Red squirrels exhibit antipredator behavioural changes in response to a native predator, the pine marten.

Prey that coevolve alongside their predators develop specific antipredator responses to reduce their predation risk. Red squirrels (Sciurus vulgaris) are one such prey species who share an evolutionary history with a predator, the pine marten (Martes martes). The recent resurgence of the pine marten has caused a decline in the invasive grey squirrel (Sciurus carolinensis) in Ireland; however, it has not had the same impact on the Irish red squirrel population. We used trail cameras to record pine marten and red squirrel visits to feeders and analysed the behaviour of the red squirrel following recent pine marten presence. We found that red squirrels displayed an enhanced antipredator response involving increased vigilance, and decreased feeding following a visit from a pine marten. This effect was strongest with increasing proximity to the pine marten visit and weakened over time. These results indicate that red squirrels can detect recent pine marten presence and assess the perceived risk of predation based on the time since the predator's visit. These behavioural adaptations and sensitivity to the recent presence of the pine marten are hypothesized to have allowed for the red squirrel population recovery, in direct contrast to the grey squirrel decline in Ireland.