Food availability and long-term predation risk interactively affect antipredator response

Food availability and temporal variation in predation risk are both
important determinants of the magnitude of antipredator responses, but
their effects have rarely been examined simultaneously, particularly in
wild prey. Here, we determine how food availability and long-term
predation risk affect antipredator responses to acute predation risk by
monitoring the foraging response of free-ranging snowshoe hares (Lepus
americanus) to an encounter with a Canada lynx Lynx canadensis) in Yukon,
Canada, over 4 winters (from 2015-2016 to 2018-2019). We examined how this
response was influenced by natural variation in long-term predation risk
(two-month mortality rate of hares) while providing some individuals with
supplemental food. On average, snowshoe hares reduced foraging time up to
10 hours after coming into close proximity (≤ 75 m) with lynx, and reduced
foraging time an average of 15.28 ± 7.08 minutes per lynx encounter. Hares
tended to respond more strongly when the distance to lynx was shorter.
More importantly, the magnitude of hares’ antipredator response to a lynx
encounter was affected by the interaction between food-supplementation and
long-term predation risk. Food-supplemented hares reduced foraging time
more than control hares after a lynx encounter under low long-term risk,
but decreased the magnitude of the response as long-term risk increased.
In contrast, control hares increased the magnitude of their response as
long-term risk increased. Our findings show that food availability and
long-term predation risk interactively drive the magnitude of reactive
antipredator response to acute predation risk. Determining the factors
driving the magnitude of antipredator responses would contribute to a
better understanding of the indirect effects of predators on prey
populations.