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This GPS system is a real bear.

Eight Montana grizzly bears have been outfitted with GPS trackers in an ongoing study that could bring some unnerving news to hunters.

The study is aimed at bolstering the theory that grizzlies, which can be as stealthy as they are ferocious, stalk hunters from as close as the length of a football field in order to steal their prey. Already, data has shown at least one grizzly following oblivious elk hunters almost from the moment they left the parking lot, according to the Billings Gazette. Scientists believe the bear may have been following the humans in hopes of getting to a fallen elk before they did.

"Bears opportunistically scavenge carcasses throughout the active season and commonly usurp kills of other predators, such as cougars and, since their reintroduction in 1995, gray wolves,” stated a report last year by the Interagency Grizzly Bear Study Team. “Remains left by hunters also provide grizzly bears with meat, and bears are attracted to areas outside of national parks when these remains become available during the fall.”

The Interagency Grizzly Bear Study Team, part of the U.S. Geological Survey, started the project over the summer, by tagging the grizzlies in the Grand Teton National Park. Next, the study team asked elk hunters to voluntarily carry some 100 GPS units that track their routes.

In the most clearly detailed example, a group of hunters turned on their GPS devices moments after leaving a parking area at around 6 a.m. When scientists analyzed their movements later and contrasted them with those of a nearby grizzly, it became clear the bear was tailing them.

The bruin stayed downwind of the hunters, at one point coming within 100 yards of them as they moved around a lake. At around noon, the bear bedded down for a nap, but easily picked up the hunters’ trail again when it awoke, according to the report. Grizzly bears’ have a sense of smell seven times greater than that of a bloodhound, and 100 times that of a human by some estimates. Grizzlies also possess a Jacobson’s organ in the roof of their mouth that can detect heavier moisture-borne odors.

Scientists tracked the bear as it appeared to smell an elk carcass from 4 miles away, follow the scent and even wound up swimming across the lake to get to it, according to the report. They also observed that the bear made some evasive maneuvers, possibly to avoid an untagged grizzly competing for the same meat.

“The temporary movements away from the carcass could be indicative of this particular bear being ‘pushed off’ the carcass by a more dominant bear,” said Frank van Manen, of the Interagency Grizzly Bear Study Team based in Bozeman.

Grizzlies have been known to steal the prey of hunters and fishermen alike. Animals such as elk may travel for miles after being wounded, leaving hunters the task of tracking them even as bears may be doing the same.

So attuned to the movements of hunters are the bears that scientists believe they may even listen for the sound of gunshots, knowing that they signal a meal to be scavenged. Grizzlies are known scavengers, and officials noted there have been cases of the mighty bruins attacking hunters as they dressed elk in the field. Montana Fish, Wildlife and Parks now requires successful bison hunters outside of Yellowstone National Park to move carcasses and gut piles 200 yards away from homes, roads and trails to lessen the chances of human-bear interactions, according to the Gazette.