Behavioral traits are likely to influence species vulnerability to anthropogenic threats and in consequence, their risk of extinction. Several studies have addressed this question and have highlighted a correlation between reproductive strategies and different viability proxies, such as introduction success and local extinction risk. Yet, very few studies have investigated the effective impact of social behaviour, and evidence regarding global extinction risk remains scant. Here we examined the effects of three main behavioral factors: the group size, the social and reproductive system, and the strength of sexual selection on global extinction risk. Using Primates as biological model, we performed comparative analysis on 93 species. The conservation status as described by the IUCN Red List was considered as a proxy for extinction risk. In addition, we added previously identified intrinsic factors of vulnerability to extinction, and a measure of the strength of the human impact for each species, described by the human footprint. Our analysis highlighted a significant effect of two of the three studied behavioral traits, group size and social and reproductive system. Extinction risk is negatively correlated with mean group size, which may be due to an Allee effect resulting from the difficulties for solitary and monogamous species to find a partner at low densities. Our results also indicate that species with a flexible mating system are less vulnerable. Taking into account these behavioral variables is thus of high importance when establishing conservation plans, particularly when assessing species relative vulnerability.

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Objectives: Parasite selection pressures have driven the evolution of numerous behavioral defenses in host species, but recent studies revealed individual variation in their expression. As little is known about the factors causing heterogeneity among individuals in infection-avoidance behaviors, we investigated in woolly monkeys (Lagothrix lagotricha poeppigii) the influence of several environmental and individual characteristics on the tendency to avoid food contaminated by soil and by their own and conspecifics' feces.Materials and methods: We conducted feeding tests on 40 semi-free ranging individuals rescued from the pet trade. Using generalized linear mixed models, we investigated the effect of season, sex, age, dominance rank, and exposure to non-natural living conditions on feeding decisions.Results: Woolly monkeys did not avoid soil-contaminated food and equally avoided food contaminated by their own and conspecifics' feces. Individuals varied greatly in their level of fecal avoidance. Only females exhibited strong avoidance of fecally contaminated food, but adapted their behavior to food availability, highlighting the trade-off between nutritional intake and parasite avoidance. Additionally, lowranking females, less competitive over food resources, exhibited lower avoidance than dominant ones. Juveniles were more cautious than adults, possibly to compensate for a higher parasite susceptibility. Finally, we reported an unknown effect of exposure to non-natural living conditions on behavioral defenses, as animals kept as household pets for an extended period apparently lost their ability to avoid fecally contaminated food. Conclusion:We argue that striving to understand variation in infection-avoidance behaviors in natural populations is crucial to predict disease spread and inform conservation policies.

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