Wolves and moose on Isle Royale
The single predator-single prey relationship between wolves and moose on Isle Royale in Lake Superior is unique, and has been the subject of detailed study for over 55 years. Isle Royale, the principal island of Isle Royale National Park in Michigan in the United States, is an isolated island with little of animals into and out of the island and as a national park human interaction and impact on the two species is also limited. Both the wolves and the moose first became established populations on Isle Royale in the 1900s. Over the fifty years of the study, the populations of both moose and wolves have shown repeated spikes and declines and have not settled to a balanced relationship. The moose populations have ranged from 500 to 2500 while the number of wolves has ranged from almost 50 down to 2.
The relationship between wolves and moose on Isle Royale has been the subject of the longest research study of its type, begun in 1958. The wolves have been subject to inbreeding and carry a spinal deformity. As of the 2014 count, there were only 9 wolves on the island, with the 2015–2017 counts showing only 2. A review completed in 2014 determined that new wolves would not be introduced into the park to attempt a genetic rescue, but as of December 2016, the National Park Service had instead decided to introduce 20 to 30 wolves to the island.
Isle Royale National Park is made up of about 400 islands, and is in the northwest portion of Lake Superior. It is about 50 miles (80 km) from Michigan's shore, and 12 miles (19 km) from the Canadian shore. The main island is about 45 miles (72 km) long, and nine miles (14 km) wide at the widest point, with an area of 205 square miles (530 km2). There are no roads, and no motorized vehicles are allowed on the island. The park is closed from September to May during which the wolf-moose study personnel are the only humans resident on the island.
As an isolated island, Isle Royale initially had neither wolves nor moose. The moose are believed to have either swam across Lake Superior from Minnesota in the early 1900s or were stocked on the island by man for the purpose of recreational hunting. In 1949 a pair of wolves crossed an ice bridge from Ontario to the island during a harsh winter. But because only one pair of wolves migrated to the island, they have suffered from severe inbreeding. According to Rolf Peterson, a professor at Michigan Technological University and the lead wolf-moose researcher, "Moose were isolated here 100 years ago. Most of the genes are still here, but they have enough population (to compensate). There are so few wolves that they have lost genetic variability. The scientific dogma suggests that they are not going to make it." In fact, all of the wolves' DNA on Isle Royale can be traced back to one ancestor. Inbreeding leads to mutations and fitness problems, often accompanied by violent social rejection by other wolves.
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