It may not be the stuff of a television series – think CSI: Black Bear – but the science of DNA may help state wildlife biologists figure out how many black bears are in the forest.
“Any animal you can’t see is hard to keep track of,” says Tom Stivers, Fish, Wildlife and Parks wildlife biologist in Lewistown.
Part of the problem is the nature of black bears: They are unpredictable, solitary, forest animals. They don’t herd in the open like deer or antelope. That means you can’t count them from an airplane, or by looking at a hillside on a wildlife management area.
To remedy that, FWP wildlife biologists are counting bears by collecting hair and analyzing the animals’ DNA, which is unique to each animal like a human’s fingerprint.
Bear hair was gathered at scent stations in the Snowy and Judith mountains near Lewistown in June 2002. The study area was in bear management unit 411, which covers the Snowy Mountains in FWP Regions 4 and 5.
Wildlife biologists set up 206 scent stations, randomly distributed across the 1,028-square-mile study area. Each scent station was about 15 feet square and surrounded by a single strand of barbed wire.
When a bear crawled under or stepped over the wire to investigate the smelly lure, it left a strand of hair, which was studied to identify that bear’s DNA. Because each animal has unique DNA, that bear was considered marked.
Next, hair is taken from bear hides presented by hunters as required by law. Again the DNA is studied and the bear identified, or “recaptured” in the parlance of wildlife biology. By comparing the number of bears marked with those recaptured, biologists can estimate what portion of the population hunters are taking.
Around Lewistown the answer is about 6 percent of the males and 5.4 percent of the female bears.
“That’s well within what’s considered acceptable,” Stivers says. “Anything less than 15 to 20 percent is OK.”
Last year, a federal study collected hair at scent stations on the Rocky Mountain Front to look at grizzly populations. The laboratory analysis will take place this year.
Because black bears left hair at the scent stations, too, state biologists will use that DNA data and compare it to bear harvests. Biologists last fall snipped hair from black bear hides taken by hunters along the Front. The effort will continue this spring.
DNA studies can also produce population estimates. In the Snowy Mountains, the DNA effort generated an estimate of 265 bears and helped biologists monitor the female bears killed each year.
“The female harvest rate is the most important,” Stivers says. “Over the years, the number of females harvested in BMU 411 has been between 30 and 40 percent of the total harvest, which is around 20 to 30 bears a year. When compared to the population estimate of 265 bears, that suggests that the female harvest ranges between 5 and 10 percent each year.”
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