title: Seasonal variation in fecal testosterone levels in free-ranging male Japanese macaques.
abstract: Seasonal variation in fecal testosterone levels in free-ranging male Japanese macaques (Macaca fuscata) was examined with reference to their dominance rank and age class. Six adult (>or=7 years old, three higher-ranking and three lower-ranking) and four adolescent (5-6 years old, two higher-ranking and two lower-ranking) males were selected as target animals. Fecal samples of these males were collected during the first 3-5 days of each month and analyzed by the method developed by Barrett et al. [Primates 43:29-39, 2002 b]. Testosterone levels varied significantly across the 12 months, and were highest in the early and middle parts of the mating season (i.e., October and November). Higher-ranking adult males displayed a peak testosterone level in October, whereas lower-ranking adults had no clear peak in the mating season. Such a difference in testosterone peaks in males could provide higher-ranking males more opportunities to fertilize females at first ovulation in the mating season than lower-ranking males.
authors.affiliation: Department of Ecology and Social Behavior, Primate Research Institute, Kyoto University, Aichi, Japan. ymuro@pri.kyoto-u.ac.jp
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Muroyama
authors.forename: Keiko
authors.initials: K
authors.lastname: Shimizu
authors.forename: Hideki
authors.initials: H
authors.lastname: Sugiura
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D005243:Feces / Q000737:chemistry*; D006608:Hierarchy, Social; D007564:Japan; D008251:Macaca; D008297:Male; D011863:Radioimmunoassay; D012621:Seasons; D013739:Testosterone / Q000032:analysis*
chemical_list: D013739:Testosterone