distribution patterns have remained relatively stable, with population strongholds in the central part of the Klias Peninsula, underscoring the continued importance of areas like Padas Damit Forest Reserve for proboscis monkey conservation. Our data also reveal concerning trends, including a decline in group sizes (number of individuals per group) within breeding units and the presence of very small populations in fragmented sites such as Bongawan, presenting ongoing conservation challenges. Our land-use and land-cover change findings further revealed that less than half of the available proboscis monkey habitats in this region are fully protected. Vegetation analysis showed that tree species richness positively influences proboscis monkey abundance, emphasizing the critical role of food resource diversity. These findings have important conservation implications for the long-term survival of this endangered primate in the Klias Peninsula region.