Wolf T E, Bennett N C, Burroughs R, Ganswindt A
Endocrine Research Laboratory, Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa; Department of Animal, Wildlife and Grassland Sciences, Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein 9300, South Africa.
Mammal Research Institute, Department of Zoology and Entomology, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria 0028, South Africa.
Gen Comp Endocrinol. 2018 Jan 1;255:26-31. doi: 10.1016/j.ygcen.2017.09.022. Epub 2017 Sep 28.
One of the primary sources of perceived stress is the social environment of an animal and the interactions with conspecifics. An essential component of the response to a stressor is the activation of the hypothalamic-pituitary-adrenocortical axis, which results amongst others in a temporal increase in circulating glucocorticoid (GC) levels. Giraffes occur in a highly flexible fission-fusion social system and group compositions can change on a daily basis, with bulls establishing an age-related dominance hierarchy and showing a roaming strategy in the search for fertile females. The aim of this study was to non-invasively monitor the influence of different group compositions (mixed sex groups vs. all-male groups) on GC concentrations in free ranging giraffe bulls of different age classes. We collected fecal samples from free-ranging giraffe bulls for 12months in a South African Private Game Reserve to examine age- and social context-related patterns of fecal GC metabolite (fGCM) concentrations. We found that fGCM levels in giraffe bulls are age-class dependent, as well asassociated with changes in the social environment. Independently of the social setting, bulls of the youngest age class exhibited the highest fGCM levels compared to bulls of the other two older age-classes, with differences most pronounced when the bulls are associated in all-male groups. In contrast, an almost reversed picture appears when looking at the fGCM levels of sexually active individuals in mixed sex groups, where highest levels were found for the bulls in the oldest age-class, and the lowest for the bulls in the youngest age-class. The study stresses the importance to taking factors such asage-related status and social settings into account, when interpreting fGCM levels in free ranging giraffes.
感知压力的主要来源之一是动物的社会环境以及与同种个体的互动。对应激源反应的一个重要组成部分是下丘脑 - 垂体 - 肾上腺皮质轴的激活，这尤其会导致循环糖皮质激素（GC）水平随时间增加。长颈鹿生活在高度灵活的裂变 - 融合社会系统中，群体组成每天都可能变化，雄性长颈鹿建立与年龄相关的优势等级制度，并在寻找可受孕雌性时表现出漫游策略。本研究的目的是无创监测不同群体组成（混合性别群体与全雄性群体）对不同年龄类别的自由放养长颈鹿雄性个体GC浓度的影响。我们在南非一个私人野生动物保护区对自由放养的长颈鹿雄性个体粪便样本进行了为期12个月的采集，以研究粪便GC代谢物（fGCM）浓度与年龄和社会背景相关的模式。我们发现，长颈鹿雄性个体的fGCM水平取决于年龄类别，并且与社会环境的变化有关。与其他两个年龄较大的年龄类别相比，无论社会环境如何，最年轻年龄类别的雄性长颈鹿表现出最高的fGCM水平，当雄性长颈鹿处于全雄性群体中时差异最为明显。相反，当观察混合性别群体中有性活动个体的fGCM水平时，情况几乎相反，年龄最大年龄类别的雄性长颈鹿fGCM水平最高，最年轻年龄类别的雄性长颈鹿fGCM水平最低。该研究强调在解释自由放养长颈鹿的fGCM水平时，考虑年龄相关地位和社会环境等因素的重要性。
