Other types of ticks, such as wood ticks and deer ticks, grab a bite and drop off. Winter ticks are much greedier. They hang on for the entire winter, fattening up on blood until their bloated hides resemble a watermelon. Some moose, especially small calves, develop anemia and eventually starve. In a vain attempt to dislodge ticks, adult moose scratch until the brown layer of their fur gives way to a thin grey layer underneath. They’re called Ghost Moose, because that’s how they look.
As the climate in the two states warmed over the 20th century, and the duration of summer weather increased by up to two weeks, and the snow that kills winter ticks fell less or melted faster, their populations grew, scientists say. When conditions in the states are cold, females that leap off moose in April to lay eggs fall on heavy snow pack that kill both. But more of the eggs are now surviving to hatch in fall. A single female lays 3,000 eggs the size of salt crystals.
New Hampshire and Maine are entering the third year of a study to show the impact of winter ticks on moose populations, said Lee Kantar, a moose biologist for the state of Maine. “The first two years we had rather moderate to high calf losses, and the first year we had some adult losses,” Kantar said. “The second year we had very little adult loss.” That was based on one study area in western Maine. The results, Kantar said, are far from conclusive, and overall moose populations in both states are still robust.
“This year we’re studying an area in northern Maine,” he said. “I think my concern is that while we know the winter tick has a critical role with moose, we don’t know what that ultimately means. We’re trying to understand the complexity of the issue right now. A population of animals like moose has to be looked at in more than one year. We have to be guided by science and be able to quantify these rates.”
Scientists are fairly sure that there are more than enough winter ticks to go around. Conditions over the past few years have been almost perfect for population booms. “Overall, we’ve seen a general decrease in snowfall over the past several decades,” said Mary Stampone, a New Hampshire state climatologist and associate professor of geology at the University of New Hampshire.
Quoting the Environmental Protection Agency’s Climate Change Indicator in the United States, Stampone said some locations in the Northeast are seeing a reduction in precipitation falling as snow. “We’re getting precipitation but more of it is falling as liquid,” she said. There is wide variation from year to year, she said, but in general, there are “fewer days and less depth of snow on the ground.” Maine’s weather stations track snow depth and measurable snow pack is recorded on fewer days. “Maybe there’s less snowfall or it was warmer and more snow melted,” Stampone said.
During the 20th century, Maine warmed by 3 degrees Fahrenheit, and “the warm season increased by two weeks,” according to Maine’s Climate Future, a 2015 update produced by the University of Maine. “Global climate models predict that the warm season will increase by an additional two weeks over the next 50 years,” the update said. “Winter is warming at a faster rate than summer.”
As Maine’s summers become warmer and longer, the number of excessively hot and humid, days when heat indices rise above 95 degrees are likely to increase, according to the update. “Most places in Maine currently see fewer than four such high heat days on average in a given year, but by 2050 some locations could see ten or more.”
In 2013, the Manomet Center for Conservation Sciences and state climate change working group reported that two-thirds of Maine’s plant and animal species are vulnerable to the change. “Vulnerable species include Maine icons like moose, which are vulnerable to heat stress and ticks that survive through mild winters,” the update said.
Winter ticks aren’t individually scattered over the bodies of their hosts. They feed in big groups, like clumps of grapes on a sprawling vine, ballooning until an animal that was the size of a speck is as big as a cough drop. Moose become so stressed from hundreds of thousands of tiny bites every minute and every day that they can’t eat even if food is handed to them.
“They look terrible. Their body weights are down. They have secondary skin infections from multiple bites,” Kristine Rines, a New Hampshire moose biologist said when the study started two years ago. They lose so much fur that they freeze whenever the weather manages to turn cold.
“In the central and White Mountain portion of the state where winters are short, we’ve seen a steady decline over the past five to seven years,” Rines said. The state’s moose population is about 4,500, at least 3,000 fewer than five years ago. New Hampshire Fish and Game’s Wildlife Journal magazine wrote about the moose die-off from tick infestation in 2011 under the headline “Ghost in the Woods.” Moose-watching tours generate $115 million yearly in New Hampshire, but operators say current tours last hours longer than in past years as they seek to spot a single moose.
Kantar called the winter tick an “insidious” parasite. “This is the time of year they are waiting to ambush a moose,” he said. When a moose passes a stalk where thousands of them are waiting, it seems to bloom to life as they reach and grab a hair. “If it’s windy or rainy or cold, those ticks are going to die. But if the conditions are good and the ticks are waiting, thousands on a stick …” Kantar paused, suggesting that hardship and possibly death for the moose was inevitable.
“The conditions right now and into November are critical,” he said. “The tick is questing to find a host.”
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