An insidious pest is killing about 70 percent of moose calves across Maine and New Hampshire, and their deadly work is being aided by warming temperatures and shorter winters that allow the parasites to survive longer, scientists believe.
They are winter ticks, which attach themselves to a single moose by the tens of thousands. Adult females can expand to the size of a grape and engorge themselves with up to four milliliters of blood.
“The moose are being literally drained of blood. This is about as disgusting as it gets out there,” said Pete Pekins, chairman of the Natural Resources Department at the University of New Hampshire.
Pekins and UNH are at the center of the largest study of New England moose ever conducted, a three-state effort stretching across the woods of Maine, New Hampshire, and Vermont in which researchers are attaching tracking devices to the moose as part of an effort to learn how ticks are affecting them.
If the reduction continues, researchers said, the range of New England moose is likely to shrink northward. And for many moose that survive, the ravages of winter ticks could render them less healthy and less likely to reproduce.
“It’s like a sinister, evil horror movie,” said Lee Kantar, the Maine state moose biologist.
Maine and New Hampshire teams recently captured a total of 123 moose cows and calves, attaching GPS and other electronic gear. In Vermont, which joined the program this year and began capturing moose Tuesday, the plan is to collar 60 animals.
The effort is a mixture of high tech and high drama as a helicopter swoops within 20 feet of a moose and fires an entangling net. The crew lands and then hobbles and blindfolds the animal, which researchers said has a calming effect, before collaring the moose and collecting the samples.
The drug-free process takes 10 to 15 minutes.
About 76,000 moose roamed Maine in 2012, said Kandar, who did not have a current estimate. New Hampshire has about 4,000, down from a peak of about 7,500 in the early 2000s.
And Vermont is down to 2,200, from a high of 5,000 animals in 2006, although much of that reduction was the deliberate result of hunting to bring the population into better balance with the habitat.
Now, the primary concern is winter ticks, which lie in wait on vegetation in the autumn — interlocked by the hundreds and thousands — until they attach themselves to a passing animal such as a moose.
Deer and other animals groom the ticks from their bodies. But for moose, which have not developed that ability, the insects become blood-sucking hitchhikers whose victims usually die in late winter and early spring.
“They’ll be on the moose in such large amounts, that the moose will literally scratch against trees and take the skin off,” said Wayne Derby, a master guide from Bethlehem, N.H. “Sometimes you’ll see 2 to 2½ square feet on the shoulders where the moose have rubbed off the fur.”
Derby has a term for the tick-infested animals: ghost moose.
If winter starts even two weeks late, that extra time in the forest means that more ticks — which do not fare as well in the snow — will find more moose to ride.
“Climate change is having an effect,” said Kent Gustafson, wildlife program supervisor for the New Hampshire Fish and Game Department. “We’ve seen winters basically get shorter over the last two decades or so.”
None of the researchers said New England is on a path to losing its entire moose population — Maine has more of the animals than the other lower 47 states combined — but the trend became worrisome enough to prompt the unprecedented study.
New Hampshire and Maine are in the fourth year of a project to collar hundreds of animals with tracking devices and collect ticks, hair, blood, and fecal samples from them.
Necropsies are often conducted later when they die, and the results are shared among the states to broaden the region’s understanding of why the population of one of the North Country’s iconic animals is declining.
Even with the drop, far more moose live in New England now compared with a century ago. Only 50 moose were estimated to be living in New Hampshire in 1950. But they rebounded across the region as pastures returned to forest, hunting declined, and a bounty of food became available when woodlands were churned up to fight spruce budworm disease in the 1970s and 1980s.
Now, moose also can be found in Massachusetts and parts of Connecticut, as well as throughout the three northern New England states. As the numbers of moose shrink again, scientists and state officials are not sitting on the sideline.
In New Hampshire, the study has focused north and east of the highest peaks of the White Mountains. And in Vermont, researchers are working in the northeast forests.
Pekins said the thinning numbers eventually might stem further decline. Fewer moose would mean fewer targets for winter ticks, which could lead to a reduction in their own population.
For now, however, the future for New England moose is shifting.
“As humans, we want everything to be in tidy, neat packages,” said Derby, the New Hampshire guide. “But nature’s not like that.”
Brian MacQuarrie can be reached at firstname.lastname@example.org.