Although still in its infancy, efforts to rebuild the Isle Royale wolf population and strengthen the Island’s wolves’ genetic diversity seem to be going well.
Earlier this week, the Isle Royale National Park and State University of New York-College of Environmental Sciences and Forestry (SUNY-ESF) released a report that documented reproduction for wolves introduced to Isle Royale in 2018 and 2019, a vital element of the National Park Service wolf introduction program’s success, globalwildlifecc.org/research/species-recovery/isle-royale-wolf-recovery.
GPS collar data and images from remote cameras suggest pups were born in 2019 and 2020, although an exact number of pups has yet to be determined.
Before the wolves’ transfer, there were two aging wolves on the 45-mile long, 143,000-acre Island: a male and female, likely a father and daughter who couldn’t mate and were suffering from genetic abnormalities.
GPS collar data from female wolf 014F, translocated from Michipicoten Island, Ontario, in March 2019, suggested denning in spring 2019. This wolf established several rendezvous sites that spring and summer. Images from a remote camera taken on September 29, 2019, revealed that wolf 014F likely gave birth to at least two pups. In addition, researchers at Michigan Technological University (MTU) observed a likely pup in February 2020, isleroyalewolf.org.
Genetic analyses of scats collected at one of the rendezvous sites will be conducted and if pups are confirmed, it suggests wolf 014F likely was pregnant before translocation to Isle Royale. We have no other evidence that reproduction occurred in 2019.
Analyses of GPS location data for wolf reproduction in 2020 supported denning activity in early April for female wolf 001F. This wolf, captured on the Grand Portage Indian Reservation, was the first wolf translocated to Isle Royale in September 2018. Her GPS collar attempted to obtain locations during early April 2020 but failed, indicating the collar was underground or in dense vegetation. Investigations of the den site in June 2020, after wolves had moved away, resulted in biologists collecting 18 pup-sized scats. Genetic analysis conducted on these scats will help determine the minimum number of pups born to wolf 001F.
Additionally, in July 2020, researchers obtained images from a remote camera of a single pup. Only a few hours later, an image of a single adult wolf at that same site was identified. Based on GPS data, this pup was born to a female wolf, 014F, or 015F. Visitors reported pup-sized tracks near this same location in early August. MTU researchers collected 13 pup-sized scats nearby, which will help determine the minimum number of pups in this litter.
“We can estimate the minimum number of pups born annually from scats collected at den and rendezvous sites, as well as monitor the genetic health of the population through time,” said Mark Romanski, NPS biologist and wolf introduction program coordinator at the park.
“Documenting reproduction is critical to the success of any introduction effort. In contrast to 2019, where female wolf 014F was likely pregnant before translocation, the breeding and rearing of two litters of pups this spring was a major step toward their recovery. We will continue to evaluate reproduction and recruitment of Isle Royale’s wolves using multiple lines of evidence including GPS collar data, remote cameras, DNA from wolf scats, and observations.” noted Dr. Jerry Belant, SUNYESF professor assisting the NPS with characterizing the wolf introduction program. Continuing to track this population closely will allow the NPS and its collaborators to evaluate the long-term success of the introduction and how wolves impact the ecosystem.
Wolves first came across on an ice bridge from Canada in either the late 1940s or as late as 1950, making a winter crossing when a portion of Lake Superior froze. Wolves (mostly) thrived on the Island until 2009 when the population started to crash. Their numbers fell from four healthy packs of 24 wolves to nine wolves and then finally to two.
Reasons for their demise are many, but interbreeding, disease, and wolves killing wolves are thought to be the main culprits.
Wolves play an important role in keeping the numbers of moose in check on the Island.
According to researchers, moose can live to be 17 years old and weigh as much as 1,800 pounds. On a typical summer day, they eat 40 pounds of vegetation. In the recent winter survey conducted by wildlife researchers, the moose population on the Island increased from 540 in 2011 to 750 in 2012. Today it is estimated that there are more than 1,800 moose on the Island.
In 2015 the NPS began having public meetings in Houghton, Michigan, Grand Portage, and at the park in Rock Harbor and Windigo, asking for input on whether or not to bring more wolves to the Island.
Before reaching a decision, the NPS looked at various alternatives for the management of moose, wolves, and vegetation on Isle Royale.
The moose-wolf-vegetation food web is tightly coupled, and the park’s final plan to reintroduce wolves took into account those relationships.
Climate change is also factored into the NPS decision. In the past, wolves would come from the mainland over winter ice, but the lake only freezes over every decade or so today, leaving less chance for new genes to be reintroduced to the breeding pool.
Researchers found that the remaining wolves were subject to inbreeding. Because of that, they were more susceptible to disease and to suffer from a deformity called lumbosacral transitional vertebrae.
To ensure there was genetic diversity, wolves were captured and moved from Canada, Minnesota, and Michigan to the Island.
Once the wolves were brought to the Island, they were radio-collared.
Using location data retrieved from global positioning system (GPS) collars, scientists monitored important aspects of wolf ecology, such as social organization, summer predation, mortality, and reproduction, to determine the project’s success. The NPS and research partners estimated as many as 14 wolves on Isle Royale as of April 2020.
“We are grateful to all our partners who worked tirelessly to support this historic restoration effort and we look forward to continuing our numerous collaborations that are helping to ensure we meet our objectives for restoring this apex predator to the Isle Royale ecosystem. We will now evaluate the program’s efforts to date to determine whether further translocations are warranted,” said Superintendent Denice Swanke, Isle Royale National Park.
To learn more about Isle Royale’s wolves and the introduction efforts, you can watch CuriosityStream’s original film Breakthrough: Return of the Wolves, produced in partnership with the National Parks of Lake Superior Foundation curiositystream.com/returnofthewolves and read the recently published summary report at www.nps.gov/isro/index.htm.
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