"[T]his plane extends with the same bredth from the creek below to the distance of near three miles ablove parrallel with the river, and it is intirely occupyed by the burrows of the barking squiril heretofore described. . . . a great number of wolves of the small kind, [hawks] and some pole-cats were to be seen. I presume that those anamals feed on this squirril." --Meriwether Lewis
As the group headed to the Upper Missouri River, Lewis took a day to stretch his legs and explore the new landscape. In this country of deep ravines and open plains, he noticed acres of prairie dogs poking out of their burrows. Predators waited for their chance at a prairie-dog meal, most hiding in the grass or circling overhead, others lurking underground.
Spending much of the day out of sight below the soil surface, the black-footed ferret wasn't described until the naturalist John James Audubon wrote about it in 1851 (though Lewis recorded seeing "pole cats," which may have been a reference to the ferrets).
No one else commented on the ferrets for another 26 years. But the animal's elusive nature didn't keep it out of trouble. The lithe creature with a black bandit mask was destined to become one of North America's most endangered mammals.
The lives of the black-footed ferrets are intertwined with their main prey, the black-tailed prairie dog. Historically, prairie dogs made up 90 to 95 percent of their diet. A ferret can eat a prairie dog every three or four days, no small feat as the animals are roughly the same size. The ferrets spend much of their lives in prairie-dog burrows, using them to hide from hawks and coyotes, and giving birth and raising their young in the tunnels. (From a prairie dog's perspective, the ferret is a very ill-behaved guest.)
Possibly descended from Siberian polecats that crossed the Bering Strait land bridge during the last ice age, ferrets belong to the weasel family. They are nocturnal, solitary hunters, sometimes ranging over 100 acres of territory. Because they are so elusive, little is known about their habits.