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 since 1958.

[4] The relationship between wolves and moose on Isle Royale has been the subject of the longest predator-prey research study, begun in 1958.

[11] Isle Royale National Park is made up of about 400 islands, and is in the northwest portion of Lake Superior.

The moose are believed to have either swum across Lake Superior from Minnesota in the early 1900s or were stocked on the island by humans for the purpose of recreational hunting.

[13] In 1949 a few wolves, possibly only a single pair, crossed an ice bridge from Ontario to the island during a harsh winter.

According to Rolf Peterson, a professor at Michigan Technological University and the lead wolf-moose researcher, "Moose were isolated here 100 years ago.

[18] Because balsam fir does not give sufficient moisture, moose have recently been spotted eating snow, a very rare occurrence.

[19] Moose mostly die from the consequences of malnutrition: they become emaciated and slowed down by arthritis, until they are easy prey for a wolf pack.

[17] Moose make up nine-tenths of an Isle Royale wolf's diet (the remainder being snowshoe hare and beaver).

[23] In early 1997, a particularly virile male wolf that had not been born on Isle Royale was observed by researchers on the island.

This was the first time that an adult wolf had entered the island's isolated population since the study began, and he is assumed to have crossed over the ice from mainland Ontario, 15 miles away.

[24] Furthermore, Old Gray Guy's offspring soon began breeding with one another, leading a new set of traits to become reinforced by heavy inbreeding.

[25] A 2023 study found that Old Gray Guy's impact on the gene pool had been partially reversed as his inbred descendants died without offspring.

Absent a new infusion of migrant wolves, or human intervention, the original situation of a high moose population limited only by starvation is the prospect.

[28] In December 2016, the National Park Service (NPS) put forward a plan in which they would add 20 to 30 wolves to the island in order to prevent the pack from disappearing completely.

[29] In December 2017, Sarah Hoy et al. of Michigan Technological University published results of a 40-year study showing a decrease in the size and lifespans of moose.

[30][31] In March 2018, with the release of the final Environmental Impact Statement, the NPS formally proposed to relocate 20 to 30 wolves to the island over a three-year time period, starting immediately.

[11] Over the following months the newly introduced male wolf died and one of the females left the island via an ice bridge.

Beavers have been exposed to predation by having to travel long distances to find the only parts of the island where aspen remains.

Since El Niño hit in 1998, the climate has warmed up, which has significantly affected the moose population across North America.

[41] Ticks are more prominent in years where spring arrives earlier than usual, because when they fall on ground not covered in snow, then they can reproduce.

Hot summers also lead to moose resting in the shade, or in the water to keep cool, making them easier prey for wolves.

Not only has the recent warming of Isle Royale hurt the moose, but completely opposite problems harm them also.

This also causes trouble for moose that are born in the winter, because they can no longer swim across the water to another island, and must raise the new calf in the snow.

[15] In 1958, as a graduate student at Purdue University, L. David Mech began studying the wolves of Isle Royale.