Hygienic personalities in wild grey mouse lemurs vary adaptively with sex.

Detecting the risk of infection and minimizing parasite exposure represent the first lines of host defence against parasites. Individuals differ in the expression of these behavioural defences, but causes of such variation have received little empirical attention. We therefore experimentally investigated the effects of several individual and environmental factors on the expression level of faecal avoidance in the context of feeding, drinking, sleeping and defecating in a wild primate population. We found a strong sex bias in the expression level of anti-parasite behaviours of grey mouse lemurs (Microcebus murinus), with only females strongly avoiding contaminated food, water and nests, and exhibiting selective defecation. Our results further suggest that individuals adapted their protective behaviours according to variation in intrinsic and ecological factors that may influence the cost-benefit balance of behavioural defences. Overall, individuals exhibited high consistency of investment in protective behaviours across behavioural contexts and time, suggesting that grey mouse lemurs exhibit different hygienic personalities. Finally, the global hygienic score was negatively correlated with faecal-orally transmitted parasite richness, suggesting that variation in behavioural defence has fitness consequences. We suggest that integrating inter-individual variation in behavioural defences in epidemiological studies should improve our ability to model disease spread within populations.