When Westin Nelson of Skagway became the first Alaska hunter on record to harvest a mule deer, he may have been doing the state a favor.

Mule deer, better known as inhabitants of the Rocky Mountain and Great Plains regions, have been expanding their range northward, including into Alaska. As they do so, they are expanding the risks of parasites and some contagious diseases.

The most concerning issue is the winter tick, or Dermacentor albipictus. It has yet to be documented in Alaska, but it has wiped out much of the moose population in New England and started causing problems for moose populations as far north as Canada’s Yukon and Northwest Territories.

In recent years, nearly half of the mule deer examined in the Whitehorse area were found to be tick-infested, said Dr. Kimberlee Beckmen, the Alaska Department of Fish and Game’s wildlife biologist. That is ominous for Alaska, she said.

“All it takes is one mule deer with one female tick on it to come into Alaska, and that would completely devastate our moose population,” Beckmen said.

Mule deer have been well-established in the Yukon Territory since at least the 1980s, and in Alaska, people have been spotting them on sometimes fleeting occasions for a little over a decade.

Most sightings have been in the northern part of the Southeast panhandle, but some were as far north as Interior Alaska. Three mule deer were reported in 2013 near Delta Junction, one was photographed near the Fort Knox mine outside of Fairbanks in 2016 and one was struck by a vehicle and killed in North Pole in 2017, according to the Department of Fish and Game.

Though they are related to the Sitka black-tailed deer that live in territory stretching from the British Columbia rainforest to the Kodiak Archipelago, mule deer are different from their Alaska cousins.

The contrast is striking, said Nelson, the Skagway hunter.

“These deer are big, maybe twice the size of Sitka black-tailed deer,” he said. “Mule deer have enormous ears. They have ears like a mule.”

Adult Sitka black-tailed deer generally weigh 80 to 120 pounds, according to the Department of Fish and Game, while adult mule deer often weigh more than 200 pounds.

Nelson said he has seen mule deer occasionally in the Skagway area over the past few years. He had a light-hearted competition with a friend about who would be the first to hunt one. It was not until April when circumstances came together to result in a successful hunt – right in that friend’s yard.

“I just happened to kind of get lucky,” Nelson said.

The rules for hunting mule deer in Alaska, where the species is non-native and considered “deleterious,” are liberal. There are no seasonal restrictions and no bag limits. Even though it took until this year for Nelson to become the first hunter on record to harvest a mule deer in Alaska, state officials first authorized mule deer hunting in 2019.

The caveat for mule deer hunters is that the Department of Fish and Game wants them to submit tissue samples for testing. That is to screen for signs of tick infestations and for numerous problems like brain worm, also known as “moose sickness,” chronic wasting disease, different types of hemorrhagic diseases, bluetongue, worm infestation and other diseases or parasites.

Nelson provided abundant samples to the department: the hide, head and neck, liver, heart, lungs, spleen, lower colon and two lower legs with the hooves attached, according to officials with the Department of Fish and Game.

Importantly, Beckmen with the department said, there were no signs of hair loss or breakage in the hide, indicating that any tick infestation during the past winter was unlikely.

Nelson said he has been reading up on mule deer and the state’s concerns about ticks and other dangers. But he downplayed any contributions he might have made to state wildlife safety. “I wouldn’t say I’m super-noble or anything. I just wanted to get one,” he said.

Climate change, along with factors like road-building and agricultural development, have allowed mule deer to thrive in new territory even as some habitat is lost to development, according to the Department of Fish and Game.

Climate change is also helping spread the winter tick northward and westward.

The ticks do not travel on their own. Rather, they grow from eggs that are laid on the ground in the spring that grow into larvae that climb up plants in packs to latch onto passing hosts in the fall, a process known as “questing.” If they stay attached all winter, they develop into adults that repeat the cycle by dropping from their hosts in spring to lay eggs. Shorter winters and later snowfalls are increasing opportunities for successful questing by the ticks, scientists say.

In New England, moose have been found with tens of thousands of winter ticks embedded in their skin. The blood loss they cause can be fatal, especially to young moose. In Maine, for example, biologists in 2022 found that 86% of the moose calves they had collared died from tick infestations. In New Hampshire, the moose population now is only about half of what it was in the 1990s, according to state biologists there.

While mule deer can become infested with winter ticks, they also are able to get rid of them fairly effectively through self-grooming.

Moose lack those grooming skills. That results in moose rubbing and scratching off so much of their hair that they are called “ghost moose” because their bald spots make them look white.

Mule deer are not the only species expanding their range to Alaska.

Another such species is the mountain lion, also known as cougar. The Alaska Board of Game early this year approved a first hunting and trapping season for mountain lions. It is set to start on Aug. 1 in parts of Southeast Alaska.