One population of moose in Montana dropped from 4,000 in the 1990s to less than 100 today. Another dipped 25 percent a year, down to 3,000 from 8,000.
A number of culprits seem to be at fault for sickening and killing the moose, but many of the causes seem to be a result of the warmer temperatures resulting from climate change.
Across the northern U.S. and Canada, shorter winters have led to the increase in parasites that can weaken moose.
Winter ticks in New Hampshire have thrived in the longer fall seasons with less snow. Unlike deer, which have evolved to groom the ticks off, moose don't groom.
“You can get 100,000 ticks on a moose,” said Kristine Rines, of the New Hampshire Fish and Game Department.
The ticks hatch in the fall, and infest the moose, where they remain dormant through the winter. When they begin feeding in January or February, the moose can lose so much blood it becomes anemic, while the itching drives the moose crazy, scratching and tearing off large chunks of hair, leaving it vulnerable to hypothermia in the cold spring rain.
Nor does the moose's habit of feeding in lakes wash away the ticks -- the insects form air bubbles that allow them to survive immersion and cling to their host.
Brain worms and liver flukes, two parasites that appear to be to blame for the moose deaths in Minnesota, rely on snails for part of their life cycles. The parasites' snail hosts have flourished as the warm, moist seasons have grown longer.
And in British Columbia's Cariboo Mountains, an epidemic of pine bark beetles, blamed partially on warmer weather, killed off the forests in which the moose lived, leaving them vulnerable to predators and hunters.
“It’s complicated because there’s so many pieces of this puzzle that could be impacted by climate change,” said Erika Butler,a former wildlife veterinarian at the Minnesota Department of Natural Resources.
Unregulated hunting, as well as wolves, could also be to blame. Minnesota wildlife officials have suspended all moose hunting permits, while Montana has cut theirs in half.
Researchers are hoping a $1.2 million study, which will help track moose and know instantly when they die, will help increase understanding into moose deaths. Because the animals have high levels of body fat, they decompose rapidly, so it is critical to complete a necropsy within 24 hours.
Trackers, along with sensors that monitor heart rate and temperature, will help researchers reach a moose in time to learn from its death.
“If the heart stops beating, it sends a text message to our phone that says, ‘I’m dead at x and y coordinates,’" said Butler, who is leading the study. Then her team can rush to the location by car or helicopter.
That kind urgency may seem like overkill, but for the moose, and for the ecosystems that depend on it, scientists can only hope it isn't too late.