Increased exposure to pathogens is often considered to be one of the most significant costs of group living. As a result, animals typically avoid close association with individuals who manifest symptoms of disease. The question remains, however, whether avoidance behaviors are mediated by effects relating specifically to the disease itself, or through recognition of more general sickness behaviors that emerge from the activity of the immune system in response to infection. Here we examined the effects of an immune challenge, induced through exposure to bacterial lipopolysaccharides (LPS), on individual and social behavior in female guppies (Poecilia reticulata). We found that in a binary choice presentation, healthy focal individuals showed a strong preference to associate with stimulus shoals of saline-injected fish rather than stimulus shoals of LPS-injected fish. In a subsequent examination of group-level dynamics, shoals of LPS-injected females were more dispersed than similar shoals comprised of control fish and showed less coherent collective behavior despite the lack of any obvious difference in general activity between LPS and control fish. We discuss these findings in relation to the need for social animals to mitigate the risk of disease that is associated with living in proximity to conspecifics.

中文翻译：

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免疫挑战改变了孔雀鱼（Poecilia reticulata）的社会行为

增加接触病原体通常被认为是群体生活最重要的成本之一。因此，动物通常会避免与表现出疾病症状的个体密切接触。然而，问题仍然存在，回避行为是由与疾病本身相关的特定效应介导的，还是通过识别免疫系统响应感染的活动而出现的更普遍的疾病行为介导的。在这里，我们研究了通过接触细菌脂多糖（LPS）诱导的免疫挑战对雌性孔雀鱼（Poecilia reticulata）个体和社会行为的影响。我们发现，在二元选择呈现中，健康的焦点个体表现出强烈的偏好，与注射盐水的鱼的刺激浅滩相关，而不是与注射脂多糖的鱼的刺激浅滩相关。在随后对群体水平动态的检查中，注射 LPS 的雌性鱼群比由对照鱼组成的类似鱼群更加分散，并且尽管 LPS 和对照鱼之间的总体活动没有任何明显差异，但表现出不太连贯的集体行为。我们讨论这些发现与社会性动物需要降低与同种动物邻近生活相关的疾病风险有关。