The Benefits of Badgers

These burrowing prairie weasels

12-01-1995 // Les Line

A celebrated folklorist of the American Southwest, J. Frank Dobie until his death in 1964 collected fine stories the way some people collect fine wines, and like oenophiles he took great pleasure in sharing his treasures. In one famous tale, Dobie told of an acquaintance who "has twice seen dust rising from a prairie dog town some distance away and then, through binoculars, watched a badger digging while two waiting coyotes flanked him. In each instance the badger got meat, but a prairie dog or two came out by him into the mouths of the coyotes."

Like most Texans, the author was guilty of a stretch now and then, so experts tended to dismiss his animal yarns as more fiction than fact. For centuries, however, the Navajo people had passed along stories about coyotes and badgers hunting together, and Dobie surmised that nature was hiding something important about the brush wolf's camaraderie with this cousin of skunks and weasels. He was right.

The big secret was revealed not long ago by a rare breed of scientist: a badger biologist. It's true that coyotes often run around with badgers, Steven Minta of the University of California in Santa Cruz reported in the Journal of Mammalogy in 1992. On Wyoming's National Elk Refuge, where Minta did his research, far more coyotes hunt with badgers than hunt alone. Instead of wasting time and energy stalking ground sagebrush, the coyotes simply wait for badgers to flush the rodents from their burrows. Moreover, Minta observed, badger-befriended coyotes catch a third more squirrels than do solitary coyotes.

The alliance benefits the badgers, too. Minta theorizes that ground squirrels hunker down in their holes when coyotes are standing guard. allowing the badgers to spend more time underground catching and eating prey. There's more: With their acute eyesight and hearing, coyotes can locate squirrels at a distance, allowing them to function as spotters for the ground-hugging badgers. The coyotes encourage the badgers to move to more productive digging sites by various kinds of play—mock pursuit, bowing, dancing and face-pawing. Sometimes a badger and coyote will simultaneously charge an area with a dense squirrel population, panicking the rodents and catching them above ground or trapping them in shallow and unconnected tunnels. Coyotes sometimes kill young badgers, Minta noted, but the absence of any mutual predation among adults, and their complementary hunting techniques, led to this "limited, two-species social system."

The Invisible Carnivore

There is good reason why science waited so many years to corroborate and explain an association that Native Americans, western settlers and early naturalists took for granted. Badgers are solitary, usually forage at nightand snooze away daylight hours in dens. In other words, badgers are invisible most of the time, making them unpopular research subjects. But these days, determined scientists are unearthing many new details about the ecology of this four-legged backhoe and are even using it in a critical study of the hazards posed by a toxic Superfund site in Colorado.

Biologist Barbara Ver Steeg of the Illinois Natural History Survey has just completed a six-year study of badgers on Midwest farmlands for the state's department of conservation. Her work is pioneering; until now, most badger research has taken place in the West. One significant finding: Illinois badgers are land barons compared to their counterparts on the plains. Badgers on the plains, which have access to populous colonies of ground squirrels and prairie dogs, have small home ranges covering 1 to 3 square miles. In Illinois, where patches of undisturbed cover are scattered between corn and soybean fields, badgers have to roam far and wide to find enough food, so individual ranges are enormous, spanning 8 to 14 square miles.

The badger is a native of North American grasslands and deserts, and if you draw a line from Houston to Kansas City to Columbus to northern Michigan, you've roughly defined the eastern extent of its range. John Madson, a prairie poet who grew up in Iowa badger country, described the beast as being "put together funny—a bowlegged, pigeon-toed doormat that sweeps the ground with its trailing end." Funny-looking it may be, but the badger is put together perfectly for a job it does better than anything else: digging.

For starters, the badger's head is wedge-shaped for nosing into the holes of burrowing rodents ranging in size from deer mice to woodchucks, and a keen sense of smell tells it whether anyone is home. Thanks to thick fur and loose skin, a badger can turn around with amazing ease in a tight burrow. And a nictitating membrane protects its beady eyes from flying dirt.

Oh does the dirt fly! Front claws up to 2 inches long loosen the soil, while short, shovel-like hind claws push it out of the burrow. "At high speeds," says Ver Steeg, "a tunneling badger throws a plume of dirt into the air behind it." A human wielding a shovel, she notes, is no match for this powerfully built, 15-pound carnivore.

Superfund Badgers

In addition to serving as a subject of natural-history studies, the badger is a key player in biomonitoring research that will help authorities assess risks to wildlife and human health on a national wildlife refuge that is also a Superfund toxic-waste site. On the shortgrass prairie of Rocky Mountain Arsenal in Colorado, environmental toxicologist Dale Hoff is investigating how the badger population is affected by pesticide wastes that were dumped on the scene during decades of use by the military and by a pesticide company.

