Of mice, ticks and fleas: host behaviour and co-occurring parasites

Abstract

Host behaviour should be a key determinant of the acquisition of “sit-and-wait” and nidicolous ectoparasitic arthropods who ambush the host in their environment and/or nest. Here, we tested the association between parasitism and individual differences in exploratory and grooming behaviours in white-footed mice (Peromyscus leucopus Rafinesque, 1818), the primary host for the black-legged tick (Ixodes scapularis Say, 1821) in its larval stage. During 4,333 captures of 1,035 individual mice over 5 summers (2016-2020) in Ontario, Canada, the probability and intensity of tick parasitism were both significantly higher when the mouse was also parasitized by fleas, suggesting co-occurrence of these two parasites on host mice. Distance moved by mice in a novel environment was negatively and positively affected by tick and flea parasitism, respectively. Interestingly, there was a significant “tick×flea” statistical interaction on distance moved, such that fleas were positively associated with activity/exploration only when ticks were absent. There was no relationship between grooming behaviour and parasite presence. This study suggests that co-occurring parasite species (ticks and fleas) may differentially affect their host’s behaviour depending on the presence/absence of the other parasite on the host. Alternatively, host behaviour may differentially affect individual susceptibility to being infested with ticks, fleas, or both.