Infectious diseases can cause host mortality through direct or indirect mechanisms, including altered behavior. Diminished anti-predator behavior is among the most-studied causes of indirect mortality during infection, particularly for systems in which a parasite's life-cycle requires transmission from prey to predator. Significantly less work has examined whether directly-transmitted parasites and pathogens also reduce anti-predator behaviors. Here we test whether the directly-transmitted bacterial pathogen, Mycoplasma gallisepticum (MG), reduces responses to predation-related stimuli in house finches (Haemorhous mexicanus). MG causes conjunctivitis and reduces survival among free-living finches, but rarely causes mortality in captivity, suggesting a role for indirect mechanisms. Wild-caught finches were individually housed in captivity and exposed to the following treatments: 1) visual presence of a stuffed, mounted predator (a Cooper's Hawk (Accipiter cooperii)) or control object (a vase or a stuffed, mounted mallard duck (Anas platyrhynchos)), 2) vocalizations of the same predator and non-predator, 3) approach of a researcher to enclosures, and 4) simulated predator attack (capture by hand). MG infection reduced anti-predator responses during visual exposure to a mounted predator and simulated predator attack, even for birds without detectable visual obstruction from conjunctivitis. However, MG infection did not significantly alter responses during human approach or audio playback. These results are consistent with the hypothesis that predation plays a role in MG-induced mortality in the wild, with reduced locomotion, a common form of sickness behavior for many taxa, as a likely mechanism. Our results therefore suggest that additional research on the role of sickness behaviors in predation could prove illuminating.

中文翻译：

---

感染减少了家雀的反捕食行为

传染病可通过直接或间接机制（包括行为改变）导致宿主死亡。反捕食者行为减弱是感染期间间接死亡的研究最多的原因之一，特别是对于寄生虫的生命周期需要从猎物传播到捕食者的系统。研究直接传播的寄生虫和病原体是否也会减少反捕食者行为的工作明显减少。在这里，我们测试了直接传播的细菌病原体鸡毒支原体 (MG) 是否会降低家雀 (Haemorhous mexicanus) 对捕食相关刺激的反应。MG 引起结膜炎并降低自由生活雀的存活率，但很少引起圈养死亡，这表明间接机制的作用。野生捕获的雀类被单独圈养并接受以下处理：1) 目视存在填充的骑乘捕食者 (Cooper's Hawk (Accipiter cooperii)) 或控制对象 (花瓶或填充填充的挂载野鸭 (Anas) platyrhynchos))，2) 同一捕食者和非捕食者的发声，3) 研究人员进入围栏的方法，以及 4) 模拟捕食者攻击（手动捕获）。MG 感染减少了在视觉暴露于已安装的捕食者和模拟捕食者攻击期间的反捕食者反应，即使对于没有可检测到的结膜炎视觉障碍的鸟类也是如此。然而，MG 感染并没有显着改变人类接近或音频播放期间的反应。这些结果与捕食在 MG 诱导的野外死亡率中起作用的假设一致，运动减少，这是许多分类群的常见疾病行为形式，可能是一种机制。因此，我们的研究结果表明，对疾病行为在捕食中的作用的进一步研究可能具有启发性。