One of Minnesota’s two distinct populations of the lumbering animals has dropped from about 4,000 to 100 since the 1990s.
The other population is down to fewer than 3,000 from 8,000 over the same period.
Wildlife experts say manmade climate change appears to be behind most of the declines.
They point to the increased number of winter ticks in New Hampshire that have thrived due to a longer fall and less snow on average.
“You can get 100,000 ticks on a moose,” state biologist Kristine Rines told The New York Times.
Brain worms and liver flukes, which thrive in moist environments, have ravaged the moose populations in Minnesota.
And the loss of forest cover in British Columbia due to an epidemic of pine bark beetles, which thrive in warmer weather, has left the moose exposed to hunters and other predators.
Since moose shape the landscape as they graze, even sometimes creating habitat for nesting birds, wildlife officials fear their loss could have a ripple effect through the environment.