Abstract
Predators play a critical, top-down role in shaping ecosystems, driving
prey population and community dynamics. Traditionally, studies of
predator-prey interactions have focused on direct effects of predators,
namely the killing of prey. More recently, the non-consumptive effects of
predation risk are being appreciated; e.g., the Ecology of Fear. Prey
responses to predation risk can be morphological, behavioural, and
physiological, and are assumed to come at a cost to prey fitness. However,
few studies have examined the relationship between predation risk and
survival in wild animals. We tested the hypothesis that predation risk
itself could reduce survival in wild-caught snowshoe hares. We exposed
female snowshoe hares to a simulated predator (a trained dog) during
gestation only, and measured adult survival and, in surviving females,
their ability to successfully wean offspring. We show for the first time
in a wild mammal that the risk of predation can itself be lethal.
Predation risk reduced adult female survival by 30%, and had
trans-generational effects, reducing offspring survival to weaning by over
85% - even though the period of risk ended at birth. As a consequence of
these effects the predator-exposed group experienced a decrease in number,
while the control group substantially increased. Challenges remain in
determining the importance of risk-induced mortality in natural field
settings; however, our findings show that non-lethal predator encounters
can influence survival of both adults and offspring. Future work is needed
to test these effects in free-living animals.