Male social rank and food competition in a primate multi-level society.

OBJECTIVES: Social animals often have dominance hierarchies, with high rank conferring preferential access to resources. In primates, competition among males is often assumed to occur predominantly over reproductive opportunities. However, competition for food may occur during food shortages, such as in temperate species during winter. Higher-ranked males may thus gain preferential access to high-profitability food, which would enable them to spend longer engaged in activities other than feeding. MATERIALS AND METHODS: We performed a field experiment with a breeding band of golden snub-nosed monkeys, a species that lives in a multi-level society in high-altitude forests in central China. We provisioned monkey's high-profitability food during winter when natural foods are limited, and then recorded the times individual adult males spent engaged in different behaviors. RESULTS: Higher-ranking males spent less time feeding overall and fed on provisioned foods at a higher rate than lower-ranking males. Higher-ranking males therefore had more time to spend on alternative behaviors. We found no significant difference according to rank in times spent moving or resting. However, high-ranking males spend significantly longer on affiliative behaviors with other members of their social sub-units, especially grooming and being groomed, behaviors known to promote social cohesion in primates. DISCUSSION: We show that preferential access to high-profitability foods likely relaxes time-budget constraints to higher-ranking males. High-ranking males thus spend more time on non-feeding activities, especially grooming, which may enhance social cohesion within their social sub-unit. We discuss the potential direct and indirect benefits to high-ranking males associated with preferential access to high-value food during winter.

Observation of mother-perpetrated infanticide in golden takins ( Budorcas taxicolor bedfordi).

Infanticide by unrelated individuals is widely reported in the animal kingdom; however, little is known about cases perpetrated by a parent, particularly the mother. This article reports on three cases of mother-initiated infanticide in Qinling golden takins ( Budorcas taxicolor bedfordi) recorded from video and camera images. Based on previous reports in other animals, we propose that the infanticide events observed in golden takins were related to the parental manipulation mechanism - i.e., killing an unhealthy infant to allow the mother to invest more care in potentially healthy offspring, and gain more fruitful reproductive opportunities. This appears to be an evolutionary-based selection strategy, whereby a species can prosper and succeed under the challenges of natural selection. However, further studies on both captive and wild populations are required to answer the various questions raised from our observations.

Postconflict Conciliation within One-Male Breeding Units in Sichuan Snub-Nosed Monkeys in the Qinling Mountains, China.

This study analyzed conflict and postconflict (PC) conciliation between males and females within one-male breeding units in Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains, China. The PC matched-control and time rule methods were used to collect and analyze data recorded from September 2013 to June 2014. The conciliatory tendency among individuals following conflict was 82.07%, and affiliation occurred within a few minutes after the conflict, which was not significantly different between mating and nonmating seasons. The PC conciliation scenarios were different from those reported from captivity. Lumbar hold and grooming were the most common expressions in reconciliation. In addition, bystander affiliation was uniquely found, which may be associated with the more terrestrial locomotion of R. roxellana, compared with other colobines.

Satellite telemetry and social modeling offer new insights into the origin of primate multilevel societies.

Multilevel societies (MLS), in which polygynous reproductive units are nested in a larger social matrix, represent a highly complex social system documented only in a small number of mammalian species. Using long-term behavioural data, satellite telemetry and social network analysis, we present a new framework for understanding the function and social dynamics of the golden snub-nosed monkey MLS. Here we show that several one-male units form a cohesive breeding band that associates with one or more all-male units to form a herd. Herds seasonally aggregate and exchange members, thus facilitating gene flow and inbreeding avoidance. This MLS evolved from the aggregation of independent one-male, multifemale units that characterize ancestral Asian colobines; the evolutionary pathway leading to this MLS contrasts with that proposed for African papionins, which appear to have undergone internal fissioning of multimale-multifemale groups. The results suggest that both environmental and phylogenetic factors are important in the evolution of a primate MLS.

The use of camera traps to identify the set of scavengers preying on the carcass of a golden snub-nosed monkey (Rhinopithecus roxellana).

There exists very limited information on the set of scavengers that feed on the carcasses of wild primates. Here, we describe, based on information collected using a remote camera trap, carnivores consuming/scavenging the carcass of a wild golden snub-nosed monkey (Rhinopithecus roxellana) in the Laohegou Nature Reserve, Sichuan, China. During a 3 month behavioral and ecology study of a band of golden snub-nosed monkeys (March through May 2013), we encountered the carcass of an adult male (male golden snub-nosed monkeys weigh approximately 12-16 kg). After examining the dead monkey, we returned it to the death site and set out a camera trap to record the behavior and identity of scavengers. Over the course of 25 days, we collected 4145 photographs taken by the camera trap. Scavengers identified from these photographs include a masked civet (Paguma larvata), Asiatic black bear (Ursus thibetanus), large-billed crow (Corvus macrorhynchos) and the chestnut rat (Rattus fulvescens). No member of the golden snub-nosed monkey's social group, which was composed of approximately 120 individuals, was found to return to the general area of the death site. The masked civet fed principally on the face and intestines of the corpse at night, while the black bear consumed most of the body of the dead monkey during both the daytime and nighttime. These two taxa consumed virtually the entire carcass in one week. We suggest that the use of camera traps offers a powerful research tool to identify the scavenger community of a given ecosystem.

[Diversity and development of positional behavior in non-human primates].

In long-term evolution, wildlife in general and primates in particular have formed specific patterns of behavior to adapt to a diverse variety of habitat environments. Current research on positional behavior in non-human primates has been found to explain a great deal about primate adaptability diversification, ecology, anatomy and evolution. Here, we summarize the noted classifications and differences in seasonal, site-specific and sex-age positional behaviors while also reviewing the development and status of non-human primate positional behavior research. This review is intended to provide reference for the future research of non-human primates and aid in further research on behavioral ecology of primates.

Market powers predict reciprocal grooming in golden snub-nosed monkeys (Rhinopithecus roxellana).

Social grooming is a common form of affiliative behavior in primates. Biological market theory suggests that grooming can be traded either for grooming or other social commodities and services. When no other services are exchanged, grooming is predicted to be approximately reciprocated within a dyad. In contrast, the amount of reciprocal grooming should decrease as other offered services increase. We studied grooming patterns between polygamous male and female in golden snub-nosed monkeys (Rhinopithecus roxellana) from the Qinling Mountains of central China and found that about 29.7% of grooming bouts were reciprocated. However, the durations of grooming bouts offered and returned was asymmetrical within dyads. In bisexual dyads, more grooming was initiated by females than males, which became more pronounced as the number of females per one-male unit increased. The rate of copulation per day for each female was positively correlated with the total duration of grooming time females invested in males.. Females without an infant (non-mothers) directed more grooming towards females with an infant (mothers) and were significantly more likely to be non-reciprocated. There was a significant negative relationship between non-mother and mother grooming duration and the rate of infants per female in each one-male unit. High-ranking females also received more grooming from low-ranking females than vice versa. The rate of food-related aggressive interactions was per day for low-ranking females was negatively correlated with the duration of grooming that low-ranking females gave to high-ranking females. Our results showed that grooming reciprocation in R. roxellana was discrepancy. This investment-reciprocity rate could be explained by the exchange of other social services in lieu of grooming.