After 60 years, Isle Royale continues world's longest predator-prey study

May 17, 2018

Researchers from Michigan Technological University have released the annual Winter Study report detailing updates on the ecology of Isle Royale National Park. For the third year in a row, the Isle Royale wolf population remains a mere two, while the moose population continues to stay above the historic average. Without the pressure of predation, the expanding moose population will have a greater impact on the island's forest ecology.

The study co-authors include Research Professor Rolf Peterson, Professor John Vucetich and Assistant Research Professor Sarah Hoy. They say the heart of the study's success has been the more than 1,000 citizen science volunteers who have bolstered the study's fieldwork efforts in small teams totaling about 40 people each year for the last 30 years. Together, they helped gather enough skulls to document the shrinking moose of Isle Royale, observe seasonal wolf activity and earned more than their fair share of hiking boot blisters.

In terms of population trends, little changed on the island this past year. As Peterson, Vucetich and Hoy write in the report about the last male-female pair of wolves, "there was no evidence of any change in their status, except they are older by a year."

The pair are closely related--both as siblings and as father-daughter--and the inbreeding within the island's isolated wolf population is what contributed to their demise. The wolves' numbers started plummeting in 2009, declining by 88 percent from 24 to 2 wolves for that period; historical levels of wolves typically varied between 18 and 27. The pair, aged eight and ten years old, may have produced a pup several years ago but the female has continued to reject the male as a mate.

One meager hope for new wolves formed briefly in early February. For almost a week, an ice bridge connected the island to the Ontario mainland. However, the ice conditions were rough, the bridge did not last long, and the researchers found no evidence of wolves crossing over. With fewer ice bridges and warmer winters, the chances of wolves recovering naturally is slim to none.

As the wolf population declined and forage remained abundant, the moose population has been able to expand. Counting conditions for the past two winters have not been ideal, but the team estimates the moose population to be around 1,475 members. The population usually numbers between 700 and 1,200 moose. Hoy, who led the skull size study of the island's moose that found their size decreased by 16 percent over 40 years, says we are observing a population in transition.

"Although the effects on body size are quite subtle, there was a marked decline in lifespan over the study period," she says, explaining that wolves are not the only factor affecting moose. The changes in both populations impact the rest of the island, particularly balsam fir, which is a staple winter food for moose. "Maybe the trees can withstand one major source of stress, but with the lack of predation and a changing climate, can it withstand two or more?"

Peterson, who has been a part of the Isle Royale research for the past 50 years, says the island is a unique place to study moose and wolves. Unlike big, complex spaces like Yellowstone, where the cascading effects of wolf populations are still debated among scientists, Isle Royale is a neatly contained ecosystem that can provide insight into other Northwoods settings.

"This is the perfect environment to observe predator-prey interactions--but doesn't make it easy," he says. "We anticipate big things are about to happen, with wolf predation restored, that will once again change the direction of the island's ecosystem. It might take a long time to see the full impact of those changes."

The National Park Service has proposed introducing 20-30 wolves to the island over the next three years. The final environmental impact statement was completed and the identified preferred alternative is to restore wolf predation, but the final decision on the plan is pending as of the Winter Study report publication.
-end-


Michigan Technological University

Related Wolves Articles from Brightsurf:

Wolves alter wetland creation and recolonization by killing ecosystem engineers
Researchers observed and demonstrated that wolves affect wetland ecosystems by killing beavers leaving their colonies to create new ponds.

Trump administration delists gray wolves: Response from the experts
The BioScience Talks podcast (http://bioscienceaibs.libsyn.com) features discussions of topical issues related to the biological sciences.

Swedish, Finnish and Russian wolves closely related
The Scandinavian wolf originally came from Finland and Russia, and unlike many other European wolf populations its genetic constitution is virtually free from dog admixture.

Wolves attached - Adult wolves miss their human handler in separation similar to dogs
One key feature of the dog's success is that they show attachment towards their owners.

Comparing the controllability of young hand-raised wolves and dogs
During domestication, dogs most probably have been selected for increased tractability.

Positive YouTube videos of wolves linked to greater tolerance
A new study from North Carolina State University suggests that people have more tolerance for wolves after seeing positive videos about them, which could make YouTube an important wolf conservation tool.

Dogs and wolves are both good at cooperating
A team of researchers have found that dogs and wolves are equally good at cooperating with partners to obtain a reward.

'Wolves in sheep's clothing' -- the superbugs outsmarting laboratory tests
Hospital screening tests are failing to identify the true extent of microbial resistance, according to new research.

What wolves' teeth reveal about their lives
UCLA biologist discovers what wolves' broken teeth reveal about their lives.

Fearing cougars more than wolves, Yellowstone elk manage threats from both predators
Wolves are charismatic, conspicuous, and easy to single out as the top predator affecting populations of elk, deer, and other prey animals.

Read More: Wolves News and Wolves Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.