Kotrschal K, Hirschenhauser K, MÖSTL E
Konrad-Lorenz-Forschungsstelle and Institute for Zoology, Ethology Department, The University of Vienna
Anim Behav. 1998 Jan;55(1):171-6. doi: 10.1006/anbe.1997.0597.
Studies of captive animals have suggested that social stress affects subdominants, whereas recent data from the wild have revealed that stress mainly affects dominants. We used a non-invasive approach to investigate, for the first time in a social bird, the circannual stress-dominance relationships between low-ranking single males, intermediately positioned paired ganders without offspring and high-ranking paired males with offspring from a flock of semi-tame, free-ranging greylag geese, Anser anser. We collected 933 faecal samples from 43 individuals, 12 singletons, 18 paired males without offspring and 13 paired males with offspring over an entire year and analysed them for corticosterone metabolites by enzyme immunoassay. During the mating season (February-April), singletons had marginally higher corticosterone than paired males (P<0.1), whereas during the parental season (May-January), the paired males with offspring had significantly higher corticosterone than both paired males without offspring and singletons. All three male categories had significantly higher corticosterone during the mating season than during the rest of the year. These results suggest that social stress in ganders is caused mainly by competition between males and by constrained access to females during the mating season, but by parental commitment during the rest of the year. We suggest that dominance per se may not be a direct cause of stress. Rather, the amount of social stress may co-vary with the behavioural investment individuals need to make to optimize their fitness and with the relationship between such demands and the individuals' rank positions. This relationship seems to be seasonal in geese. Copyright 1998 The Association for the Study of Animal Behaviour.
对圈养动物的研究表明，社会压力会影响地位较低的个体，而最近来自野外的数据显示，压力主要影响占主导地位的个体。我们采用了一种非侵入性方法，首次在一种群居鸟类中研究了半驯化、自由放养的灰雁种群中低等级单只雄性、无后代的中等地位配对雄鹅以及有后代的高等级配对雄性之间的年度应激 - 优势关系。我们在一整年的时间里从43只个体（12只单只、18对无后代的配对雄性和13对有后代的配对雄性）收集了933份粪便样本，并通过酶免疫测定法分析其中的皮质酮代谢物。在交配季节（2月至4月）期间，单只雄性的皮质酮水平略高于配对雄性（P<0.1），而在育雏季节（5月至1月），有后代的配对雄性的皮质酮水平显著高于无后代的配对雄性和单只雄性。所有这三类雄性在交配季节的皮质酮水平均显著高于一年中的其他时间。这些结果表明，雄鹅中的社会压力主要是由交配季节雄性之间的竞争以及获取雌性的机会受限引起的，但在一年中的其他时间则是由育雏责任导致的。我们认为，优势地位本身可能不是压力的直接原因。相反，社会压力的大小可能与个体为优化自身适应性而需要进行的行为投入以及这种需求与个体等级地位之间的关系共同变化。这种关系在鹅中似乎是季节性的。版权所有1998动物行为研究协会。
