Knapp R, Moore M C
Department of Zoology, Arizona State University, Tempe 85287-1501, USA.
Horm Behav. 1995 Mar;29(1):85-105. doi: 10.1006/hbeh.1995.1007.
Hormonal responses to male-male interactions have been detected in some studies of vertebrates but not others. One hypothesis that may partially explain these discrepancies is that differences in the duration of male-male interactions cause different hormonal responses. In social systems based on dominance-subordinance hierarchies interactions often last longer than if exclusive territories are maintained. Tests of the hypothesis that encounter duration explains discrepancies in hormonal responses would be facilitated by a species that shows elements of both types of social systems, such as species in which males practice alternative reproductive tactics. We compared plasma levels of corticosterone and testosterone in males of the territorial morph of the tree lizard (Urosaurus ornatus) subjected either to short (15 min) male-male encounters or to long (7 days) dominance interactions. In the long interactions, dominant males had lower levels of corticosterone than did subordinate males over the first day, but this difference subsequently disappeared. In sharp contrast, winners of short-term encounters had elevated plasma corticosterone levels which peaked the day after the encounter. Thus, males isolated after a short encounter experienced an increase in corticosterone that was apparently inhibited in males who continued interacting with other males. The delayed increase in corticosterone after a short encounter may facilitate metabolic recovery from the encounter, mobilize metabolic substrates useful in subsequent encounters, or may alter subsequent behavior. The response does not appear to be simply recovery from exercise because in a second experiment males exercised for 15 min did not show a similar delayed increase in corticosterone the following day. Testosterone levels were also monitored and did not change in any of these treatments. These results demonstrate that the duration and the outcome of male-male interactions may each independently influence hormone levels.
在一些脊椎动物研究中检测到了对雄性间互动的激素反应，但在其他研究中却未检测到。一种可能部分解释这些差异的假说是，雄性间互动持续时间的不同会导致不同的激素反应。在基于优势-从属等级制度的社会系统中，互动往往比维持专属领地时持续的时间更长。一个同时具有两种社会系统特征的物种，例如雄性采取替代繁殖策略的物种，将有助于检验相遇持续时间解释激素反应差异这一假说。我们比较了树蜥（饰纹强棱蜥）领地形态雄性个体在经历短时间（15分钟）雄性间相遇或长时间（7天）优势互动后血浆中皮质酮和睾酮的水平。在长时间互动中，第一天主导雄性的皮质酮水平低于从属雄性，但这种差异随后消失。形成鲜明对比的是，短期相遇的胜者血浆皮质酮水平升高，在相遇后一天达到峰值。因此，短时间相遇后被隔离的雄性皮质酮水平升高，而持续与其他雄性互动的雄性中这种升高显然受到抑制。短时间相遇后皮质酮的延迟升高可能有助于从相遇中恢复代谢、调动在后续相遇中有用的代谢底物，或者可能改变后续行为。这种反应似乎不只是运动后的恢复，因为在第二个实验中，运动15分钟的雄性在第二天并没有出现类似的皮质酮延迟升高。睾酮水平也进行了监测，在所有这些处理中均未发生变化。这些结果表明，雄性间互动的持续时间和结果可能各自独立地影响激素水平。
