Seasonal changes of fecal testosterone levels and solicitation frequency in female Sichuan snub-nosed monkeys (Rhinopithecus roxellanae) in the Qinling Mountains

摘要

In order to study seasonal changes in testosterone levels and frequency of solicitation in wild female Sichuan snub-nosed monkeys (Rhinopithecus roxellanae), one group of wild golden monkeys in the Qinling Mountains was selected as the research target. By continuous tracking and observation, individual identification had been achieved for all 87 individuals in this group. Applying non-invasive sampling methods, we collected fecal samples and data on sexual behavior from three adult female monkeys. Fecal T (Testosterone, T) levels were measured by radioimmunoassay (RIA), after extracting the hormone from fecal samples. The results showed that fecal T levels in wild adult female monkeys displayed obvious cyclic fluctuations during dominant and non-dominant mating periods. In the dominant mating period, the mean length of cycles was 24.56 d±4.07 d and significantly shorter than that during the non-dominant mating period, (43.67 d±2.89 d.) The mean fecal T level was 2.85 ng±1.12 ng/g and the sexual solicitation frequency was 0.98±1.04 cases/d in the dominant mating period. Both of these measures were significantly higher than in the non-dominant mating period, (1.71 ng±0.77 ng/g and 0.28±0.53 cases/d, respectively). In the dominant mating period, frequencies of sexual behavior of every target individual significantly correlated with its fecal T level (the correlation coefficients were 0.631, 0.683 and 0.659, respectively). However, these correlations did not occur during non-dominant mating period (the correlation coefficients were 0.091, 0.493 and 0.205, respectively). This research suggests that the T levels, the T level cycle length and sexual solicitation frequency all undergo seasonal changes. Seasonal changes may be the intrinsic reasons and extrinsic exhibitions of seasonal reproduction in golden monkeys. In addition, this research also suggests that for adult female monkeys, frequencies of solicitation may be regulated by T levels during dominant mating period [Acta Zoologica Sinica 53(5): 783–790, 2007].