North Americas Mystery Cat
Analyzing DNA gleaned from hair samples, scientists are beginning to uncover secrets about the rare and elusive Canada lynx
- Gary Turbak
- Jun 01, 2003
DEEP IN WASHINGTON’S Okanogan National Forest, a lynx performs an ancient feline ritual: rubbing. Lured to this spot by wildlife biologists, the cat presses its cheek and neck against a nail-studded pad tacked to a tree. Moments later, the lynx resumes its predatory rounds, but leaves behind a few hairs—exactly the evidence the scientists need to document the species’ elusive presence.
Studying Canada lynx has always been a bit like counting smoke, as the shy cats dwell mostly in remote northern woods and only infrequently cross paths with people. "Amazingly, no one even knows where in this country lynx exist, let alone how many cats might be out there," says University of Montana wildlife biologist Scott Mills.
But today that is changing, thanks to Mills and other scientists engaged in an ambitious effort to document lynx everywhere the cats roam. Employing a mix of low-tech, high-tech tools as disparate as aluminum pie plates and mitochondrial DNA, the survey already has revealed at least one previously unknown hotbed of lynx activity. "Our goal is to appraise the distribution of lynx across its entire U.S. range," says coprincipal investigator Mills.
The majority of the continent’s lynx reside in the boreal forests and taiga of Canada and Alaska. Yet outside Montana, Washington and Maine, long known to harbor resident lynx, the species’ status overall in the lower 48 states has remained largely a mystery. Although two dozen states have historical records of the cats, most biologists suspect lynx were never abundant in this country.
Photo: © MILO BURCHAM
CURIOSITY AND THE CAT: Cute as domestic tabbies, lynx kittens in Montana’s Mission Mountains already exhibit curiosity, a classic feline trait used by researchers to attract the cats’ elders to rubbing stations in the forest. Once lured to a station, a cooperative lynx deposits a few of its hairs for DNA testing.
In the late 1990s, growing concern over the cat’s scarcity spawned a push to list lynx federally as a threatened species (which occurred in 2000). One obvious requirement for conserving the cat was a thorough assessment of its U.S. range. Accepting the challenge, researchers at the U.S. Forest Service’s Rocky Mountain Research Station and the University of Montana (both in Missoula) teamed up to launch the National Lynx Survey in 1998. The task appeared daunting, explains Mills, because "no one had ever before attempted to survey a wide-ranging, mobile carnivore across so much territory." To do it, the scientists turned to a classic feline quality: curiosity.
A few years earlier, John Weaver, a Montana field biologist with the Wildlife Conservation Society, had discovered that lynx, like most cats, can be enticed to rub against objects placed at predetermined locations—when lured to the spot by a combination of visual and olfactory attractants—leaving a few hairs behind. Analyzed for DNA, that hair can document the presence of lynx.
To build on Weaver’s work, Rocky Mountain Research Station scientists Kevin McKelvey and Greg McDaniel went to the Canadian Yukon’s lynx-dense Kluane National Park to test hair-collection techniques. One crucial question was which olfactory attractant would best draw lynx to the rubbing stations. Although four commercial lures showed promise, a homemade concoction of beaver castoreum and catnip oil held even greater lynx appeal. "We’re not sure why our mixture worked better," says survey coprincipal investigator McKelvey, "but we did use a lot of catnip oil." The homespun recipe also attracted the fewest non-target species.
The rubbing stations are decidedly low-tech affairs. First, the beaver-catnip oil is worked into a four-inch square piece of carpet that has been studded with small nails. The smelly pad is then attached, nails protruding, at lynx-head height to a tree. Finally, a nine-inch aluminum pie plate is dangled on a wire from a nearby branch. The plate’s purpose is to draw the initial attention of curious and sharp-sighted—but not keen-nosed—lynx. Investigating closer, the cat whiffs the concoction and instinctively rubs the pad, leaving a few hairs on its nails. In charge of the laboratory portion of the project, Mills meanwhile was perfecting protocols that would allow the lab to reliably and consistently distinguish lynx DNA from that of other animals.
The survey was officially launched in 1999, when hundreds of biologists and wildlife technicians began to set out thousands of rubbing stations across potential lynx habitat in 12 states, primarily those bordering Canada and in the mountainous West. Typically, five stations are evenly spaced along a 400-yard transect. Twenty-five transects at 2-mile intervals complete a grid of 125 stations in each survey area. Later, researchers return to the sites to collect whatever hair has been deposited, then send the samples to Mills’ laboratory in Missoula.
