The population of wolves on Lake Superior's Isle Royale is likely thriving, with several new pups born in recent years.
Researchers with Michigan Technical University, who have been studying the relationship between wolves and moose on the island since the 1950s, this week published its Isle Royale Winter Study.
This year's study is a bit different though. The COVID-19 pandemic prevented researchers from conducting their in-person wintertime survey on wolves and moose for the first time in 63 years, so there are no estimates of wolf or moose abundance for 2021.
However, researchers went to the island in the spring, where they learned the wolves produced at least two litters of pups.
“We recovered footage of a group of four wolf pups taken in January 2021 by remote cameras at the east end of Isle Royale,” Sarah Hoy, research assistant professor in Michigan Tech’s College of Forest Resources and Environmental Science, said in a statement. “Additionally, observations of tracks and scats left by wolf pups last fall at two different locations suggest that there were probably two different litters of pups living at the east end of the island in September 2020.”
Researchers note there may have been a third litter born last year on the west end of the island, too.
The researchers expect the wolf population has grown slightly or moderately since they were last counted in spring 2020, at which point there were 12-14 wolves, so long as there wasn't an unusually high death rate.
Hoy guesses there may be about 15 to 20 wolves on the island, the Detroit Free Press says.
Researchers are working with the U.S. National Park Service to identify death rates and the number of litters produced. A more formal wolf population estimate is in the works, with an initial summary of the data expected in July.
This is good news for the island's ecology, which has been struggling due to the decline in wolves and the increase in moose over the past two decades.
There were as many as 50 wolves on the island in the 1980s, but by the late 2010s, there were only two. Wolves get to Isle Royale via ice bridges on Lake Superior but in recent years the lack of ice on the lake prevented new wolves from moving to the island. As a result, the pack that lives on the island became inbred and developed genetic deformities, dooming their long-term survival.
And with few predators, the island's moose population thrived. This is a problem because eventually, the moose would eat themselves — and all the other animals on the island — out of forage, destroying Isle Royale National Park's ecosystem.
This led the National Park Service to trap wolves from Minnesota, Michigan and Canada, and introduced 19 of them to the island in 2018 and 2019.
Moose population likely declining
While the wolves seem to be doing well, the moose have been struggling on the island due to a lack of food and an abundance of ticks.
The moose herd was estimated at about 1,876 in 2020, with researchers expecting it to be much lower. Hoy guesses the moose population is down to about 1,500-1,600, the Detroit Free Press states.
Researchers weren't on the ground to count moose over the winter, but they did a spring vegetation survey and found most balsam fir saplings — a favorite of moose in the winter — had been browsed so severely they had either died or been left with only a few green branches, signaling moose are eating them faster than the trees can replace them.
This food shortage coupled with winter ticks being worse than normal made it rough for moose on the island.
Researchers observed moose this spring with very little fur left, indicating they bit or scratched it all off in an effort to get rid of the ticks. Thousands of ticks will attach to moose, requiring the animal to use a lot of energy to replace the blood the ticks suck over the winter.
This can exacerbate the effects of a food shortage, researchers said.
Researchers found 13 dead moose this spring, which is significantly higher than the one or two starved moose they typically find.
Researchers also continue to recover the remains of moose that were killed by wolves. However, they say the impact wolves had on the moose population over the past year is still unknown. Researchers will detail this in the 2022 winter field season.
They did note wolves seem to seek out moose that are young, sick or elderly as they're easier to kill and are less likely to hurt a wolf.
"In theory, if the moose population is not in very good shape, that could benefit wolves," Hoy told the Detroit Free Press. "But the other thing to consider is that stressed, weakened moose may be less likely to reproduce."
Isle Royale is about 14 miles off Grand Portage on Minnesota's North Shore but is technically part of Michigan.