|Scientists snare bear hair for DNA analysis|
By Julie Buckles
July 21, 2000
It's a culinary teaser meant for bears only: one-cup fetid fish oil and four liters spoiled cattle blood. Biologists slosh, slather and hang this and other concoctionscatnip, castor oil and molassesto lure bears under and over barbed wire fencing. "It's a putrid job," says Garth Mowat, a Canadian biologist and general manager at Wildlife Genetics International. But an effective one. The smells draw the bears to designated sights; the barbed wire snags their hair, and scientists collect and send it to the lab. In the root of each collected hair is enough DNA for geneticists to identify species, individuals and sex.
Using techniques from human forensic science, "bears are essentially tagged without ever being touched," Mowat says. Biologists are using this data to estimate population size, distribution and genetic variation, all indications of a population's health. Scientists analyze bear hair follicles using six markers to determine species, sex, and individuals. (Scientists compare regions of DNA to identify species: Black bears, for example, have 9 to 15 more units than grizzly bears.)
The larger challenge is getting the hair, which isn't as easy as it might sound. Grizzly bears weigh 300 to 800 pounds depending on their sex and the time of year. They are solitary, elusive creatures that, in the western United States and Canada, reside in dense forests. Biologists have sedated and collared them, drawn blood samples, flown overhead to count them and even positioned cameras with trip lines to capture them on film, without much success. "A lot of cameras were lost," laughs Curtis Strobeck, professor of biological sciences at the University of Alberta.
In 1995, undergraduate student Michael Proctor tromped through the mountains of British Columbia, Canada following black bears until he developed a procedure for collecting their hair. It turns out bears have no aversion to walking over, under and through barbed wire, as cattle ranchers will attest, when there's rotting blood on the other side. "And nothing separates the hair like barbed wire," he says.
Using Proctor's technique, bear biologists worldwide are snagging bear hair for its telling DNA: for sun bears in Malaysia, Asiatic black bears in Japan, panda bears in China, spectacled bears in South America, sloth bears in Asia, and brown bears in Europe. The United States adopted this method in at least eight states for black bears and in some western states for grizzly bears. Canadian researchers completed 17 studies in the last four years estimating grizzly bear populations in British Colombia and Alberta and have three more studies in the works.
This methodology could ultimately work for all fur-bearing animals, and is already being tested on lynx, bobcats, martens, and fishers, to name a few. Interested in DNA analysis for its wildlife management applications, researchers are learning how many bears there are, where they are, how they are related, paternity, maternity, and if there are ecologically significant populations that need stronger conservation efforts.
They have not mapped markers to a location on the bears' 74 chromosomes42 for giant pandas and 52 for spectacled bearsor even a particular chromosome. And there is little interest in undertaking a bear genome project. The reason, says Proctor, who is now working on his Ph.D. at the University of Calgary, is that the emphasis and funding in bear biology is ecological in nature. "The immediate threats to bears are human conflict, habitat fragmentation and cars on the highway, rather than disease or even genetic isolation," he says.
Proctor is studying the DNA of 900 grizzly bears in British Columbia. Using 16 markers for paternity, pedigree and inter-population analysis, he can look at individual bears, their parents and their offspring to get a picture of grizzly bear dispersal and movement. British Columbia has an estimated 10,000 to 13,000 grizzly bears that move along the mountain ranges. Highways running east to west cut through their habitat.
With data gleaned from these DNA samples, Proctor hopes to learn how much the highways impact grizzly bears: How do grizzly bears move between geographic areas? Do they cross highways? Mountain ranges? "We're using DNA to ask questions about the present and the future," he says.
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