PORTLAND (AP) – New England’s moose population is under siege from tiny ticks that have become so numerous in recent years that biologists are concerned about the long-term effect on the ungainly mammals.

Winter ticks, as they are known, appear to be more plentiful in the North Woods because of high densities of moose and deer and a general trend toward shorter winters, with last winter being an exception, biologists say.

“These ticks have always been around, but with recent changes in climate in the last decade or so, everyone across the southern edge of the (moose’s) range is seeing this phenomenon, and Maine, with the largest herd in the lower 48 states, has a lot of loss,” said Mark McCollough, a biologist with the U.S. Fish and Wildlife Service in Old Town.

The ticks, which are smaller than deer ticks and wood ticks, cluster together in large numbers each fall on large mammals such as moose, deer, cows and horses. In April, the female ticks fall off the animals; if they reach bare ground instead of snow, they lay thousands of eggs.

A recent New Hampshire study found that the average moose carries about 35,000 ticks but can have as many as 160,000, or about 50 per square inch of hide, in heavy years.

The ticks can suck out so much blood that they leave moose anemic and emaciated, unable to survive winter. To get rid of the ticks, infested moose rub on trees and often scrape away their dark winter coats – becoming so-called “ghost moose” in spring.

In 1992, an estimated 20 percent of New Hampshire’s moose herd had at least some hair scraped off because of ticks. Close to 100 percent do now, said Kristine Rines, moose project leader for the New Hampshire Department of Fish and Game.

The ticks take the hardest toll on moose going through their first winter without the fat and protein reserves of adults.

In the worst of years, New Hampshire’s north country has lost close to 70 percent of its calf crop to winter ticks and about 20 percent of the adults, Rines said. Ticks may be keeping the state’s herd size at about 6,000.

“The population has not grown at the rate that we would expect,” she said.

Maine, which has an estimated 29,000 moose, has not studied the phenomenon. But its moose herd is clearly affected, said Lee Kantar, a biologist with the Maine Department of Inland Fisheries and Wildlife.

“We don’t know the extent to which it’s causing additional mortalities. We know it’s a big factor,” said Kantar. “That’s something we’d like to look at more closely.”

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