Fear and loathing in a Great Lakes forest: cascading effects of competition between wolves and coyotes

Abstract

Larger predators can affect smaller predators through intraguild predation and competition, which in turn could have indirect effects on other consumers. We investigated whether gray wolves ( Canis lupus ) generate such effects by reducing predation by coyotes ( Canis latrans ) on snowshoe hares ( Lepus americanus ). We also examined whether wolves indirectly affect abundances of deer mice ( Peromyscus spp.) as part of a wolf–coyote–fox cascade. We compared habitat use by consumers in the high- and low-wolf-use areas of a Great Lakes forest (Wisconsin and Michigan, United States). Coyotes frequented high-wolf-use areas about half as much low-wolf-use areas, which coincided with a tripling of hare browse on saplings in high-wolf-use areas. Foxes ( Vulpes vulpes and Urocyon cinereoargenteus ) frequented high-wolf-use areas almost exclusively. Fewer mice occurred in high-wolf-use areas than low-wolf-use areas in 2011 (approximately one-half) and 2013 (approximately two-fifths), but not in 2012, possibly due to increased food supply. We conclude that wolves may generate cascading effects through changes in coyote distribution that benefit hares and foxes, while also reducing the deer mouse population in some years.