By Tanda Gmiter/MLive
ISLE ROYALE, MI – The annual report on Michigan’s Isle Royale wolf and moose populations has been released. And unlike recent years where island-watchers were just waiting to see if the remote island’s last two wolves had survived another year while the number of moose steadily ticked upward, this year’s report has a little drama tucked inside its pages.
There are new wolves to track, intense territorial patrolling by the two old island-born wolves, some bared-teeth rebuffing of incestuous courtship, and even some “unknown” wolf tracks that likely show a group of mainland wolves visited the island for a few days this winter and sampled some moose kill leftovers.
So grab your popcorn and we’ll take you through some of the report’s best highlights.
It’s compiled each year by researchers at Michigan Technological University. This winter, they spent four weeks tracking moose and wolves using planes and skis. Now in its 61st year, it is the world’s longest-running study of a predator-prey relationship.
Yes, there’s the expected rise in moose, this year topping 2,000. Their numbers have been allowed to grow nearly predator-free for years in the face of the island’s dwindling wolf pack. Their population is at near record-high levels, and their browsing diet is putting a big dent in the wilderness island’s vegetation, researchers found.
But the report also highlights some big moments among the wildlife on this Michigan island archipelago, which sits in Lake Superior about 15 miles from the Canadian mainland, and 60 miles from Michigan’s Upper Peninsula.
The National Park Service kicked off a multi-year wolf relocation project last fall in hopes more predators would keep the booming moose numbers in check. The two island-born wolves – an older, related pair that can’t have viable offspring – have been joined so far by 13 new wolves from Minnesota and Canada.
The Michigan Tech team was on the island during a window this winter when the island-born wolves and two new female wolves from Minnesota were there. The new wolves from Canada had not yet arrived, though recent GPS data from their tracking collarsshows how they are all fitting in.
Here are the highlights, new photos, and tracking maps, courtesy of the MTU study:
The only two island-born wolves left from Isle Royale’s old Chippewa Harbor Pack, this father-daughter pair had been the only wolves left on the island for several years.
Their family tree’s DNA is too twisted to result in viable pups. They share the same mother, too, so they are also half-siblings. A pup they had in 2014 was visibly deformed and died at about 9 months old, researchers estimate.
Still, the male, age 10, and the female, 8, remain “tightly bonded and highly territorial,” say researchers, who had good opportunity to study their movements in February and early March.
They were seen spending a lot of time patrolling the east end of Isle Royale, which is considered their home territory.
And as researchers have seen before with these two, the female wolf “soundly rejected the courtship advances of her father during the 2019 mating season,” even showing off her bared teeth, just to make sure she got her point across.
During their winter study, researchers estimated 10 moose kills by wolves, and another 2 moose that died likely due to an accident or possibly malnutrition, between Jan. 21 and March 2.
This means the island’s four resident wolves at that point were likely very well-fed.
A map included in the report shows the moose-kill spots.
During the bulk of the winter, just the two female Minnesota wolves and the island-born wolf pair were roaming the island. GPS trackers and overhead surveys showed the new arrivals were mostly keeping to themselves – and even traveled together at times – but their tracks crossed at enough points where the older wolves were surely aware of the Minnesota wolves’ presence, researchers said:
“The island-born pair remained together at the east end of the island. The two Minnesota-born females remained alone, at the far west end of the island through February. These two females, new to the island, killed moose calves on their own. They were unusually sedentary throughout February when mating usually occurs. They may have been positioning themselves for maximum exposure to any males that might travel the shorelines at the west end … However, the male Ontario-born wolves did not start arriving on the island until the very end of the breeding season and shortly thereafter. The movements and activity of all Minnesota-born and Ontario-born wolves will be closely monitored over the upcoming months via their GPS-collars by the NPS.”
While observing wolf movements on the island, researchers came across some unfamiliar tracks that didn’t originate from the two island-born wolves, or match up to the GPS-tracked movements of the new wolves.
Those tracks also generated some intense interest from the island-born wolf pair, who examined them at length.
Researchers believe these were wolves visiting from the mainland who crossed an ice bridge created by this year’s very cold winter winter weather. They shared a lot of fascinating details about this incident:
“On February 13, tracks of an unknown wolf were observed near Daisy Farm, the day after the island-born pair had been observed scent-marking the same area. On February 19, the island-born pair was observed in Lane Cove inspecting tracks that appeared to have been left by an unknown wolf, possibly different from the first unknown wolf as its tracks were very large. (We investigated both sets of tracks from the ground—giving us reason to think they were left by different-sized wolves.)
