Alaska News

Genetic differences emerging among moose divided by Glenn Highway

Behavior that makes some Anchorage moose safer might be having an unfortunate side effect -- less variety in their sex lives, potentially.

A newly published study shows that moose separated by the Glenn Highway -- a busy, partially fenced traffic corridor leading north out of Alaska's largest city -- are starting to show subtle differences in their genes.

The study, using data gathered from 2009 to 2012, evaluated movements of radio-collared female moose in the habitat that is bisected by the highway. It also used genetic data gleaned from ear plugs and blood from the collared moose and tissue samples from 15 moose killed by hunters in the area.

The result? The moose are divided into two genetic clusters on either side of the highway, with differences that are small but detectable.

"We might be picking up the very beginnings of a split," said Robert Wilson, the lead author of the study, which was published Feb. 5 in the journal Conservation Genetics.

No such genetic division was found in a group of Kenai Peninsula moose used for comparison, the study said.

In a two-year period, only 68 Glenn Highway crossings were made among all the 25 Anchorage-area collared moose, according to the study. Only 14 of the animals crossed at all, and most of the crossings were made by only two individuals, according to the study. Moose along the Glenn Highway moved over a much smaller area than did their counterparts on the Kenai Peninsula; on average, each of the Anchorage moose in the study had a home range of 21.2 square miles, compared to 40.9 square miles for the Kenai Peninsula moose in the study.

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When it comes to the Glenn Highway, there are good reasons why the moose do not cross the road.

Since the late 1980s, the highway has become increasingly impenetrable for the animals. In 1987, a fence structure spanning about seven miles was erected specifically to keep the moose out of traffic and out of trouble. Traffic volume on the Glenn has risen by roughly two-thirds since then, with an average of 54,201 vehicles moving along the route each day in 2012, according to the study.

"When an animal walks up and just sees this massive wall of vehicles, it's not likely to cross," said David Battle, an Alaska Department of Fish and Game biologist who contributed to the study.

The research does not provide any conclusive evidence about reduced cross-highway mating, or even any reproduction information whatsoever. It does not follow movements of any male moose, much less any encounters between bulls and cows, on either side of the Glenn, during the fall mating season.

The highway is not the only thing that could be behind the genetic results, notes study co-author Sandra Talbot, a wildlife geneticist for the U.S. Geological Survey.

"It's entirely possible that something else is causing the pattern," Talbot said. "It may be that these guys just like to hang out in their own patch."

Still, the emerging genetic differences on either side of the Glenn Highway line up with a pattern seen elsewhere -- specifically, in wildlife populations with habitats crossed by barriers that restrict movement.

A study of bighorn sheep in California, published in 2005, found that the animals living amid highways and other manmade barriers lost up to 15 percent of their genetic diversity in 40 years. Also in California, pumas are losing genetic diversity as their habitat becomes fragmented by highways, according to a study published last October. Roads in Germany and Switzerland have likewise been blamed for "genetic subdivision" among voles in those countries.

Concerns have arisen that the partial U.S.-Mexico border barrier will cut off migration, and thus genetic diversity, for numerous species, including bobcats and coyotes and endangered amphibians and reptiles. Along the Israel-Palestine border, concerns about wildlife segmentation are so great that the Israel Defense Forces have permitted some openings in the imposing West Bank barrier to allow small animals to pass through.

The Glenn Highway fencing incorporates its own features designed to allow limited animal movements. But they are unsatisfactory, biologists say.

The one-way gates that are spaced along the fence sometimes freeze in place in winter, Battle said. And sometimes calves can squeeze through the gates but not their mothers, causing consternation for the animals and dangers for any people who might be in the vicinity, he said.

More problematic is an underpass constructed at Ship Creek that was envisioned as a convenient passageway for animals but is "now understood to be woefully inadequate for wildlife," study co-author Sean Farley, an Alaska Department of Fish and Game research biologist, said in an email. The underpass is too small, and becomes even smaller and less enticing to long-legged moose when it fills with water that freezes in cold weather, Farley said.

Alternate technology is available that could help moose safely cross busy roads, Battle said.

"Ideally, we would see a vegetative overpass," he said, such as those used in Canada's Banff National Park. "They have been found to be very effective in allowing animals to move." But they are expensive, and "so far that has not been something that anybody is willing to do."

Although the study found a subtle difference in genetic structure, it did not find signs that there has been a loss of genetic diversity -- yet -- among moose of the upper Ship Creek/Joint Base Elmendorf-Richardson area, a population estimated at 347 in 2013.

But the situation is worth monitoring in the future, the study authors said. Similar genetic studies could be conducted for other animals living on both sides of the Glenn Highway, from tiny wood frogs to porcupines to, possibly, bears, said Talbot.

Yereth Rosen

Yereth Rosen was a reporter for Alaska Dispatch News.

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