While the moose population at Isle Royale National Park in Michigan is estimated at 1,300 animals, up from just 540 in 2005, the island's wolf population stands at just two, according to a winter survey of the park by Michigan Tech University researchers.

"The 2016 Winter Study observed the tracks of two wolves on the island, down one wolf from the previous year," a park release said. "The two remaining wolves are believed to be animals that share a common mother and the remaining female is the daughter of the remaining male, suggesting significant impediments to reproductive success. These wolves are estimated to be 6 and 8 years old, respectively."

Chronic inbreeding appears to have impacted the health of the wolf population. There was hope that "ice bridges" that formed between the Lake Superior island and the Canadian mainland during the winter of 2013-14 would enable wolves to arrive from Canada with new genes. But no new wolves reached the island, while one female left and was killed by a gunshot wound in February 2014 near Grand Portage National Monument in Minnesota.

Isle Royale wolves have been in decline for more than a decade. In recent years park managers have discussed island and wolf management with wildlife managers and geneticists from across the United States and Canada and have received input during public meetings and from Native American tribes of the area. Those discussions have examined the question of whether wolves should be physically transported to Isle Royale, in large part due to concerns that a loss of the predators would lead to a boom in the moose population that likely would over-browse island vegetation.

Park officials currently are preparing an environmental impact study on whether to physically bring wolves to the island in a bid to rebuild the population and its genetic diversity.

Moose, meanwhile, have undergone population swings in recent years, shifts that biologists attribute to "changes in forest type, weather severity, disease, and changes in predation pressure."

"The moose population was at an all-time low in 2005 with 540 animals. MTU scientists concluded that the declines were likely associated with 'Climate warming and increased ticks…' which in turn were thought to result in low levels of moose recruitment (birthrates)," the park's release said. "Forest succession might also explain some of the decline.”

Since that time, however, the moose population has boomed to an estimated 1,300 this year (+/-390 individuals).  

"Dr. Rolf Peterson was able to note a higher percentage of twin calves in this year’s study, predicting that it may bolster the population," the release added. "Twins are normally a result of moose being well nourished and exposed to limited predation stresses. The survey data on moose shows that the population is still on the increase; however, this is a different trend than what is being found in Minnesota and suggests that there could be differing factors impacting moose at the park than on the mainland."

Also of note from the past winter's survey was that the island's tick infestation has declined since peaking in 2007.

"Tick abundance fluctuates with weather conditions, and declines were observed with the cold, long-lasting winters of 2013 through 2015," the park release said.