by Gail Jokerst
Ever since visitors first began touring Glacier National Park, they've asked, How many bears live here? It took almost a century to find the answer. But thanks to genetic fingerprinting, biologists now have a good idea how many grizzlies roam Glacier Park.
The key to counting grizzlies is something called DNA. That stands for deoxyribonucleic acid. All living things-from hummingbirds to horses to humans-have a genetic code. This code is found in the DNA that is part of all cells. Skin and bone cells contain DNA. So do hair cells, which provide a great source of DNA when the root still clings to the hair.
By studying genetic codes, biologists can learn which animal the DNA came from. They can tell moose DNA from mouse DNA and figure out if two moose or two mice are related.
Think of DNA as fingerprints. No one elses fingerprints match yours. Just as we each have one-of-a-kind thumbprints, every bear has its own genetic code. Biologists read this code to see if it comes from a grizzly or a black bear. Then they identify individual bears and bear families from the codes.
Scientists realized they could count Glaciers grizzlies if they could genetically fingerprint them. But first, they needed a safe way to collect bear hairs with plump roots.
Knowing that bears scratch their backs on certain trees and that they never pass up a free meal, researchers used that information to obtain hairs. First, field crews trekked hiking and game trails (which grizzlies also use) to find trees that bears like to rub against.
How did they spot back-scratching trees? By looking for claw marks on trunks and hairs wedged in the bark. Once they found those trees, workers tacked strands of barbed wire on the trunks. Every 14 days, a crew returned to pluck the hairs with tweezers and tuck them into envelopes.
In areas far from trails and people, crews also set harmless scent stations to attract, not catch, bears. Each station was simple: an old log or tree stump in the middle of an open area, circled by 80 feet of barbed wire. To lure bears closer, crews doused the wood with a brew made from rotten fish and cow blood.
The lure smelled yucky to people, but bears craved it. When they caught a whiff, theyd beeline to the bait, stepping over the wire and snagging some fur on the way. Bears were rewarded with a nose-tickling aroma but no free lunch.
Workers returned two weeks later, after the odor evaporated. Sometimes, the stations looked just like when they were set. If not for hairs snagged on the wire, no one would have guessed bears had checked out the bait. Other times, the stations looked as messy as a birthday party after the kids had gone home. Hidden cameras discovered why. Some bears loved the smell so much they rolled on the logs or rubbed their faces in the lure. Whether the scent stations were trashed or tidy didnt matter. Crews gathered the hairs, coiled the barbed wire, and moved the station to another location.
A genetics laboratory analyzed the collected hairs and identified 197 grizzlies in Glacier. In addition, scientists figure 84 more grizzlies that didnt snag fur on bark or barbed wire live here.
This was one of the first studies to use DNA for counting animals in a large wilderness area. It proved so successful that wildlife managers who monitor grizzlies on nearby state and federal lands have begun a similar but bigger survey.
This new study, the Northern Divide Grizzly Bear Project, covers bear habitat in northwestern Montana. Like the earlier study, its goal is to count grizzlies. After that information becomes available, wildlife managers will know how many of these threatened animals crisscross the region. Future surveys will help determine if bear numbers are increasing or decreasing.
Part of the expanded project occurs in cattle country, which can be a problem. Scientists learned from the Glacier study that cattle like the nasty-smelling lure as much as bears do! Cows wrecked every scent station they visited. So fences had to be built to let bears in and keep cows out.
Next year, field workers will put up scent stations and tack barbed wire to rub trees in an area as big as Maryland and Delaware combined. Crews will return five times next summer to pluck bear hair and move the stations to new sites. They will also string not just one but two strands of barbed wire around the bait. The strand lowest to the ground will catch hair from cubs and yearlings.
When the DNA results come back in 2006, we will have the best estimate ever of how many grizzlies really live in northwestern Montana.
Visit the USGS Northern Divide Grizzly Bear Project to read more about bear DNA studies on the web.
This recipe makes a red brew that lures bears to scent stations. It may look like tomato soup, but smells nothing like it, you can be sure!
Fill a 55-gallon drum with fish. Punch holes in the drum to prevent explosion. Let age 2-3 months. Collect juice. Toss skin and bones. Fill another 55-gallon drum with cow blood. Addanti-coagulant (a chemical that prevents blood clots). Let ripen 2-5 weeks.
Combine and place in odor-proof containers:
4 cups stinky fish juice