Effects of Troop Size on Social Relations among Male Formosan Macaques, Macaca cyclopis

Hsu (2008) Effects of troop size on social relations among male Formosan macaques, Macaca cyclopis. Zoological Studies 47(3): xxx-xxx. We investigated the effects of troop size on differences in grooming and agonistic behaviors among adult males (AMs) and adult females (AFs) of Formosan macaques (Macaca cyclopis) during mating and non-mating seasons. Data were recorded for a total of 1248.8 h in 2 free-ranging social groups from Aug. 2000 to Feb. 2003 at Mt. Longevity, Kaohsiung, southern Taiwan. The socionomic sex ratios of these 2 social groups were similar during the mating seasons (AM: AF=1: 1.8). Both troop and peripheral males had significantly higher frequencies of social grooming with AFs in the mating than in non-mating seasons. The types of males and social groups, however, had significant effects on the allogrooming frequency among AMs in the mating seasons but not in the non-mating seasons. Moreover, troop males had higher numbers of grooming partners than did peripheral males. Major grooming partners of troop males were adult females regardless of the seasons. Nonetheless, peripheral AMs had more male grooming partners seemingly to enhance male affiliative relations. Subordinate males were mostly receivers in grooming dyads with dominant males in the mating seasons, but the relationships changed during the non-mating seasons. Agonistic interactions occurred mainly during the mating seasons, and their frequency among peripheral males was 1.8 times that of troop males (p < 0.05). Formosan macaque AMs employ complex strategies to balance competition and affiliative relations and ultimately achieve reproductive success