Food Webs

Photo: coyote © iStock.com/4loops

Declines in terrestrial predators

Most large native carnivores, including wolverine, have severely declined in abundance or have been extirpated from much of their ranges in the more populated regions of North America. Remaining ranges and larger populations are generally in the north and west of the continent.3

North American range of the wolverine
Map: North American range of the wolverine. Click for graphic description (new window).
Source: adapted from Hummel and Ray, 20083

In the Newfoundland Boreal Ecozone+, the wolf, a native top predator, was extirpated in the 1920s.4 Eastern coyotes, first sighted in the ecozone+ in 1987, have become a major predator, feeding on a variety of species and competing with native predators such as bear, lynx, and red fox.5

In the Mixedwood Plains Ecozone+, changes in predators and hunting, combined with milder winters and increased forage on lands altered by forestry and agricultural activities, have meant that populations of whitetailed deer have grown rapidly in recent decades.6, 7 Foraging by high numbers of deer has altered forest plant communities,8, 9 thereby affecting habitat for other species, including insects, birds, and small mammals.6

In the Prairies, the decline of the gray wolf began with the extirpation of the plains bison in the late 1800s and continued due to overharvest of ungulates and predator control.10 The loss of the wolf has changed predator-prey dynamics. In southeastern Alberta, western coyote abundance increased 135% between the periods 1977 to 1989 and 1995 to 1996.11

The change in top predators from wolves, which mainly hunted ungulates, to western coyotes, which eat a wider range of foods11, 12 and are not major ungulate predators,13 has shifted the abundance and distribution of prey species.