# Fallow deer approaching humans are more likely to be seropositive for Toxoplasma gondii

## TL;DR

This study found that fallow deer infected with Toxoplasma gondii are more likely to approach humans, suggesting a link between infection and risk-taking behavior.

## Contribution

The study provides new evidence that T. gondii infection may influence risk-taking behavior in free-living large mammals.

## Key findings

- Approximately 20% of the fallow deer population was seropositive for Toxoplasma gondii.
- Seropositive deer were more likely to exhibit risk-taking behaviors such as approaching humans.
- No correlation was found between T. gondii seropositivity and proximity to human infrastructure.

## Abstract

Toxoplasma gondii infection has been linked to dampening hosts anti-predator behaviour particularly in laboratory conditions with rodents. Little is known about the role of T. gondii within more complex ecological contexts involving large mammals. Therefore, we aimed to determine the prevalence of T. gondii infection in a population of free-living fallow deer (Dama dama). In addition, we assessed whether there was a link between deer seropositivity and space use where deer may be more likely to be exposed to T. gondii (e.g. closer to human infrastructure). Finally, we determined whether infection with T. gondii was linked to deer risk-taking behaviour. To achieve our goals, we estimated seropositivity and combined it with spatial distribution and behavioural data of individually recognizable deer ranging from those that avoid humans (risk avoiders) to those who beg for food (risk takers). We found T. gondii to be quite widespread in this population with a seropositivity rate of approximately 20%. We found no correlation between T. gondii seropositivity and space use in the park, therefore we were unable to determine how the deer were exposed. We did however find that seropositive deer were also more likely to take risks, opening new avenues to explore T. gondii’s dynamics in the wild.