Ectoparasite burden influences the denning behavior of a small desert carnivore

Abstract Quantifying the impacts of parasitism on a host can be arduous and is generally understudied for ectoparasites, with known works being either laboratory‐focused, correlational‐based, or only focusing on a few species and spatial extents. Many mammalian species have evolved the modality of denning behavior, a lifestyle that can lead to higher ectoparasite burden, and it has been posited that animals may alter their denning behavior in an attempt to reduce exposure to ectoparasites. We conducted a test of the ectoparasite release hypothesis for kit foxes ( Vulpes macrotis ) and fleas in the Great Basin Desert of the western United States, a hypothesis that has remained relatively untested for over half a century. We experimentally administered a flea reduction treatment to a subset of kit foxes. We then measured and compared the number of unique den usages and residency time across treatment and control foxes (no flea reduction treatment) while accounting for other factors known to influence denning behavior. Foxes treated with the flea medication reduced the number of unique dens and increased their residency times at dens. All kit foxes continued to use multiple dens on the landscape, suggesting several factors in addition to flea burden influence denning behavior. Our results confirm the long‐dormant ectoparasite release hypothesis and suggest ectoparasites may shape the behavior of burrowing vertebrates to a greater extent than previously recognized.