Abstract
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.
Highlights
Grooming is a common form of affiliative behavior in various mammalian species of ungulates, rodents, and carnivores, and is especially important for species with complex social systems such as primates [1,2]
Study Site The study was conducted in the Yuhuangmiao region of Zhouzhi National Nature Reserve (ZNNR), which is located on the northern slope of the Qinling Mountains, Shaanxi Province, China. (2108u149–108u189E, 33u459–33u509N, elevation: 1,400– 2,896 m above sea level)
Power differentials that result from social status can offset strict reciprocation and influence the dynamics of grooming between individuals in nonhuman primate species
Summary
Grooming is a common form of affiliative behavior in various mammalian species of ungulates, rodents, and carnivores, and is especially important for species with complex social systems such as primates [1,2]. Social primates devote a significant proportion of their time (2%–5%) to exchanging grooming with their conspecifics [3,4]. The ‘hygienic hypothesis’ states that the primary function of grooming is to assist in removing ectoparasites from body areas that the beneficiary cannot reach [5,6]. This hypothesis does not satisfactorily explain grooming on body areas accessible to the beneficiary [7,8]. Social functions of grooming have been widely suggested as a way to establish harmonious relationships between group members and for the maintenance of social affinity [13,14]
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