In the lab, Mills and his colleagues painstakingly extract DNA from the hair. With arcane tools such as polymerase chain reactions (amplifying very small amounts of DNA into useable quantities), the science boils down to comparisons: In previous work, Mills and others identified genetic markers unique to certain wildlife species—DNA that always shows up, for example, in a fox or cougar or lynx.
What creatures left hair on the scientists’ rubbing pads? Lots of them, it turns out. So far, 17,000 pads set out over the course of three field seasons have collected 2,505 useable hair samples—mostly from animals other than lynx. About 45 percent of the hits have come from black bears. Other rubbers include bobcats, cougars, dogs and wolves (whose DNA is indistinguishable from one another), deer and even cows. Lynx have contributed just 74 hair samples (not necessarily from 74 different animals), which is not surprising, says Mills. "There probably are not a lot of lynx out there."
Most lynx hits came, as expected, from known populations in Montana and Washington. In Maine, where lynx were also expected to volunteer some hair, snagging stations did not go out until 2001, yet they still recorded two lynx hits.
There also were a few surprises. Early in the study, lynx hair showed up in two places no one thought the cats existed: Shoshone National Forest in Wyoming and Boise National Forest in Idaho. Initial excitement faded, however, when neither follow-up snow tracking nor additional hair collection could find further evidence of lynx in either place. "Those cats were probably just wanderers," says McKelvey. During the most recent field season (2001), lynx hair also turned up on pads in Yellowstone National Park and Utah’s Wasatch Mountains. Researchers are still hoping to confirm lynx presence in those two regions.
Early last year, Minnesota took center stage on the lynx discovery front, as anecdotal reports of lynx sightings increased. Because the state’s large population of black bears can overwhelm snagging stations, researchers decided to try collecting hair in winter when the bruins are hibernating. Following suspected lynx tracks in the snow, the researchers collected hair from day beds and scat (rubbing stations are too difficult to access in winter). DNA collected this way has already yielded 20 lynx hits from at least 6 different cats, suggesting a possible new hotbed of lynx activity. "We’ve verified the first lynx presence in Minnesota since 1993," says McKelvey. "Lynx are definitely back in that state."
Though the survey is for the most part complete, participants will continue to collect samples in Minnesota and a few other regions where more information is still needed. "We now have a good idea of the current lynx range in the United States," says McKelvey, who hopes to have a preliminary report ready for review this summer. In addition to locating lynx in many areas, the survey failed to find the cats in others. McKelvey suspects the cat’s range "is more restricted than we might have thought."
Photo: © HOWIE GARBER
OUT OF THE SHADOWS: Nearly complete, the National Lynx Survey has confirmed the presence of lynx in U.S. states previously not known to harbor them. The number of cats in the lower 48 states will almost certainly turn out to be fewer than the Canadian population, which includes this lynx (above) in the Yukon’s remote Kluane National Park. Interbreeding between Canadian and U.S. lynx—also confirmed by DNA analysis—may be keeping the smaller southern populations genetically healthy.
Yet absence of hair at a rubbing station does not necessarily mean there are no lynx in the area. Using tracks and video cameras, scientists have discovered that lynx may approach a station but choose not to rub. And at the northern tip of Maine, state wildlife biologists located one new lynx population based primarily on winter snow tracking, says Peggy Struhsacker of NWF’s Northeastern Natural Resource Center, which is assisting the state effort.
Beyond yielding lynx location data, however, the survey represents "an important part of an ongoing revolution in how we determine the status and distribution of rare and secretive species," says Keith Aubry, principal research biologist at the forest service’s Pacific Northwest Research Station in Olympia, Washington. "It’s tremendously important to base conservation decisions on physical, verifiable information," he adds. "The National Lynx Survey is providing that kind of data for lynx, and it’s doing so essentially everywhere lynx likely occur and at relatively low cost."
At this time, survey researchers are aiming only to tally the number of lynx hits, not to identify individual animals or make other genetic comparisons (a much more difficult process with the few hairs typically left by lynx). But such work is on the horizon, says Mills. "We hope someday to use DNA to calculate lynx abundance, identify many individuals and track movements among populations."
