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

Host behaviour should be a key determinant of the acquisition of sit-and-wait and nidicolous ectoparasitic arthropods that 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 4333 captures of 1035 individual mice over five 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 x 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.

Automated summary

Host behaviour plays a role in the acquisition of ectoparasites, and the presence of fleas affects tick parasitism in white-footed mice. Tick and flea parasitism have contrasting effects on the mice's movement in a novel environment, with ticks negatively affecting distance moved and fleas positively affecting it when ticks are absent. Grooming behaviour does not show a relationship with parasite presence. Co-occurring parasite species may differentially affect host behaviour or vice versa.