Sex differences in social behavior of juvenile Sichuan snub-nosed monkeys Rhinopithecus roxellana at Yuhuangmiao, Mt. Qinling, China

摘要

Between March 2005 and May 2006, we studied sex differences in the social behavior of seven juvenile (3 ♀, 4 ♂) Sichuan snub-nosed monkeys ( Rhinopithecus roxellana ) at Yuhuangmiao Village in the Zhouzhi National Nature Reserve on the north slope of Mt. Qinling, China. The behavioral categories recorded were social grooming , social play,expulsion from the group , mounting and aggression .We used focal animal sampling and instantaneous sampling techniques. The results showed that significant sex differences of mean frequency were found not only in social grooming (♀ 11.86%, ♂ 6.55%) including grooming of infants (♀ 3.64%, ♂ 1.26%) and grooming mother (♀ 4.61%, ♂ 2.70%), but also in social play (♂ 4.44%, ♀ 7.39%), being expelled (♀ 0.42, ♂ 1.98), mounting (♀ 0.034, ♂ 1.83) and aggression (♀ 0.043, ♂ 0.088). We divided the age period (2 to 3 years) into 4 stages.This showed that mean frequencies of grooming infants( in females) and mean frequencies of being expelled (in males )were highly positively correlated with development stages .These sex differences appear to reflect,in part, differences in the life histories of the two sexes. This developmental strategy is also a response to the natural selection pressure based on population level in evolution, and increase individual fitness and make population maintain [ Acta Zoologica Sinica 53(6): 939– 946, 2007].