The spatial and temporal variation in food abundance has strong effects on wildlife feeding and nutrition. Here we present the first long term study of the effects of variation in fruit availability and age/sex class on nutritional ecology of wild Bornean orangutans. We examined variation in nutrient intake of wild orangutans in living in a peat swamp habitat over a 7-year period at the Tuanan Orangutan Research Station in Central Kalimantan. We conducted 2,316 full-day focal follows on 62 habituated orangutans (Pongo pygmaeus wurmbii). We found differences in total energy and macronutrient intake across age-sex classes, controlling for metabolic body mass. Intake of both total energy and macronutrients varied with fruit availability, and preference of dietary items increased with their nutritional quality. Foraging-related variables, such as day journey length, travel time, and feeding time, also varied among age-sex classes and with fruit availability. Our results add to the growing body of literature suggesting that great variation in foraging strategies exists among species, populations, and age-sex classes and in response to periods of resource scarcity.

Since Darwin (1859), scientists have been puzzled by how behaviors that impose fitness costs on helpers while benefiting their competitors could evolve through natural selection. Hamilton's (1964) theory of inclusive fitness provided an explanation by showing how cooperative behaviors could be adaptive if directed at closely related kin. Recent studies, however, have begun to question whether kin selection is sufficient to explain cooperative behavior in some species (Bergm€ uller, Johnstone, Russell, & Bshary, 2007). Many researchers have instead emphasized the importance of direct fitness benefits for helpers in the evolution of cooperative breeding systems.Furthermore, individuals can vary in who, when, and how much they help, and the factors that affect this variation are poorly understood (Cockburn, 1998;Heinsohn, 2004). Cooperative breeders thus provide excellent models for the study of evolutionary theories of cooperation and conflict (Cant, 2012). K E Y W O R D Sallocare, cooperative breeding, kin selection, marmosets, tamarins

Indonesia’s peatlands experience frequent and intense wildfires, producing hazardous smoke with consequences for human health, yet there is a lack of research into adverse effects on wildlife. We evaluated the effects of smoke on the activity and energy balance of Bornean orangutans (Pongo pygmaeus wurmbii) in a peat swamp forest at the Tuanan Research Station, Central Kalimantan. We collected behavioural data and urine samples from four adult flanged males before, during, and after wildfires between March 2015 and January 2016. During fires, particulate matter (PM10) concentrations were hazardous. Orangutans increased rest time during and after the smoke period, and decreased travel time and distance and increased fat catabolism post-smoke. The increase in post-smoke ketones was not related to changes in caloric intake and was likely due to an increase in energy expenditure, possibly related to immune response. Results show that wildfire smoke negatively affects orangutan condition, and sustained research is needed to assess the magnitude of the threat to the long-term viability of this Critically Endangered species.

Primate loud calls have the potential to encode information about the identity, arousal, age, or physical condition of the caller, even at long distances. In this study, we conducted an analysis of the acoustic features of the loud calls produced by a species of Asian colobine monkey (simakobu, Simias concolor). Adult male simakobu produce loud calls spontaneously and in response to loud sounds and other loud calls, which are audible more than 500 m. Individual differences in calling rates and durations exist, but it is unknown what these differences signal and which other acoustic features vary among individuals. We aimed to describe the structure and usage of calls and to examine acoustic features that vary within and among individuals. We determined the context of 318 loud calls and analyzed 170 loud calls recorded from 10 adult males at an undisturbed site, Pungut, Siberut Island, Indonesia. Most calls (53%) followed the loud call of another male, 31% were spontaneous, and the remaining 16% followed a loud environmental disturbance. The fundamental frequency (F0) decreased while inter-unit intervals (IUI) increased over the course of loud call bouts, possibly indicating caller fatigue. Discriminant function analysis indicated that calls were not well discriminated by context, but spontaneous calls had higher peak frequencies, suggesting a higher level of arousal. Individual calls were distinct and individuals were mainly discriminated by IUI, call duration, and F0. Loud calls of older males had shorter IUI and lower F0, while middle-aged males had the highest peak frequencies. Overall, we found that calls were individually distinct and may provide information about the age, stamina, and arousal of the calling male, and could thus be a way for males and females to assess competitors and mates from long distances.

Asian colobines typically live in small one-male groups (OMGs) averaging five adult females, but Simias concolor (simakobu or pig-tailed langur) is considered an exception because mostly adult male-female pairs have been reported. However, based on their phylogenetic position and marked sexual dimorphism, simakobu are also expected to form OMGs with multiple females. The preponderance of small groups could be the result of human disturbance (hunting or habitat disturbance) reducing group size in the recent past. To investigate this possibility, we documented the demography of ten wild simakobu groups from January 2007 until December 2008 at an undisturbed site, the Peleonan Forest, Siberut Island, Indonesia. We assessed the population-specific size and composition of groups and documented demographic changes due to births, disappearances, and dispersals throughout our 2-year study. We found OMGs with 3.0 adult females on average in addition to all-male groups, but no adult male-female pairs. The ratio of 0.5 infants per adult female (and 0.64 births per female-year in focal groups) suggested that birth rates were similar to those of other Asian colobines. In 5.1 group-years, we observed six dispersal events and six temporary presences (i.e., less than 3 months' residency). Both males and females dispersed, and juveniles seemed to disperse more frequently than adults. To assess the impact of human disturbance on simakobu demography, we compiled data for seven additional populations from the literature and compared them using multiple regressions. Adult sex ratio and the number of immatures per group were influenced negatively by hunting and positively by habitat disturbance while reproductive rates were not significantly affected by either variable. These findings suggest that adult male-female pairs may result from hunting pressure reducing group size, and that conservation action to reduce hunting in the Mentawai Islands is needed to ensure the survival of this critically endangered species.