Alces alces, the moose, is found in both the Western and Eastern halves of Michigan’s Upper Peninsula and can be seen roaming in a number of MNA’s sanctuaries in the area. This is the second installment of the moose series focusing on the health and population of moose in Michigan’s Upper Peninsula.
The population of moose in the U.P. has a complicated history. There are two populations that tend to be discussed separately: the Eastern U.P. population (which is discussed in another blog post ) and a population of about 420 animals in the Western U.P. counties of Marquette, Baraga, and northern Iron. Western U.P. moose populations were replenished through a relocation project done by the Michigan Department of Natural Resources (DNR) in the 1980s and have been the subject of many studies since then.
Moose in the Western U.P. were transferred there by the DNR from Algonquin Provincial Park in Ontario, Canada in 1985 and 1987. There were 59 animals were released in Marquette County, north of Van Riper State Park. The goal was to have 1000 animals by the year 2000 and while that number was not achieved, the herd has slowly increased its numbers and its range. According to Dean Beyer, wildlife research biologist for the Department of Natural Resources and the Environment (DNRE), that goal would have required highly optimistic rates of reproduction.
The reproduction rates of the Western U.P. moose tend to be about 70 percent, which means 70 percent of female adults reproduce in a given year. This is lower than the average North American rates, which are about 84 percent. The Upper Peninsula’s calf survival rates are very good, Beyer said, because other populations, like those in Alaska or Canada, have more natural predators. The adult survival rates are also lower than the North American average, but are consistent, about 86 to 87.
Why are factors, such as the reproduction rate, lower in the Upper Peninsula then in other areas of North America? A number of factors could be limiting the population in the U.P, including the temperatures in the Upper Peninsula, Beyer said. The U.P. is at the southern edge of the moose’s range and warm temperatures during the summer may limit its normal activity. Moose are built for cold weather and it is difficult for them to lose body heat
“Warmer temperatures are probably affecting moose in a variety of ways,” Beyer said. “They could change the dynamics with the parasites they suffer from, like liver flukes and brainworm. They could also cause them to forage less during the summer heat, which would affect their health.”
An example of a moose population that has probably been affected by temperatures is in nearby northwestern Minnesota. In the mid 80’s the area had around 4000 moose, but the latest survey put the number at fewer than 100. Officials are trying to figure out the cause of the drop in population, but warmer temperatures are a definite possibility, Beyer said.
“Some climate change projection models show that by the end of the century the Upper Peninsula’s summers will be more similar to Missouri’s summers,” Beyer said, “and the Upper Peninsula’s winters more similar to southern Lower Peninsula winters. If that actually happens, then it is likely the southern edge of the moose’s range will move north.”
Another reason for a limited moose population is mineral deficiencies in some areas of the Upper Peninsula, according to DNRE Wildlife Biologist Terry McFadden. The moose may be staying in areas with the proper combination of minerals to sustain them. Beyer said moose have been found with low levels of selenium, a mineral that is important for cell wall maintenance. When livestock are low in selenium it can result in poor viability for young or sterilization in adults. While low levels of the mineral have been found, Beyer said the DNRE couldn’t find evidence to support selenium as a factor in population limitation, but it is possible.
Despite these dire predictions for the moose in Northern Michigan, Beyer said, the U.P.’s population has been slowly, but steadily, growing at about five percent to 10 percent a year. Why is the population of moose in the U.P. seemingly less affected by warmer temperatures than those in Minnesota? The answer could be in the slight protection offered by Lake Superior, which helps maintain a climate more livable for these creatures.