Sex‐differences in disease avoidance behavior vary across modes of pathogen exposure

Sex‐differences in disease susceptibility are widespread, and these
disparities are often compounded in cases where sexual dimorphism
increases exposure risk to parasites for one sex more than the other.
Studies rarely link sex‐differences in disease susceptibility to
sex‐differences in infection avoidance behavior. Yet, understanding the
intersection of hosts’ susceptibility to infection and infection avoidance
behavior is essential to predicting infection risk variation. Here, we use
the fruit fly Drosophila melanogaster and a generalist entomopathogenic
fungus, Metarhizium robertsii, which can be transmitted directly,
indirectly, and post‐mortem as a model host–pathogen system. We test
whether the relationship between susceptibility to infection and pathogen
avoidance behavior covaries with host sex. We first measured differences
in resistance between male and female flies after three different types of
exposure—direct, sexual, and environmental—to infectious fungal
conidiospores. Then, we tested whether male and female flies differed in
the likelihood of mating with infected partners and their avoidance of
food patches with increased infection risk. Females were more susceptible
to infection under all three exposure techniques. When confronted with an
infectious partner, females mated sooner than males. However, when given a
choice between an exposed partner and an unexposed partner, females take
longer to begin copulating compared with males, though neither sex was
more likely to choose the unexposed partner than expected by chance.
Neither male nor females flies avoided food patches containing infectious
conidiospores, though only females show an aversion to food sites
containing an infectious fly corpse. These experiments suggest that
sex‐differences in disease susceptibility may be counteracted via
differential pathogen avoidance behavior, though the strength of avoidance
behavior appears to vary across different contexts of infection risk.