Dispersal and endoparasites in roe deer

Natal dispersal is a complex process but what could be the role of endo-intestinal parasites in dispersal propensity, distance and date of departure? In our article “Parasite abundance contributes to condition-dependent dispersal in a wild population of large herbivore” we look at this question on a roe deer population inhabiting a fragmented and anthropogenic landscape in South-West France.

Parasite abundance has been shown to have major consequences for host fitness components such as survival and reproduction. However, although natal dispersal is a key life history trait, whether an individual’s decision to disperse or not is influenced by the abundance of parasites it carries remains mostly unknown. Current and opposing hypotheses suggest that infected individuals should either be philopatric to avoid the energetic costs of dispersal (condition dependence) or disperse to escape from heavily parasitised habitats.

Roe deer were capture during winter, we sample fresh faeces and we collared them with a GPS collared in order to follow their movement during approximately one year before to release them in site. Their natal dispersal behaviour could thus be evaluated with accuracy.

Collection of faeces sample during marking

Back to the field with a beautiful GPS collar

Our results show that dispersal propensity generally decreased with both increasing nematode abundance and with decreasing body mass. Within the dispersing segment of the population, individuals with high nematode abundance left their natal home range later in the season than less parasitised deer. These results clearly show that parasite abundance is an important component of condition-dependent dispersal in large herbivores. However, unexpectedly, three individuals that were both heavily parasitised and of low body mass dispersed. We suggest that this “leave it” response to high parasite levels in the natal habitat could represent a last ditch attempt to improve reproductive prospects, constituting a form of emergency life history strategy.

The authors through Lucie Debeffe, who has also taken the photos.

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