Ecological Studies of Wolves on Isle Royale 2025-2026

In winter 2026, the wolf population was likely composed of 37 wolves, which is approximately 20 percent higher than the last population estimate of 31 wolves in 2023. The wolf population included three packs, each containing at least 10 wolves. All three packs raised pups over the past summer. This winter we observed evidence of courtship and breeding in all three packs, suggesting that pups will also be born to each pack in April 2026.

The estimated abundance of moose is 524, which is 38 percent lower than the last population estimate of 840 moose in 2024 (Fig. 1). Longer-term population trends suggest that there has been a 75 percent decline in moose abundance since 2019. That substantial decline in moose abundance appears to be due to moose recruitment rates being well below average for the past six years. Indeed, for the first time in 68 years, we observed no calves on survey plots during our annual moose census. In a typical year, about 13 percent of moose seen on survey plots are calves.

Wolf predation has continued to be a major cause of mortality for moose and has contributed to the ongoing decline in moose abundance over the past six years. Predation rate, the proportion of the moose population killed by wolves, was estimated to be 24 percent this year, which is one of the highest predation rates ever recorded on Isle Royale and well above the long-term average of 10 percent.

In short, the wolf population appears to be doing well; however, the moose population continues to decline and is now getting close to the lowest level of moose observed (385 moose in 2007).