New digs for the ferret? A multinational program to introduce an endangered species into Northeastern Mexico may stimulate future cooperative conservation projects across borders.

• Author: Cohn, Jeffrey P.

The last rays of daylight were rapidly fading into night over the Chihuahuan grasslands last fall as wildlife biologist Rurik List reached down and opened the door to one of several pet-carrying cages. Within moments, a black-footed ferret poked its head out, gazed across the seemingly endless prairie dog towns that dot the flat valley west of the Janos-Nuevo Casas Grandes region of northeastern Mexico, and suddenly dashed for the safety of a nearby burrow. Perhaps befitting the mystery that has long surrounded the species, the black-footed ferret was gone almost as suddenly as it had appeared.

In all, List, an associate researcher at the National Autonomous University of Mexico's Institute of Ecology, and other wildlife biologists from Mexico and the United States released a hundred black-footed ferrets in the Janos region on four different occasions last fall. The animals, almost all born earlier in 2001, came from captive-breeding facilities in the United States and Canada. The releases are part of a $1.5-million-a-year, multi-agency and multinational effort to save black-footed ferrets from extinction and restore them to the wild. If the Janos release works, it could help revive a ferret restoration program that has run into problems in the United States. It could also have far-reaching implications for wildlife conservation in Mexico and for joint U.S.-Mexican programs along both sides of the border.

"This is an extremely important area for us in Mexico," says Gerardo Ceballos, professor of ecology and conservation at the National Autonomous University of Mexico in Mexico City. "This is the last large grassland in Mexico. Grasslands are endangered ecosystems throughout North America. The black-footed ferrets will help us preserve that ecosystem and all the species that depend on it."

Black-footed ferrets are long, slender animals with short legs. They are relatives of weasels, badgers, skunks, and otters. The only native North American ferret, black-footed ferrets are closely related to Asian ferrets. The common domestic ferret is descended from the European ferret, or polecat. Fully grown, black-footed ferrets measure twenty to twenty-four inches long and weigh only two or three pounds. With a black face mask, black feet, and a black-tipped tail that contrast sharply with their tawny bodies, the ferrets resemble masked marauders.

Little known, rarely studied, and seldom seen, black-footed ferrets are usually active only at night, spending most of their time hidden in underground burrows. As a result, they remained unknown to science until "discovered" by naturalists John James Audubon and James Bachman in 1851. The ferrets once ranged from southern Canada into Texas and from the eastern slopes of the Rocky Mountains across the Great Plains. They could be found virtually everywhere on the prairies where there were prairie dogs, squirrel-like rodents that once lived in huge communal towns from Canada to Chihuahua in Mexico.

Today, as then, black-footed ferrets depend on prairie dogs for food and shelter. At least 90 percent of a wild ferret's diet consists of prairie dogs. The nimble ferrets not only dine on the rodents, they also appropriate their unwitting hosts' burrows for their own use. Unfortunately, ranches, farms, and cities are often located where prairie dog towns once thrived. Further, ranchers and farmers in the U.S. West often view prairie dogs as vermin that compete with cattle and sheep for grass and whose diggings leave horses lame While scientists dispute those claims, they have led to government and private programs to eradicate prairie dogs. Poisoned, shot, and trapped, prairie dogs now occupy only 1 or 2 percent of their estimated 100 million acres in the United States a century ago.

As prairie dogs went, so, too, did black-footed ferrets. Probably never common, the ferrets were long considered one of the rarest of North American mammals. They were feared extinct in the 1960s and again after a rediscovered population in South Dakota disappeared mysteriously in the 1970s. Then, some 120 ferrets were found near Meeteetse in...