Werner Kaumanns

Male–Male Relationships in Lion-tailed Macaques (Macaca silenus) and Bonnet Macaques (Macaca radiata)

Socioecology suggests that female distribution in space is determined by the distribution of food resources and the male distribution is influenced by female distribution. Though studies have traditionally focused on females, males have received increasing attention in recent years. We compared male–male relationships in lion-tailed macaques and bonnet macaques. Because bonnet macaques have a high adult male:female sex ratio and are seasonal breeders whereas lion-tailed macaques have a low adult male:female sex ratio and are largely aseasonal breeders, we predicted that bonnet macaque males would be spatially and socially more tolerant of each other and would have less linear dominance relationships than lion-tailed macaques. We recorded male–male and male–female relationships in 1 group of wild macaques of each species via scan sampling and 1–0 sampling. The results revealed that lion-tailed macaque males largely remained at a distance from each other whereas bonnet macaque males remained in close proximity to one another. Lion-tailed macaque males were more agonistic toward each other whereas bonnet macaque males showed more affiliative interactions. The dominance hierarchy among lion-tailed macaque males was more linear than among bonnet macaque males. Our data support the hypothesis that the study of spatial structuring, temporality of interactions, and linearity of social relationships may contribute to a better understanding of macaque social systems.

Birth Patterns in Wild and Captive Lion-Tailed Macaques (Macaca silenus)

During a 5-yr study of lion-tailed macaques in their natural habitat, we found that: 1) most births occurred from January to April (70%) and from September to December (19%), showing a bimodal pattern with a major and a minor birth peak; 2) the period of peaks remained the same over 5 yr; and 3) a similar pattern of birth peaks occurred both in groups in large forest complexes that had overlapping home ranges with other groups and in single groups that were isolated in forest fragments in the same region but with similar ecological conditions. The results suggest more of a birth seasonality than mere breeding synchronization in the wild lion-tailed macaques. We also analyzed data on births in captivity in European Zoos for 10 yr. We observed no seasonality or peaks in births, and the pattern was the same over the years. Data on rainfall suggest that resource availability in the wild habitat may not be uniform throughout the year; hence, ecological factors may play an important role in determination of birth patterns in the natural habitats of lion-tailed macaques.

Distribution, Demography, and Conservation of Lion-tailed Macaques (Macaca silenus) in the Anamalai Hills Landscape, Western Ghats, India

The status of the endemic and endangered lion-tailed macaque (Macaca silenus) has not been properly assessed in several regions of the Western Ghats of southern India. We conducted a study in Parambikulam Forest Reserve in the state of Kerala to determine the distribution, demography, and status of lion-tailed macaques. We laid 5km2 grid cells on the map of the study area (644km2) and made four replicated walks in each grid cell using GPS. We gathered data on lion-tailed macaque group locations, demography, and site covariates including trail length, duration of walk, proportion of evergreen forest, height of tallest trees, and human disturbance index. We also performed occupancy modeling using PRESENCE ver. 3.0. We estimated a minimum of 17 groups of macaques in these hills. Low detection and occupancy probabilities indicated a low density of lion-tailed macaques in the study area. Height of the tallest trees correlated positively whereas human disturbance and proportion of evergreen forest correlated negatively with occupancy in grid cells. We also used data from earlier studies carried out in the surrounding Anamalai Tiger Reserve and Nelliyampathy Hills to discuss the conservation status in the large Anamalai Hills Landscape. This landscape harbors an estimated population of 1108 individuals of lion-tailed macaques, which is about one third of the entire estimated wild population of this species. A conservation plan for this landscape could be used as a model for conservation in other regions of the Western Ghats.

A Comparative Assessment of Hand Preference in Captive Red Howler Monkeys, Alouatta seniculus and Yellow-Breasted Capuchin Monkeys, Sapajus xanthosternos

There are two major theories that attempt to explain hand preference in non-human primates–the ‘task complexity’ theory and the ‘postural origins’ theory. In the present study, we proposed a third hypothesis to explain the evolutionary origin of hand preference in non-human primates, stating that it could have evolved owing to structural and functional adaptations to feeding, which we refer to as the ‘niche structure’ hypothesis. We attempted to explore this hypothesis by comparing hand preference across species that differ in the feeding ecology and niche structure: red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys, Sapajus xanthosternos. The red howler monkeys used the mouth to obtain food more frequently than the yellow-breasted capuchin monkeys. The red howler monkeys almost never reached for food presented on the opposite side of a wire mesh or inside a portable container, whereas the yellow-breasted capuchin monkeys reached for food presented in all four spatial arrangements (scattered, on the opposite side of a wire mesh, inside a suspended container, and inside a portable container). In contrast to the red howler monkeys that almost never acquired bipedal and clinging posture, the yellow-breasted capuchin monkeys acquired all five body postures (sitting, bipedal, tripedal, clinging, and hanging). Although there was no difference between the proportion of the red howler monkeys and the yellow-breasted capuchin monkeys that preferentially used one hand, the yellow-breasted capuchin monkeys exhibited an overall weaker hand preference than the red howler monkeys. Differences in hand preference diminished with the increasing complexity of the reaching-for-food tasks, i.e., the relatively more complex tasks were perceived as equally complex by both the red howler monkeys and the yellow-breasted capuchin monkeys. These findings suggest that species-specific differences in feeding ecology and niche structure can influence the perception of the complexity of the task and, consequently, hand preference.