Parasite-mediated manipulation? Toxoplasma gondii infection increases risk behaviour towards culling in red deer.

Parasites can modify host behaviour to increase their chances of survival and transmission. is a globally distributed protozoan whose ability to modify host behaviour is well known in taxa such as rats and humans. Less well known are the effects on the behaviour of wild species, with the exception of a few studies on primates and carnivores. Taking advantage of a culling activity conducted in Stelvio National Park (Italy), the serological status of was studied in 260 individuals of red deer with respect to the risk of being culled. A temporal culling rank index was fitted as a response variable, and serological status as the main explanatory variable in linear models, accounting for covariates such as sex, age, jaw length, bone marrow fat and culling location. The overall seroprevalence of was 31.5%, and the selected models suggested that seropositive deer were culled earlier than seronegative ones, but this effect was only evident in females, in individuals with medium-good body condition, and in areas with greater human presence. Our results suggest that may be involved in risk behaviour in large herbivores, supporting its role as a facilitator of predation risk.