Natal versus breeding dispersal: behavioural tactics in first-time breeder roe deer females during mating

Natal dispersal is a widespread inbreeding avoidance mechanism that serves to spatially segregate opposite-sex relatives. However, little is known about the alternative behavioural tactics that philopatric individuals employ to avoid inbreeding. When natal dispersal is partial and not sex biased, females may perform reproductive excursions outside of their usual range. As a form of breeding dispersal, this could represent an alternative tactic to reduce the likelihood of mating with close relatives. To investigate this at the individual level, we analysed the spatial behaviour of 90 first-time breeder roe deer, Capreolus capreolus , females. Using data from intensive GPS monitoring, we classified individuals as either philopatric or disperser, and then identified excursions during their subsequent first mating season. While philopatric primiparous females were, on average, somewhat more likely to perform an excursion during the rut than dispersers, this difference was not significant. However, philopatric females on average moved farther from the boundaries of their home ranges than disperser females. Because philopatric females are likely to live in close proximity to related males, their fathers in particular, our results indicate that reproductive excursions could mitigate the risk of incestuous matings. This is the first demonstration of an interaction between natal dispersal and a specific form of breeding dispersal in a mammal. • Both philopatric and disperser roe deer females make excursions to breed. • Philopatric females make longer, not more, reproductive excursions than dispersers. • Females with less woodland in their home range make longer excursions. • Reproductive excursions may function as a partial alternative to natal dispersal. • Our findings highlight that natal and breeding dispersal interact in a mammal.