On a frigid March day in 2011, workers with ENI Petroleum were busy moving construction equipment on and off Spy Island, a man-made offshore drill site in the Beaufort Sea a few miles off the coast near Ooliktok Point, when a female polar bear popped out of a deep snow drift under the artificial ground. She blinked wearily at her surprised neighbors, sniffed the air, then rolled around in the snow to clean off her white fur after a five-month slumber. In less than 12 hours, the island was shut down and evacuated.

Federal law requires that all industrial activity on Alaska's North Slope, the hub of the state's oil and gas activities, be conducted at least a mile away from the dens of pregnant polar bears. If a bear is disturbed, there's a high risk she'll abandon the site – and her newborn cubs. So, come December, just ahead of ice road construction, the state's wildlife biologists embark on a multiday bear-seeking expedition to map dens deep in the snowdrifts. It's a slow-going, high-stakes procedure, complicated by unreliable technology and harsh weather conditions. If a bear is missed, industry must either temporarily shut down operations or, in some cases, permanently reroute ice roads and close down drill sites – a multimillion-dollar expense. As a result, wildlife biologists are working hard to bolster detection technologies, with this winter marking their most intense field season yet.

To date, biologists have tested and relied upon Forward-Looking Infrared cameras mounted on helicopters and pairs of scent-trained dogs to stake out sleeping bears buried under several feet of snow. (Grizzlies can also be found up here, denning under dirt and roots.) But neither method is 100 percent accurate, says Craig Perham, who heads up the federal side of the bear den studies.

In 2009, Perham partnered with Dick Shideler of Alaska Fish and Game to bring in Shideler's two Karelian bear dogs, Kavik and Riley, so that they could study the efficacy of dogs in detecting polar bear dens. Karelians, a Russian and Finnish breed, have long been used to chase off problem bears in the Lower 48, and they're hardy enough for an Arctic climate, able to cover 5-10 miles each day. Moreover, they're pretty successful at finding dens – preliminary data analyses of the 2009-12 field study show the dogs were able to sniff out a polar bear roughly 75 percent of the time.

"But the detriment is that you have to have a dog that's trained to do it, and there aren't many," explains Perham, adding Kavik and Riley have since passed on. That's why biologists often rely on FLIR cameras operated by humans trained to detect polar bears' distinct heat signature in the snow. While FLIRs are dependable and widely available, their handlers are much more likely than dogs to pick up false positives (unoccupied dens) or false negatives (missing a den). Dogs, Perham adds, never get a false positive because the scent just isn't there.

But a sleeping polar bear only gives off a faint glow in the snow, 1-3 degrees warmer than her surroundings, which can be difficult to detect in certain weather conditions. "If you go out and look for dens when the sun is shining, because of what the sunlight is doing to the surface of the snow, it's nearly impossible to distinguish a bear den," says Todd Brinkman, a wildlife biologist at the University of Alaska Fairbanks.

This winter, Brinkman and researchers from the U.S. Fish and Wildlife Service and UAF used heaters to construct artificial polar bear dens on the North Slope to conduct test flyovers with drones in varying conditions to see how the heat signature changes. They hope they'll be able to pinpoint what weather is needed for the most accurate results. While sunlight can be problematic, so can wind, which creates too much noise for the infrared cameras. When the analyses wrap up next year, researchers will have established a set of industry guidelines for polar bear den detection. Perham thinks the ideal scenario is using FLIR under the right conditions and bringing in dogs whenever there's doubt.

"It's cool because it's one of those rare win-win situations," says Brinkman. "It's good for bears because you can avoid disturbing them; it's great for oil and gas so they can avoid the area; and it's a win for scientists who are trying to learn more about bears changing their behavior."

Thirty years ago, two-thirds of polar bears in the southern Beaufort Sea denned on sea ice, but now those bears have moved ashore. Right now, biologists are only detecting two to three dens per season, but as more and more bears move in, it's likely they'll be smack-dab in busy ice road intersections – making this work all the more important.

"We have this one industry that does a lot of work out in bear country, onshore and offshore," says Perham. "Nobody wants to push a bear out of their den if they can help it. We need to build a better mousetrap to be able to detect where these dens may be and protect bears."

Gloria Dickie is a freelance science and environmental journalist based in Boulder, Colorado. This article originally appeared on Arctic Deeply, and you can find the original here. For important news about Arctic geopolitics, economy, and ecology, you can sign up to the Arctic Deeply email list.

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