Threat detection: contextual recognition and response to parasites by ants

The ability of an organism to detect threats is fundamental to mounting a successful defense and this is particularly important when resisting parasites. Early detection of parasites allows for initiation of defense mechanisms, which are vital in mitigating the cost of infection and are likely to be especially important in social species, particularly those whose life history makes parasite pressure more significant. However, understanding the relative strength of behavioral responses in different species and situations is still limited. Here, we test the response of individual ants to fungal parasites in 3 different contexts, for 4 ant species with differing life histories. We found that ants from all 4 species were able to detect fungi on their food, environment, and nest mates and initiate avoidance or upregulate grooming behaviors accordingly to minimize the threat to themselves and the colony. Individuals avoided fungal-contaminated surfaces and increased grooming levels in response to fungal-contaminated nest mates. Ants from all species responded qualitatively in a similar way although the species differed quantitatively in some respects that may relate to life-history differences. The results show that ants of multiple species are capable of recognizing fungal threats in various contexts. The recognition of parasite threats may play an important role in enabling ant colonies to deal with the ever-present threat from disease.