BOZEMAN — From almost four miles away, the grizzly bear appeared to have picked up the elk carcass' stench.
Researchers were able to revisit the grizzly's trek as it walked along the edge of a lake, eventually swimming across the end of the water to reach the carcass, because the bear was wearing a GPS collar. The same location information showed the bear visiting and moving away from the carcass several times in following days.
"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.
Even the threat of a confrontation with a larger bear wasn't enough to shoo the grizzly bear completely away from the prime source of protein.
"These carcasses have a lot of pulling power and holding power," said Mike Ebinger, who is leading a study for the IGBST.
Ebinger's study, being conducted over two years in Grand Teton National Park, is meant to analyze grizzly bear-hunter interactions. The scientists have several objectives.
They want to know if the density of grizzly bears changes over time relative to the hunting season — in other words, are rifle shots like ringing a dinner bell that congregates bruins? To find out, hair snares have been set up to collect bear DNA. Cameras at the snare sites allow the scientists to match the hair with specific bears that were photographed.
They also will plot where the elk are being killed by hunters in space and time.
"We want to know on a daily basis where the gut piles are," Ebinger said. "We're not interested in the elk gut piles, but in how the grizzly bears respond to them. They can be a very attractive resource."
Perhaps most unusual, Ebinger will find out how hunters and grizzly bears interact — how they influence each other — by comparing the data from GPS-collared bears to GPS units loaned to hunters to track their whereabouts.
To begin the study, this summer the study team attached GPS collars to eight bears.
To track elk hunters, the study team has asked them to voluntarily carry and return 100 GPS units that can track their routes. After a day's use, the units can be dropped off, their information downloaded, and the GPSes are recharged and sent out again. To encourage cooperation, participants will be entered in a raffle.
"We've had a really great response," Ebinger said.
In one encounter already tracked, Ebinger showed slides demonstrating how the data could be combined. As one group of hunters left a parking area at around 6 a.m. they turned on their GPS. As they moved around a lake in search of elk, a nearby GPS-collared grizzly starts moving in the same direction behind and to the side of the hunters — probably downwind of them. At one point, the bear is within about 100 yards of the hunters who never knew it was there.
After bedding down around noon, the bear picks up the hunters' now-cold trail and follows them again, possibly hoping they would shoot an elk. Even though the human route was now hours old, a bear would have no problem following the hunters. Some estimates put a grizzly's sense of smell as seven times better than a bloodhound's, and studies have calculated the size of the bruin's scent-detecting area as 100 times larger than a human's. Grizzlies also possess a Jacobson's organ in the roof of their mouth that can detect heavier moisture-borne odors.
The interest in grizzly-hunter interactions has a long history, Ebinger said. Several incidents of bears attacking hunters have been recorded over the years, and one hunter in northwestern Montana was killed by a grizzly in 2001 as he dressed out an elk he had shot. 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.
Hunters and bears often collide in the fall because of a shared interest in eating fresh, wild protein. Fall hunting season floods the timber with bow- or rifle-toting men and women who are trying to move quietly and stealthily to sneak up on elk and deer. Bowhunters even wear cover scents, such as elk urine, and bugle or cow call to sound like an elk.
At the same time, grizzly bears are in what's known as hyperphagia, a stage before they enter hibernation when they are consuming as many calories as possible to gain fat for their long winter nap. With gut piles and carcasses left by hunters an easy source of food, it's only natural that the two predators — human and animal — will sometimes run into each other.
"As Mike indicated in his presentation, these movements show that ungulate carcasses tend to keep bears close to the area," van Manen said. "With GPS data from other bears we can start investigating these type of interactions."
Ebinger stressed that the work isn't mean to revise hunting regulations in places like Grand Teton National Park. Yet the work should be translatable to other areas where hunters and grizzlies are likely to interact.