Do Wolves Protect Forests? Investigating the Link Between Wolf Density, Deer Browse, and Plant Recovery

Area of Science:

• Ecology
• Wildlife Conservation
• Forestry

Background:

• Large ungulate populations, such as white-tailed deer (Odocoileus virginianus), can negatively impact forest regeneration and biodiversity.
• Reintroducing large predators like wolves (Canis lupus) is a proposed solution to manage ungulate populations and mitigate ecosystem damage.

Purpose of the Study:

• To evaluate the effectiveness of wolves in protecting forest understory plants from excessive deer browsing.
• To assess the impact of wolf presence and density on deer browse intensity and understory plant communities.

Main Methods:

• Planted white oak, red oak, and zigzag goldenrod seedlings across a gradient of wolf density and residence time in northern Wisconsin.
• Monitored deer browse intensity and the frequency of 11 common understory plants at each study site.

Main Results:

• Wolf density and residence time showed weak negative effects on deer browse intensity, primarily when understory vegetation was abundant.
• The presence of common understory plants decreased with increasing wolf density, contrary to expected trophic cascade effects.
• The observed reduction in browse probability by wolves was insufficient to significantly improve forest regeneration or understory plant recovery.

Conclusions:

• The reintroduction of wolves has a limited capacity to control deer populations and mitigate their impact on forest understory communities.
• Current wolf densities and their interactions with vegetation are unlikely to restore forest regeneration threatened by high deer populations.