Spatio-temporal patterns of predation among three sympatric predators in a single-prey system

The manner in which species partition space and time to minimize competition for shared, limited resources has been a major focus of theoretical and empirical ecology. Although numerous examples exist of intra-guild dietary separation among coexisting species, studies of spatio-temporal partitioning among species sharing a single food type are rare. We investigated spatio-temporal patterns of multi-species predation on individually-marked moose Alces alces calves in an Alaskan boreal forest community where moose are the only large herbivore, and constitute the primary prey of coexisting black bears Ursus americanus, brown bears U. arctos and gray wolves Canis lupus. The two most closely related predators, black bears and brown bears, overlapped temporally and spatially in their consumption of moose calves, as indicated by univariate analyses. Moreover, both bear species segregated spatially from wolves when killing moose calves. Hence, our study appears to support key predictions of predator coexistence on a shared resource: namely, that bears and wolves differentiate spatially or temporally in their use of a pulsed prey, presumably to minimize competition.