NPS considers relocating wolves to Isle Royale

On Dec. 16, the National Park Service released a draft environmental impact statement (DEIS) concerning the declining population of gray wolves (Canis lupus) in Isle Royale National Park, Michigan.

Isle Royale, the largest of several Lake Superior islands comprising the national park, is the location of the world’s longest-running study of predator-prey dynamics in a closed environment. Biologists have studied the predator-prey dynamics of wolves and moose (Alces alces) living on Isle Royale for over 50 years. However, a recent downward trend in the wolf population has the potential to drastically change the ecosystem on Isle Royale.

Historically, wolves would periodically move between the island and the mainland in winters when the lake waters froze. This preserved genetic diversity of the island’s wolf population by reducing the effects of inbreeding. Warmer winter temperatures in recent years have prevented the lake from freezing regularly, reducing genetic diversity and threatening population growth. Only two wolves were confirmed to be living on the island in 2016, leaving it unlikely that the population will rebound on its own.  The wolf population has averaged 22 individuals on the island over the past 65 years.

NPS must now decide how to address the decline of the island’s wolf population. The DEIS proposes four options for addressing the issue. Two options include either a long- or short-term relocation effort, where wolves would be moved from the mainland onto the island in order to increase the population.

A third option proposed by NPS is to not take immediate action, but instead witness first-hand how a reduced or absent wolf population impacts ecosystem dynamics on the island. This option would allow NPS to relocate wolves in the future if it was determined that an apex predator was necessary for ecosystem function.

The fourth, “no-action” alternative would direct NPS to continue the wolf management strategy currently in place on the island without implementing any changes, despite the population decline.

NPS will consider many factors when deciding what to do about the wolf population on Isle Royale, prioritizing management of the island ecosystem as a whole. Without a predator to keep populations in check, there is concern that moose populations will grow large enough to threaten vegetation and plant communities on the island.

Public comment will be accepted on the DEIS until March 15, 2017.

Header Image: Isle Royale National Park. ©Ray Dumas