“On the same day, 10 miles to the southwest of Lane Cove, we followed tracks of three wolves off and on for 50 miles, beginning along the north shore of Isle Royale, then continuing all the way to the southwest end, on and over a couple offshore islands, around to the south shore of the island where the wolves fed on a moose carcass (which probably died from malnutrition). The tracks then continued along the shore to Houghton Point, at which point the tracks were lost as they crossed the vast expanse of ice covering Siskiwit Bay. The island-born pair spent much of February 19-25 patrolling their territory, following the unknown-wolf tracks and leaving prominent double scent-marks along the way.
“During the week that remained of the winter study, we flew the shorelines and much of the eastern interior, but found no more tracks that appeared to be from unknown wolves. It can be difficult to draw inferences from observing tracks when those tracks do not lead to directly observing the wolves that made them. However, it’s highly unlikely that these unknown wolf tracks could have been left by either of the two Minnesota-born female wolves because GPS data from these collared wolves places them at the other end of the island during this period.
“Our best (though fallible) inference is that several wolves arrived to Isle Royale by crossing the ice bridge and then returned to the mainland after spending approximately a week on Isle Royale in February. If that inference is incorrect and one or more of these putative wolves remained on Isle Royale, then there is a good chance of detecting their presence within the next 12 months through fecal DNA. Alternatively, if one or more of these putative wolves contributes reproductively to the island, then that contribution will eventually be detected through the fecal DNA of their offspring.”
Ice bridges have been used occasionally by wolves to access Isle Royale dating back decades that researchers know of – and possibly long before that.
It’s how the island’s first known wolves are believed to have walked there in the 1940s.
It’s believed to be the gateway for this winter’s “unknown” wolves to have visited for a week or so.
And it’s how one of the newly-transplanted wolves decided to go back to the mainland this winter. At the end of January, one of the three initial female wolves from Minnesota used an ice bridge created during the Polar Vortex freeze to travel back toward Canadaand Minnesota. Researchers tracked her via her GPS collar, and the Michigan Tech group followed up with a fly-over, seeing her tracks in the snow leading off the island and over the frozen ice, headed north.
Just as most people expected, the winter survey found a booming moose population on the island. The latest estimate is 2,060 moose packed onto the 206-square-mile archipelago.
The island’s balsam fir that makes up a good portion of the moose diet is suffering from the effects of their over-browsing, the report found. This underscores concerns that the large moose population is damaging the island wilderness
“We expect there might be a slowing down of moose population growth next year, at least at the west end of the island,” Sarah Hoy, an assistant research professor, said in an MTU news release. “The moose have severely damaged much of the vegetation they rely on during winter on the western end of the island.”
The fir tree effects were described in this sampling included in the study: “In 1988, 473 mature balsam fir trees were tagged on the western end of the island. Only 28 (6%) of those tagged trees remained in 2018. ”
To better study the island’s moose, 20 female moose were outfitted with GPS tracking collars. An early map of their travels is included.
Isle Royale’s beaver population has steadily increased since the wolf pack’s collapse in 2012. Wolves eat moose, but they also supplement their diets with beaver meat.
“An aerial count of active beaver colonies was conducted by Rolf Peterson (observer) and Don Murray (pilot), using float-equipped Aeronca Champ aircraft in October 2018. The 2018 survey resulted in the highest estimate of active beaver sites ever recorded for Isle Royale, 541 sites, which is consistent with the increasing beaver population documented since 2012.”
Red foxes, martens and snowshoe hares also find a home on Isle Royale.
The study says: “Red foxes were relatively uncommon in 2018–2019, as were their primary prey, snowshoe hares. Foxes are expected to fare much better over the winter as the wolf population grows and provides more moose carcasses that can be used by scavengers, such as foxes and ravens.”
For a remote island, Isle Royale has a lot going on. If you want to read more in-depth stories about its wolves, its history and what it has to offer, check out these features:
Tracking collars on Isle Royale’s new wolves show there is 1 place they won’t go.
The mysteries of Michigan’s Cemetery island.
Why moose were trapped, crated off this Michigan Island.
Necropsies detail deaths of 2 wolves in Isle Royale relocation effort