Wolves translocated to Isle Royale National Park over the last year are starting to form packs, with two wolves killed in fights with other wolves, a new report from the National Park Service states.
One of the wolves that died was a small male that had been one of the original two left on the island.
Wolves were brought to the Island to help stabilize the growing numbers of moose who are wreaking havoc on the island’s vegetation and to provide genetic diversity to the wolf population, which numbered two before the efforts to reintroduce new members of the canine family began.
According to the released data, the new wolves, which were fitted with global positioning collars (GPS) show that one female and two males have been traveling, feeding, and bedding together since March 2019.
This is the first wolf group to form and remain associated since introduction efforts began. Additionally, two male wolves shared bed sites and carcasses over the summer with several different female wolves, but their associations lack consistency and are currently not defined as wolf groups. Two female wolves shared bed site areas over the summer (July), but are also not considered a group.
Wolves’ island history
The first wolves documented on Isle Royale came in the 1940s by crossing an ice bridge. In 1958, Duward Allen of Michigan Tech led a wolf-moose predator prey project that was originally going to run for ten years. Today the study is ongoing and believed to be the oldest continuous project of its kind.
In the early ’80s there were 50 or so wolves on the island.
Thirty-five years later, in 2015, with the moose population soaring past 1,300, there were only three wolves left, and the sheer number of moose were causing over-browsing to the 45-mile-long, 143,000-acre Lake Superior emerald jewel.
Dr. Rolf Peterson, a wildlife ecologist who spent more than 40 years on the Michigan Tech predator/ prey study, said he was happy to learn about the park’s decision to bring additional wolves to the island. He and Dr. John Vucetich, an ecologist from Michigan Technological University (MTU) who joined Peterson in the early 1990s, were strong advocates for adding wolves to the Island.
“We were not able to document wolf reproduction on Isle Royale in 2014, and if that proves to be true, then there has been no reproductive success during three of the last four years,” said Peterson at the time.
Three wolves were documented March of 2015, but by February 2016, researches could only find two, a male and female, believed to be a father and daughter.
Over the last 70 years, an average of 22 wolves occupied the Island, with as many as 50 at one time.
With few predators, the moose population exploded and is today estimated to be 2,060.
National Park Service (NPS) plans
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 a decision to—or not to—bring more wolves to the Island.
Before reaching a decision, the NPS looked at a variety of alternatives for the management of moose, wolves, and vegetation on the big island. The moose-wolf-vegetation food web is tightly coupled, and the park’s final plan to reintroduce wolves takes into account those relationships.
Climate change 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 15 years 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 make sure there was genetic diversity, wolves were captured and moved from Canada, Minnesota, and Michigan to the Island. Today there are seven males and eight females, with one original wolf left.
Tracking the wolves are NPS and research partners from the State University of New York – College of Environmental Science and Forestry. They are using data gathered from GPS collars on new wolves to monitor associations between individuals and identify possible pack formation. As anticipated, new wolves immediately began interacting with each other. Researchers confirmed that introduced wolves were feeding, traveling, sleeping in proximity to each other, and forming groups.
Two or more wolves traveling and feeding together characterize Wolf “groups.” A “pack” is groups of two or more wolves traveling together and defending a territory, and also if a breeding pair reproduces.
Individual preferences for mating and group or pack formation can be quite variable for a social animal like the wolf. Mate selection and pair bond formation can occur at any time, but wolves only breed and produce pups once per year. Consequently, pack formation can take time. Based on these definitions, there are currently no wolf packs on Isle Royale.
Dr. Jerry Belant, Campfire Conservation Fund professor at SUNY-ESF and project collaborator, added, “Wolves are a highly social species, and we continue to monitor their movements to document groups, and ultimately pack formations as demonstrated by reproduction.”
Mortality events
This fall, two wolf mortality events occurred. In September, researchers and NPS staff detected a mortality signal and recovered the remains of female W004F. Field evidence and subsequent necropsy at the U.S. Geological Survey National Wildlife Health Center in Madison, Wis., determined W004F died from wounds caused by another wolf or wolves.
In October, just before the park closing, NPS staff came across the remains of a male wolf, M183, one of the two remaining resident wolves inhabiting Isle Royale. Necropsy revealed that another wolf or wolves had also killed M183.
These events are not uncommon as wolves defend and establish their territories and social hierarchy. With many wolves on the Island sorting out their relationships with one another, the dynamic nature of wolf social organization, territoriality, and wolf-on-wolf aggression during group and pack formation is not unexpected.
“With the death of the island-born male, travel patterns of the remaining wolves are likely to change significantly, and are probably dependent on whether or not the island-born female is still alive, whether she is territorial and how she gets along with the newcomers, both males, and females. She is the final native wolf, never radio-collared, and searching for her will be a priority during the upcoming winter study,” commented Rolf Peterson.
This last summer, “location cluster investigations,” documented 122 instances of two or more wolves with overlapping space use. Twenty-nine cases (23.8 percent) of space use overlap were associated with prey remains and feeding behavior, 68 percent were associated with bed sites; wolf use for the remaining 7.4 percent of sites was unknown or could not be determined.
Researchers continue to monitor location data weekly for evidence of the three newest wolves, released on the island in September, who are adjusting to their new homes, interacting and forming associations. These wolves are interacting with each other (W017M and W018F were traveling together in late November) and with the wolves released last spring (W018F and W016M moved together in early November).
NPS and its collaborators will continue to monitor the interactions, group formation, and genetic diversity of new wolves over winter and spring to document breeding (January/February) and denning (April/May) activity in Isle Royale’s wolf population. Closely monitoring social organization will provide insights into the genetic health of the population. The NPS has partnered with Dr. Kristin Brzeski, wildlife geneticist at MTU, to sequence the Isle Royale wolf genome for long-term monitoring of genetic health of the population.
“We have a unique opportunity to look simultaneously at the past and future of Isle Royale wolves’ genetic health. With the death of M183, we can now more fully understand how genetic isolation and inbreeding impacted the historic wolf population and use that to better monitor the new founders. This is an exciting time, and we will be using cutting-edge genetic tools to track reproduction, inbreeding, and genetic change through time, hopefully providing a piece of the puzzle for maintaining a thriving Isle Royale wolf population,” said Brzeski.
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