Examining the complex coexistence of wolves, moose

It makes sense that when wolf numbers swell in remote northeastern Minnesota, the moose herds they prey upon take a hit.

But a new study led by esteemed federal wolf researcher L. David Mech found a tight inverse relationship between Minnesota wolves and moose that isn't all bad news for the latter. When there have been fewer moose calves to feed on within a confined study area, mostly located in the Boundary Waters Canoe Area Wilderness, wolves have died off.

The relationship helps explain why moose numbers in northeastern Minnesota have been holding their own after crashing when wolf density was surging from 2002 to 2010. Since then, wolf counts in the study area east of Ely and north of Isabella have dropped significantly and moose numbers have stabilized.

"They [wolves] just don't have the calves to feed on," Mech said in an interview last week after the study he led from his office at the University of Minnesota was published by the quarterly journal Wildlife Society Bulletin.

Mech's recent work doesn't deny that brainworm, other parasites, climate-change factors or other mortality factors have dwindled populations of adult moose in Minnesota. His study focuses on moose calves and suggests the decline of northeastern Minnesota moose since 2006 "at least would not have been as steep without wolves' presence and influence."

The report gives ammunition to advocates of wolf hunting in Minnesota. The study doesn't address the issue, but Mech said his findings support the notion that harvesting wolves in his study area would boost the moose herd there. The hunting debate was put on ice last year when a federal appellate court upheld a lower court decision that kept gray wolves in Minnesota, Wisconsin and Michigan on the endangered species list. When the wolves were temporarily delisted, the DNR held limited wolf hunts for three years in a row.

"If wolf hunting were concentrated in that area and wolves were reduced, you'd probably see more moose," Mech said.

But he cautioned that his 800-square-mile study area is unique because deer do not winter there. In other parts of Minnesota's vast wolf range (about one-third of the state), wolves prey primarily on deer.

The wolf-moose correlation can be extrapolated outside of the study area, Mech said, but complexities arise as the distance from the study area increases. Mech is a senior scientist with the Biological Resources Division, U.S. Geological Survey, and an adjunct professor in the Department of Fisheries, Wildlife and Conservation Biology, and Ecology, Evolution and Behavior at the U of M. He has studied wolves and their prey since 1958.

Glenn DelGiudice, the DNR's moose biologist, said the new research isn't "earth-shattering" but is helpful to the overall research effort and management of moose, an iconic species numbering 9,000 animals in Minnesota as recently as 2006. The 2017 count was around 4,000.

DelGiudice said it would be interesting to conduct a measured wolf hunt in an area where moose are major targets of the apex predator. "If we could do that … we could see if it would readily help" the moose population, he said.

Like Mech, he noted that the study area inside the Superior National Forest is unique and small in comparison to the entire moose range. He also stressed the study doesn't delve into the critical importance of mortality in adult moose. But, DelGuidice said, "Wolves certainly are having a significant impact on the population" of Minnesota moose.

Mech's study relies on radio-collared wolves and population estimates from aerial surveys. It showed that wolf numbers in the study area rose from 44 in 2001 to nearly 100 in 2010. In that same period, the ratio of moose calves surviving their first winter dropped nearly threefold to a ratio of 0.24 calves for every adult female moose.

More recently there's been a reversal of the relationship. Mech said in his report there's been a "critical downward turn in the wolf population in our wolf-study area and an apparent response by moose."

The correlation is strong enough for Mech to predict that the DNR's 2018 moose population survey — to be announced within a couple of weeks — could show gains in moose numbers for the study area and extended terrain.