Recolonizing carnivores: Is cougar predation behaviorally mediated by bears? Cougar Killsite Data

Conservation and management efforts have resulted in population increases
and range expansions for some apex predators, potentially changing trophic
cascades and predatory behavior. Changes in sympatric carnivore and
dominant scavenger populations provide opportunities to assess how
carnivores affect one another. Cougars (Puma concolor) were the apex
predator in the Great Basin of Nevada, USA, for over 80 years. Black bears
(Ursus americanus) have recently recolonized the Great Basin and are known
to heavily scavenge on cougar kills; however, competitive interactions
between the two species in the Great Basin have yet to be examined. We
investigated kill sites of 31 cougars between 2009 and 2017 across a range
of bear densities to evaluate the impacts of sympatric, recolonizing bears
on cougar foraging behavior. We modeled the variation in feeding bout
duration (number of nights spent feeding on a prey item) and the
proportion of primary prey, mule deer (Odocoileus hemionus), in cougar
diets using mixed-effects models. We found that feeding bout duration was
driven primarily by the size of the prey item being consumed, local bear
density, and the presence of dependent kittens. The proportion of mule
deer in cougar diet across all study areas declined over time, was lower
for male cougars, increased with the presence of dependent kittens, and
increased with higher bear densities. In sites with feral horses (Equus
ferus), a novel large prey, cougar consumption of feral horses increased
over time. Our results suggest that higher bear densities over time may
reduce cougar feeding bout durations and may influence the prey selection
trade-off for cougars when alternative, but more dangerous, large prey are
available. Shifts in foraging behavior in multi-carnivore systems can have
cascading effects on prey items. This study highlights the importance of
measuring the impacts of sympatric apex predators and dominant scavengers
on a shared resource base and, thus, provides a foundation for monitoring
dynamic multi-predator/scavenger systems.