Dieldrin, a compound that farmers apply directly to soil to kill grasshoppers and beetle larvae, is the foremost chemical of concern. "Dieldrin is readily absorbed through the skinby both badgers and the prairie dogs they dig out on the arsenal," says Hoff, a Clemson University graduate student. "If badgers are foraging in contaminated areas, they're getting a double whammy from the soil as well as the food chain, and bioconcentration of the chemical in their fat could become pronounced."

The U.S. Army used the 27-square-mile arsenal, about 10 miles from downtown Denver, to manufacture chemical weapons from the early days of World War II until the 1960s. The Army also leased facilities to Shell Chemical Company for the production of agricultural pesticides. Because of weak regulations and the lax attitude of the time toward chemical-waste storage and disposal, the arsenal's soil, ponds and groundwater ended up contaminated with such now-banned poisons as dieldrin, aldrin, endrin and DDT as well as mercury, arsenic, chromium, benzine and other dangerous compounds. In 1987, the U.S. Environmental Protection Agency (EPA) placed the arsenal on the Superfund National Priorities List for pollution cleanup.

But Rocky Mountain Arsenal, though sandwiched between a sprawling city and its new international airport, is also an island of wildlife habitat that includes a communal roost for wintering bald eagles. In 1992, Congress passed an act giving the U.S. Fish and Wildlife Service (FWS) responsibility for managing the land as one of the country's few urban national wildlife areas. However, the former military post will not become a permanent part of the National Wildlife Refuge System until cleanup is completed.

Last June, after a decade-long stalemate over what cleanup methods would be used, the Army, Shell, EPA, FWS and the State of Colorado unveiled a $2-billion "remedy." The plan includes excavation of contaminated soil, some of it to be buried in a state-of-the-art landfill, plus entombment of the worst waste-disposal sites under 6 inches of concrete and 4 feet of dirt. Congress, however, must appropriate funds for the task, and that is not a given in the present anti-environment climate on Capitol Hill.

Meanwhile, public use of the arsenal is strictly controlled because of safety concerns. Still, 40,000 children and adults came to the refuge last year k)r school outreach programs, guided tours on double-decker buses and special events like Bald Eagle Day. And FWS, anticipating that annual visitation will reach 150,000 in a few years, plans to build a new visitor center with two tram routes that will carry people to trails and educational sites.

Sentinel Species

Scientists at the refuge call the badger a sentinel species, one that provides clues about the health of its ecosystem. The category also includes animals at other points in the food chain. "We look at deer mice, pocket gophers, starlings, magpies, kestrels and great-horned owls" says Rick Roy, one of the biologists involved in the biomonitoring studies.

Roy notes that songbirds on the refuge die from eating dieldrin-laced grasshoppers, beetles and worms, while raptors accumulate lethal levels of the chemical from the small mammals and birds in their diet. "We've found the trouble areas," says Roy. "It's not a fence-to-fence problem." Dieldrin residues in the arsenal core area, where chemical plants, waste dumps and basins for liquid toxics were concentrated, can be measured in thousands of parts per million but drop to less than 0.5 ppm a relatively short distance away. Roy emphasizes that more than 10 ppm dieldrin in a significantly large area of surface soil may pose a serious threat to wildlife.

Dieldrin disrupts the nervous system, the biologist points out. As little as 4 to 5 ppm in the brain will cause fatal convulsions in some birds and mammals. "What we don't know is how much exposure it takes to build up a lethal concentration of the chemical," Roy says. "My goal," Hoff relates, "is to determine if there are significant dieldrin-associated effects, such as mortality of adults and poor survival of cubs, among badgers that inhabit the more-contaminated arsenal sites." He is also investigating nonlethal, long-term effects, such as immune deficiency, among badgers that use highly contaminated sites.

Hoff tracks his badgers by signals from a transmitter implanted in the animals' abdominal cavities. "You can't use a radio harnessfor long-term monitoring studies of one to three years," Hoff explains. "Collars have a tendency to slip off and sometimes cause problems with irritation when exposed to soil freezing and thawing through multiple seasons of the year." Hoff captures the Rocky Mountain Arsenal's badgers in padded leghold traps, and veterinarians at the Denver Zoo perform the surgery.

The toxicologist's study is in the second of three field seasons, so his findings are still inconclusive. "I can report that badgers are using both clean sites and contaminated sites on the Rocky Mountain Arsenal," Hoff says, "and I have found surprisingly low dieldrin levels in the fat of animals from the latter areas. All the badgers we've captured have one head and four legs, and all the parts are where they're supposed to be," he jests.

J. Frank Dobie, the old yarn-spinner, might be disappointed at that news.

Les Line, former editor of Audubon magazine, wishes there were badgers to hunt the woodchucks around his Hudson Valley hideaway.


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