Fear and Foraging Behavior: Parasitic Infection Alters Risk Sensitivity in White-Footed Mice (Peromyscus leucopus)

The fear animals have of their predators can impact the way they behave while foraging for food. Infection with parasites may alter the way an animal perceives risk and, as a consequence, the way it forages. I examined whether wild white-footed mice (Peromyscus leucopus) foraged for food differently depending on whether they had been naturally infected with a helminth parasite or whether they had been experimentally cleared of infection. I compared their foraging behavior at foraging arenas that presented two microhabitats (open and covered). I also monitored predator abundance. In comparison with de-parasitized mice, mice that were infected with parasites significantly preferred to forage more in covered microhabitats and less under high predation risk. Parasitized mice also ate significantly more per individual than de-parasitized mice as population density increased. The results suggest that uninfected mice were less sensitive to perceived risk, but that they were more sensitive to actual predation risk. Furthermore, altered foraging behavior at increased densities suggests that that non-parasitized mice are more likely to leave familiar foraging patches in search of alternate food sources. Taken together, these results indicate that mice infected with helminthic parasites are likely to utilize more space in their home range and thus have higher encounter rates with incidental prey items and pathogen-carrying ticks