Variation in fecal testosterone levels, inter‐male aggression, dominance rank and age during mating and post‐mating periods in wild adult male ring‐tailed lemurs (Lemur catta)

In primate species exhibiting seasonal reproduction, patterns of testosterone excretion in adult males are variable: in some species, peaks correlate with female receptivity periods and heightened male–male aggression over access to estrous females, in others, neither heightened aggression nor marked elevations in testosterone have been noted. In this study, we examined mean fecal testosterone ( f T) levels and intermale aggression in wild adult male ring‐tailed lemurs residing in three groups at Beza Mahafaly Reserve, Madagascar. Results obtained from mating and post‐mating season 2003 were compared to test Wingfield et al. [1990. Am Nat 136:829–846] “challenge hypothesis”, which predicts a strong positive relationship between male testosterone levels and male–male competition for access to receptive females during breeding season. f T levels and rates of intermale aggression were significantly higher during mating season compared to the post‐mating period. Mean f T levels and aggression rates were also higher in the first half of the mating season compared with the second half. Number of males in a group affected rates of intermale agonism, but not mean f T levels. The highest‐ranking males in two of the groups exhibited higher mean f T levels than did lower‐ranking males, and young males exhibited lower f T levels compared to prime‐aged and old males. In the post‐mating period, mean male f T levels did not differ between groups, nor were there rank or age effects. Thus, although male testosterone levels rose in relation to mating and heightened male–male aggression, f T levels fell to baseline breeding levels shortly after the early mating period, and to baseline non‐breeding levels immediately after mating season had ended, offsetting the high cost of maintaining both high testosterone and high levels of male–male aggression in the early breeding period. Am. J. Primatol. 69:1325–1339, 2007.