A field experiment reveals reciprocal effects of host personality and parasitism in wild lizards

Host behavior and parasite infection reciprocally interact, but this dynamic is rarely studied experimentally in the field with multiple behaviors. We investigated the interplay between parasitism and host behavior via an in situ experimental tick infestation of a wild population of sleepy lizards, Tiliqua rugosa. Using Bayesian models, we assessed the relationship between experimental infestation and lizard aggression and boldness before and after infestation. First, we tested whether lizard aggression and boldness prior to infestation predicted the probability of tick attachment in the infestation experiment. Second, we evaluated whether experimental infestation affected subsequent lizard aggression and boldness. We found that aggression and boldness related interactively with infestation: for unaggressive lizards, higher boldness was associated with reduced experimental infestation success, but the opposite occurred for aggressive individuals. Second, increased tick infestation did not affect post-infestation aggression, but tended to increase boldness. Taken together, these results highlight the potential for feedbacks between parasites and multi-dimensional host behaviors. Although behavior is known to affect parasite loads, and parasites, in turn, can affect host behavior, it is unclear how personality interacts with parasite infestation. We experimentally infected a wild lizard population with ticks to study how lizard personality interacted with parasite loads in complex feedback loops. We found that personality affected parasite loads and that parasites, in turn, affected hosts with different personality types in distinct ways.