DETROIT (AP) — The moose population in Michigan's Upper Peninsula is growing more slowly than before, possibly because of conditions related to a warming climate, scientists say.

The Detroit News reported that moose numbers grew at a rate of 10 percent annually between 1997 and 2007. The increase has dropped since then to 2 percent, for an estimated total of 451 moose this year.

"As temperatures have increased, we're seeing some association with these declining populations," said Dean Beyer Jr., a wildlife research biologist with the Michigan Department of Natural Resources.

Moose are struggling more in some places than others. Minnesota canceled its hunting season for the iconic symbol of the north woods because the population had fallen 35 percent over the past year and 52 percent from 2010.

New England has a much larger moose population and the range there may be expanding, although numbers may be declining in some northeastern states. In North Dakota, the population appears to be holding its own or growing. But some Rocky Mountain states are experiencing declines. While Canada's moose population remains large, it's been falling across the border in Ontario.

Researchers are considering factors including disease and nutrition as possible explanations for declines.

One theory in Michigan is that rising temperatures have bolstered white-tailed deer, which carry parasites that are lethal to moose. Another possible culprit is loss of trees that often provide cover for the animals from natural predators.

Scientists have ruled out attacks from resurgent gray wolves as a significant contributor, Beyer said. The area of the northwestern Upper Peninsula where moose are concentrated has not drawn wolf packs thus far.

Officials imported moose to the area in the 1980s in hopes of boosting their presence. Their numbers have remained too low to allow a hunting season.