Wildlife biologists at Voyageurs National Park recently completed an aerial survey of the park's moose population in February-March 2015. The 2015 population estimate for the Kabetogama Peninsula was 46 moose, similar to estimates of 40-51 moose from 2009 to 2014. The Kabetogama Peninsula is a 118-square mile roadless wilderness area that contains almost all of the park’s moose population.
Similar to 2014, park staff observed few calves in 2015 and no sets of twins. The estimated calf:cow ratio was 0.38 and calves were 14% of the population. The bull:cow ratio observed during the 2015 survey (1.0) was higher than in previous years, but is likely a reflection of our sampling protocol rather than an actual change in the adult sex ratio over the last year.
The continued apparent stability of the low-density population in Voyageurs is corroborated through ongoing monitoring of GPS-collared moose. None of the 10 collared adult moose have died since the last aerial survey was completed in 2014. Three additional collared moose survived at least 2-10 months until we lost contact with their collars. Overall, mean annual mortality of adult moose in Voyageurs National Park has been 7% since monitoring began in 2010. By comparison, annual mortality of adult moose in the declining northeastern Minnesota moose population in recent years has been as high as 20%.
Voyageurs National Park is at the current southern extent of moose range in North America. Warmer annual and summer temperatures may be stressing moose populations in the region. The moose population declined by more than 60% between 2006-2015 in northeastern Minnesota and several areas in adjacent Ontario have also documented recent declines.
There are likely multiple factors involved in the observed declines including climate-related stresses on health and reproductive status, diseases and parasites, predation, and changes in habitat. Moose in Voyageurs experience all of these factors, including documented deaths from the fatal brainworm parasite and other health-related effects. However, wolf predation on adult moose appears to be uncommon. White-tailed deer and beavers are abundant in the park and wolves prefer to feed on these species rather than moose.