Perhaps the most important mystery DNA analysis could solve would be the extent to which lower 48 populations are genetically influenced by cats migrating south from Canada. Biologists know that Canadian lynx numbers follow boom and bust cycles that can cause some cats to travel great distances—up to 600 miles in certain cases. Some of these travelers are known to breed with local cats, and one theory holds that emigrating Canadian lynx play a crucial role in keeping isolated U.S. populations genetically healthy by preventing inbreeding.
Last summer, Michael Schwartz, a biologist with the Rocky Mountain Research Station, published a study in Nature summarizing comparisons of DNA (from tissue samples, not hair) of nearly 600 lynx in 17 Canadian and U.S. locations, some nearly 2,000 miles apart. "The genetic profile of lynx in Canada and those in the U.S. is really quite similar," Schwartz discovered, "so there is apparently a lot of gene transfer taking place." Schwartz believes that "migration of Canada lynx southward is probably very important to the continued existence of some U.S. populations."
Yet the extent and importance of this genetic transfer remains unknown. With DNA analysis poised to answer this and other critical questions in wildlife research, there’s a good chance that a few strands of hair may one day help remove imperiled species from the threatened or endangered list. When that happens, some pundit is sure to say—correctly—that these creatures were saved by a hair.
Although Montana journalist Gary Turbak lives in lynx country, he is still waiting to see his first lynx in the wild.
NWF Priority
Keep The Wild Alive
The Canada lynx is one of 25 species targeted by NWF’s Keep the Wild Alive™ campaign, which promotes the conservation of threatened and endangered species—from large charismatic creatures such as the Florida panther, whooping crane and humpback whale to obscure reptiles, plants and insects, including the arroyo southwestern toad, Mauna Kea silversword and Karner blue butterfly. Launched in 1998, on the 25th anniversary of the Endangered Species Act, the campaign harnesses a combination of education, outreach, advocacy and conservation initiatives. Another component, the Species Recovery Fund, awards small grants to local organizations that conduct on-the-ground projects to protect imperiled species.
To learn more about lynx, see http://www.enature.com/home/.
Rubbing Up Against DNA
DNA information gleaned from wildlife hair has proved invaluable to other scientists studying elusive creatures such as carnivores. Today it is possible to identity DNA from scores of wildlife species, including fishers, martens, skunks, bears and wolverines. At Voyageurs National Park in Minnesota, for example, biologists wishing to know more about their resident weasels have set out lengths of 1.5-inch diameter plastic pipe with chicken wings tucked inside. To access the treat, a weasel must crawl through rough hardware cloth covering the pipe’s open end, which pulls off a few of the animal’s hairs. "Hair snagging is the way of the future," says Voyageurs wildlife biologist and National Lynx Survey participant Jim Schaberl. "It’s nonintrusive, meaning we no longer have to wrestle the animal down and put a radio collar on it."
One of the most comprehensive hair snagging projects to date targeted grizzly bears in and around Montana’s Glacier National Park, where U.S. Geological Survey research ecologist Kate Kendall set out more than 1,250 bear hair snagging stations between 1998 and 2000. Each station consisted of a "corral" created by stringing a single 80-foot strand of barbed wired around a small cluster of trees. In the center of the enclosure researchers deposited a putrid, pungent mix of blood and rotting fish.
Led by their keen noses, bears would visit the bait, and—if all went well—deposit some hair as they crossed over or under the wire. With bears lured much more easily than lynx, Kendall got hair (from either grizzly or black bears) from 80 percent of her collection sites. In addition, the researchers placed hundreds more (unbaited) barbed-wire snags on traditional grizzly rubbing trees.
"Stringing barbed wire and mixing stinky bait is pretty low-tech," admits Kendall, "but this is a great new tool that lets us collect data we couldn’t get before." For many years, for example, the only available population estimate for Glacier’s grizzlies—derived from old and possibly unreliable data—put the tally at about 200 bears. Kendall’s hair analyses, however, identified 187 and 197 individual grizzlies during 1998 and 2000 respectively, and since many bears probably never leave hair at a station, she estimates that the total population is somewhere between 273 and 381 animals. Her work also revealed that about 50 to 55 percent of the grizzlies are female, a number never before available and one that is crucial to conserving this slowly reproducing, threatened species.
