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CONWAY, Mass (Reuters) - Moose living in northern states such as New Hampshire and Minnesota face an increased threat from blood-feeding ticks and deer-borne parasites because of shorter winters caused by climate change, U.S. wildlife officials say.
Winter ticks account for 41 percent of all deaths of the antlered animal popular with hunters and wildlife watchers in New Hampshire -- the same percentage killed there by hunting and moose-vehicle collisions, according to a study released this week by the state's Fish and Game Department.
Nearly all of the calf deaths noted during the study, which began collaring and tracking moose in 2001, were caused by winter ticks, said Kristine Rines, the department's moose project leader.
Moose, which in New Hampshire average six feet tall at the shoulder and weigh 1,000 pounds, tend to become infested with an astounding number of ticks at one time.
One animal typically can get 30,000 ticks in normal fall weather conditions, but as many as 160,000 ticks during winter in years with a late first snowfall, researchers said.
Often the eventual result for moose is malnutrition and death.
Moose are at a physiological low when winter ticks are feeding, leading to stresses like reduced blood volume, a thinner coat due to scratching, and an inability to lie down and rest.
"This combination leaves the moose open to an array of other infections," said Rines.
She said a high number of ticks is "almost a death sentence" for calves because they can lose their entire blood supply over just a few months.
Climate change magnifies the tick problem because the pests live longer and reproduce in greater numbers if there's less snow on the ground by spring.
The situation may only get worse, according to a recent Union of Concerned Scientists report that shows climate change could prompt New Hampshire's snow season to shrink by 50 percent by mid-century.
"Rising temperatures over the past few decades have caused snow to become wetter and decreased the average number of snow-covered days across the state," the scientists' climate report said.
New Hampshire is not unique in seeing rising temperatures take a toll on moose. Biologists in Minnesota say the warming trend is at least partly to blame for the sharp drop in moose numbers in the state's northwestern areas since the early 1990s.
Researchers in New Hampshire will spend the next several years studying the best way to accurately determine the numbers of ticks on moose and how that relates to mortality rates, as well as the changing climate, the study said.
Editing by Colleen Jenkins and Jerry Norton