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.