Department of Anthropology, Indiana University, Student Building 130, 701 E, Kirkwood Ave,, Bloomington, IN 47405 USA.
Biopsychosoc Med. 2010 Dec 9;4:21. doi: 10.1186/1751-0759-4-21.
Male members of primate species that form multi-male groups typically invest considerable effort into attaining and maintaining high dominance rank. Aggressive behaviors are frequently employed to acquire and maintain dominance status, and testosterone has been considered the quintessential physiological moderator of such behaviors. Testosterone can alter both neurological and musculoskeletal functions that may potentiate pre-existing patterns of aggression. However, elevated testosterone levels impose several costs, including increased metabolic rates and immunosuppression. Cortisol also limits immune and reproductive functions.
To improve understanding of the relationships between dominance rank, hormones and infection status in nonhuman primates, we collected and analyzed 67 fecal samples from 22 wild adult male chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda. Samples were analyzed for cortisol and testosterone levels as well as intestinal parasite prevalence and richness. 1,700 hours of observation data were used to determine dominance rank of each animal. We hypothesized that dominance rank would be directly associated with fecal testosterone and cortisol levels and intestinal parasite burden.
Fecal testosterone (but not cortisol) levels were directly associated with dominance rank, and both testosterone and cortisol were directly associated with intestinal parasite richness (number of unique species recovered). Dominance rank was directly associated with helminth (but not protozoan) parasite richness, so that high ranking animals had higher testosterone levels and greater helminth burden.
One preliminary interpretation is that the antagonist pleiotropic effects of androgens and glucocorticoids place a cost on attaining and maintaining high dominance rank in this species. Because of the costs associated with elevated steroid levels, dominance status may be an honest signal of survivorship against helminth parasites.
在形成多雄性群体的灵长类物种中，雄性成员通常会投入大量精力来获得和维持高支配地位。攻击性行为经常被用来获得和维持支配地位，而睾酮被认为是这种行为的典型生理调节剂。睾酮可以改变神经和肌肉骨骼功能，从而增强先前存在的攻击性模式。然而，升高的睾酮水平会带来几个代价，包括增加代谢率和免疫抑制。皮质醇也限制了免疫和生殖功能。
为了更好地理解非人类灵长类动物中支配地位、激素和感染状态之间的关系，我们收集并分析了来自乌干达基巴莱国家公园恩戈戈的 22 只野生成年雄性黑猩猩（Pan troglodytes schweinfurthii）的 67 份粪便样本。对样本进行了皮质醇和睾酮水平以及肠道寄生虫流行率和丰富度的分析。使用 1700 小时的观察数据来确定每个动物的支配地位。我们假设支配地位将直接与粪便睾酮和皮质醇水平以及肠道寄生虫负担相关。
粪便睾酮（而非皮质醇）水平与支配地位直接相关，睾酮和皮质醇都与肠道寄生虫丰富度（回收的独特物种数量）直接相关。支配地位与寄生虫（而非原生动物）丰富度直接相关，因此高排名的动物具有更高的睾酮水平和更高的寄生虫负担。
一种初步解释是，雄激素和皮质醇的拮抗多效性效应在该物种中对获得和维持高支配地位产生了代价。由于与升高的类固醇水平相关的代价，支配地位可能是对寄生虫生存的诚实信号。
