The social environment strongly affects the physiological stress response in group living animals, which in turn can affect the immune system and increase susceptibility to parasites. Here, I investigate relationships between social behavior and gastrointestinal parasite product excretion in the carrion crow (Corvus corone). Individuals from a population of non-cooperatively breeding carrion crows excreted less samples containing coccidian oocysts when kept in larger groups (8 or 9 individuals) compared to those individuals kept in smaller groups (2 or 3 individuals). Lower-ranking individuals excreted more samples containing parasite oocysts compared to higher-ranking individuals. The strength of affiliative relationships and number of related individuals in the group did not relate to the proportion of droppings containing coccidian oocysts. The present results confirm an association between social environment and parasite excretion patterns in carrion crows, but the patterns described in the present study differ from previously published data derived from a group of cooperatively breeding crows. This illustrates that differences between the social systems of carrion crows might result in different associations between the social environment and parasite product excretion patterns.

中文翻译：

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一组非合作繁殖的腐肉乌鸦中社会因素与胃肠道寄生虫产品排泄之间的关联

社会环境极大地影响了动物群的生理应激反应，进而会影响免疫系统并增加对寄生虫的敏感性。在这里，我调查了腐肉乌鸦（Corvus corone）中社交行为与胃肠道寄生虫产品排泄之间的关系。与分成小群（2或3个）的个体相比，以大群（8或9个个体）的个体，非合作繁殖的腐肉乌鸦群体的排泄出的样本较少，含有球虫卵囊。与等级较高的人相比，等级较低的人排泄了更多的含有寄生虫卵囊的样品。亲属关系的强度和相关个体的数量与包含球虫卵囊的粪便的比例无关。目前的结果证实了社会环境与腐肉乌鸦中寄生虫排泄模式之间的关联，但是本研究中描述的模式与先前发表的来自一组合作繁殖的乌鸦的数据不同。这说明腐肉乌鸦的社会系统之间的差异可能导致社会环境与寄生虫产品排泄方式之间的关联不同。