A continental scale trophic cascade from wolves through coyotes to foxes

Area of Science:

• Ecology
• Wildlife Conservation
• Population Dynamics

Background:

• Top-down ecological processes, including competitive killing and intraguild predation, can shape terrestrial predator spatial distribution.
• Large-scale studies demonstrating these effects are rare, particularly concerning North American canids.

Purpose of the Study:

• To investigate the continental-scale spatial effects of grey wolf (Canis lupus) presence on coyote (Canis latrans) and red fox (Vulpes vulpes) densities.
• To determine if wolf extirpation has caused shifts in the distribution of subordinate predators.

Main Methods:

• Analysis of fur return data from eight North American jurisdictions.
• Statistical testing to correlate wolf presence/absence with red fox and coyote densities.

Main Results:

• A continent-wide cascade effect was observed: coyotes outnumbered red foxes in areas with wolf extirpation, while red foxes outnumbered coyotes where wolves were present.
• A 200 km transition zone at the edge of wolf distribution showed weakened top-down control, likely due to coyote dispersal into areas with low wolf density.

Conclusions:

• Wolf restoration can significantly impact co-occurring predator populations across North America.
• Large, continuous carnivore habitats are crucial for maintaining among-carnivore cascades and effective top-down mesopredator control.