Started in 1958, scientists have been tracking the ebbing wolf population on Michigan’s Isle Royale, an island in Lake Superior. It is the principal island in Michigan’s Isle Royale National Park, getting its status on April 3, 1940.
Isle Royale is the largest Island in Lake Superior, a little over 45 miles in length and nine miles wide at its widest point. The Isle Royale National Park also includes 450 smaller islands. There are only 18 mammal species found on this unique island archipelago, compared to over 40 on the mainland.
A single predator-single prey study begins in 1958
Started in 1958 as a 10-year study on single prey-single predator relationships between wolves and moose, it instead evolved to include the impact of climate, the effects on genetic variability and disease in the two populations. The study has seen fluctuations in the populations of both mammals, and this has led to a greater understanding of the degree to which the carnivores control the system.
Moose swam over to the island from Michigan in the early 1900s. Then in the 1940s, the Canadian wolves walked across an ice bridge that had formed during a hard winter. The three wolves included a breeding pair and one smaller individual, believed to be an adolescent. By 1958, the ratio of wolves to moose made for an enticing study.
Over the past 50 years, the moose population on the island has fluctuated between 500 to 2,500 while the wolf population has ranged from nine to 50, never really a balanced relationship. Only in extremely cold winters, the ice bridge forms and with this event, the chance of new wolves joining the population on the island ensure new genes are being added.
But the last time this happened was in 1997 when one lone wolf joined the population. This lack of fresh genes has led to inbreeding and an accompanying genetic spinal disorder and high mortality rates among the predators. An ice bridge that formed in 2014 allowed for the escape of three of the wolves from the island.
Non-intervention and the future of the study
By the year 2000, inbreeding was taking its toll, and researchers Rolf Peterson and John Vucetich, ecologists at Michigan Technological University hoped to save the wolf population by bringing in new wolves whose dominant genes would mask the faulty genes, but the national park Service can be slow to move, and the time for genetic rescue passed.
A year ago the NPS made the decision to “study the proposal” submitted by Peterson and Vucetich. But after dealing with the problem of inbreeding at an up-close-and-personal level, Peterson says, “We have science coming out our ears and it wasn’t enough to carry the day against an entrenched bureaucracy with a culture of non-intervention.”
A bigger problem than the demise of the wolf population awaits researchers in the future. The moose population has jumped 22 percent, from 500 in 2011 to over 1,125 today. If the wolves disappear, the growing population of moose on the island will “nibble the Isle Royale landscape into a steppe dotted by spruce, the only type of tree there that the animals do not eat,” say the researchers.
In March of this year, the US National Science Foundation renewed the $90,000 grant for another five years. The focus will now be on the moose and vegetation and the impact created by the loss of predation by wolves. Peterson, who has been tracking the wolves on Isle Royale since 1971 says, “They can kick me out if they want, but I won’t walk away.”
