Study: Ticks Kill Majority of Baby Moose

Concord Monitor

The news isn’t getting any better for New Hampshire’s moose, as the population explosion of winter ticks driven by warmer winters continues to take a toll.

An updated study by researchers at the University of New Hampshire has found that winter ticks, the parasite that has been killing moose throughout Northern New England for years, are the primary cause of an unprecedented 70 percent death rate of calves over a three-year period.

A main reason is that shorter, weaker winters are making it easier for the ticks to thrive.

“The iconic moose is rapidly becoming the new poster child for climate change in parts of the Northeast,” said Pete Pekins, professor of wildlife ecology. “Normally anything over a 50 percent death rate would concern us. At 70 percent, we are looking at a real problem in the moose population.”

In the study, published in the Canadian Journal of Zoology, researchers outline the screening of 179 radio-marked moose calves ages 9 to 10 months for physical condition and parasites from 2014 to 2016. They tracked new calves for four months each winter and found that a total of 125 calves died over the three-year period. A high infestation of winter ticks was found on each calf (an average of 47,371 per moose) causing emaciation and severe metabolic imbalance from blood loss, which was the primary cause of death.

Most adult moose survived but still were severely compromised. They were thin and anemic from losing so much blood. The ticks appear to be harming reproductive health, so moose are breeding less.

The researchers say winter tick epidemics typically last one to two years. But five of the last 10 years has shown a rare frequency of tick infestations which reflects the influence of climate change. They point out that right now these issues mostly are appearing in southern moose populations, but as climate change progresses they anticipate this issue to reach farther north.

“We’re sitting on a powder keg,” Pekins said. “The changing environmental conditions associated with climate change are increasing and are favorable for winter ticks, specifically later-starting winters that lengthen the autumnal questing period for ticks.”

Fall is considered “questing” season for winter ticks. They climb up vegetation and look to attach to a host. Once they attach, they go through three active life stages (larvae, nymph and adult) by taking a blood meal and feeding on the same animal. The ticks will feed and remain on one host during their subsequent molts until spring when adult females detach and drop to the ground. Their preferred hosts are moose and other mammals, including deer, elk, caribou and occasionally horses and cattle. Winter ticks rarely bite and feed on humans.

Co-authors of the study include UNH’s Henry Jones and Daniel Ellingwood, Lee Kantar and Matthew O’Neal of the Maine Department of Inland Fisheries and Wildlife, Inga Sidor of New Hampshire Veterinary Diagnostic Laboratory at UNH, and Anne Lichtenwalner of the University of Maine Animal Health Laboratory.

Funding was provided through New Hampshire Fish and Game and Maine Inland Fisheries and Wildlife in cooperation with the U.S. Fish and Wildlife Service Division of Wildlife and Sportfish Restoration, UNH and the Safari Club International Foundation.