The behavioral immune system in grey mouse lemurs: Causes of individual variation in behavioral defenses and consequences for socio-ecological traits

寄生虫介导的选择推动了宿主防御机制的出现，以限制寄生虫的传播。除了生理免疫系统(‘Ψis’)，动物还发展了一种“行为免疫系统”(‘βis’)，它包括一套复杂的抗寄生虫策略，如避免受污染的底物或受感染的共生物质。个体对行为防御的投资程度不同，这可能导致寄生虫在种群内分布的异质性，并对物种的社会生态特征产生深远的影响。为了最大化它们的健康，动物应该在ΨIS和β之间平衡投资，因为这两个系统都会产生能量成本。然而，抗寄生虫行为变异的决定因素仍然知之甚少，很少有研究调查βIS和ΨIS表达之间的相互作用。为了对这个新兴的研究领域做出贡献，我提议研究灰鼠狐猴(Microcebus Murinus)的抗寄生虫行为。这种夜间活动的马达加斯加灵长类动物表现出一种罕见的兼性社会性：一些动物在白天形成睡眠联系，而另一些动物则独自睡觉。初步工作表明，该物种表现出几种抗寄生性行为，个体在避免寄生虫方面表现出多样性。在第一部分，使用对圈养和野生动物进行的行为测试，我将调查寄生虫避免行为的个体间差异的原因。特别是，我将测试(1)群体生活的个体是否比单独生活的个体在行为防御上投入更多，以应对寄生虫介导的社交成本，以及(2)行为防御是否可以弥补糟糕的或暂时受损的个人免疫能力。在第二部分中，我将采用相关和实验相结合的方法，调查这些回避行为对他们睡眠生态的几个方面的影响。特别是，我将测试(1)巢寄生虫污染是否会影响睡眠场所的使用模式，以及(2)个别寄生虫的状态是否会影响睡眠关联。该项目有可能阐明β在宿主和寄生虫之间的共同进化动态中所发挥的关键作用。

Parasite-mediated selection has driven the emergence of host defense mechanisms to limit the spread of parasites. In addition to the physiological immune system (‘ΨIS’), animals have developed a “behavioral immune system” (‘βIS’), which comprises a sophisticated set of anti-parasitic strategies, such as avoidance of contaminated substrates or infected conspecifics. Individuals vary in their degree of investment in behavioral defenses, which may contribute to heterogeneity in parasite distribution within populations and have far-reaching consequences for socio-ecological traits of species. To maximize their fitness, animals should balance investment between ΨIS and βIS because both systems incur energetic costs. However, the determinants underlying variation in anti-parasitic behavior remain poorly understood and few studies have investigated interactions between expression of βIS and ΨIS. To contribute to this emerging research field, I propose to investigate anti-parasitic behaviors in grey mouse lemurs (Microcebus murinus). This nocturnal Malagasy primate exhibits a rare form of facultative sociality: some animals form day-time sleeping associations while others sleep alone. Preliminary work revealed that this species exhibits several anti-parasitic behaviors and that individuals show variation in parasite avoidance. In a first part, using behavioral tests conducted on both captive and wild animals, I will investigate causes of inter-individual variation in parasite avoidance behaviors. In particular, I will test (1) whether group-living individuals invest more in behavioral defenses than their solitary counterparts to cope with parasite-mediated costs of sociality, and (2) whether behavioral defenses may compensate for poor or temporarily compromised individual immuno-competence. In a second part, combining a correlative and an experimental approach, I will investigate the influence of these avoidance behaviors on several aspects of their sleeping ecology. In particular, I will test (1) whether nest parasite contamination influences sleeping site usage patterns and (2) whether individual parasite status influences sleeping associations. This project has the potential to shed light on the crucial role played by the βIS in the co-evolutionary dynamics between hosts and their parasites.