Moose Die-off Mystifies Researchers

Moose populations across North America are plummeting, and no know knows why.

Minnesota's strongest population declined by 35 percent between 2012 to 2013, with the current 2,760 representing a 70 percent drop since 2006. New Hampshire's population has fallen from roughly 7,000 to closer to 4,600, and Jackson Hole, Wyo. is down to less than 1,000, in contrast to the state goal of 3,600 animals. Meanwhile, declines in Montana have led to a 40 percent reduction in available hunting tags between 1995 and 2010.

According to the Wildlife Management Institute, the only place that has shown a growing population of moose is Maine. A recent aerial study estimated more than 75,000 animals call the state home, the majority dwelling in the more isolated northern stretches of the state.

"There has definitely been a change. Something has been going on and we've seen it in the hunter success rates, the amount of effort required to fill a tag and in what hunters report seeing while in the field," said Justin Gude, Wildlife Research & Technical Services Bureau Chief with Montana Fish, Wildlife and Parks. "But the one thing that is very clear is that there is not enough information -- we don't have substantial evidence of a long term decline, but we need to figure out what is going on."

One possible culprit is an apparent rise in winter tick infestations. Ticks thrive in years with lower snowpack levels and early snow melt, with as many as 150,000 latching onto a single moose. Not only do moose become anemic when this happens, but they often are left with patchy, thinning coats as they rub against tree trunks and other surfaces in an effort to rid themselves of the pests.

Brain worm, a common parasite in white tailed deer, could also be contributing to the decline, according to Kris Rines, New Hampshire Fish and Game's moose project leader, noting that research suggests that areas with higher deer densities often are unable to support a moose population.

In the Rocky Mountains and Upper Midwest, some blame the moose's decline on the increase in wolf populations, while others throughout the United States suggest habitat changes likely play a role. In Maine where the moose is thriving, the spruce-fir forests that the animal prefers are managed for commercial timber harvest, allowing for plenty of forage, reports Lee Kantar, a deer and moose specialist from the Maine Department of Inland Fisheries.

Regardless of the reason behind population declines, scientists all agree on one thing: more information is needed before any conclusions can be drawn.