Bales Karen L, French Jeffrey A, McWilliams Jennifer, Lake Reagan A, Dietz James M
Department of Biology, University of Maryland, College Park, 20742, USA.
Horm Behav. 2006 Jan;49(1):88-95. doi: 10.1016/j.yhbeh.2005.05.006. Epub 2005 Jun 22.
This study examines factors affecting androgen and cortisol levels in wild, male golden lion tamarins (Leontopithecus rosalia). Golden lion tamarins are a cooperatively breeding species in which groups often contain two potentially breeding males. Brothers frequently emigrate together and develop a clear dominance hierarchy, but interactions between them are primarily affiliative. Duos in which the males are not related are less stable. In addition, reproductive skew theory predicts that dominant males will be less likely to share reproduction with related subordinates. As such, we predicted that both androgens and cortisol would be higher in subordinate males unrelated to the dominant male. We also predicted that androgens in breeding males would be higher during the mating season than the birth/infant care season, as per Wingfield's "challenge hypothesis" (1990). Fecal samples were collected from 24 males in 14 social groups and assayed by enzyme immunoassay. Androgen levels were higher in breeding males during the mating season, thus supporting the challenge hypothesis. However, while subordinate males unrelated to the dominant male had significantly lower androgens than any other group, cortisol levels were not correspondingly higher. These results suggest that unrelated subordinate males show measurable reproductive suppression and may use strategies such as infantilization to avert aggression from dominant males.
本研究考察了影响野生雄性金狮狨（Leontopithecus rosalia）雄激素和皮质醇水平的因素。金狮狨是一种合作繁殖的物种，其群体中通常包含两只具有潜在繁殖能力的雄性。兄弟俩经常一起迁徙，并形成明确的优势等级制度，但它们之间的互动主要是亲和性的。雄性之间没有亲缘关系的配对则不太稳定。此外，生殖偏斜理论预测，占主导地位的雄性与有亲缘关系的从属雄性分享繁殖机会的可能性较小。因此，我们预测，与占主导地位的雄性没有亲缘关系的从属雄性体内的雄激素和皮质醇水平会更高。我们还预测，根据温菲尔德的“挑战假说”（1990年），繁殖期雄性的雄激素水平在交配季节会高于出生/幼崽照料季节。从14个社会群体中的24只雄性采集了粪便样本，并通过酶免疫测定法进行检测。交配季节繁殖期雄性的雄激素水平较高，从而支持了挑战假说。然而，虽然与占主导地位的雄性没有亲缘关系的从属雄性的雄激素水平显著低于其他任何群体，但其皮质醇水平并没有相应升高。这些结果表明，没有亲缘关系的从属雄性表现出可测量的生殖抑制，并且可能会采用诸如幼稚化等策略来避免来自占主导地位雄性的攻击。
