ENDANGERED SPECIES -- Biologists and wildlife officials have released 18 black-footed ferrets on the Crow Reservation in Montana.

The Billings Gazette reports that a convoy of vehicles brought the endangered ferrets into the heart of Crow Country, where they were released near a prairie dog town spread across a hillside.

Officials released 29 of the ferrets on the 5,000-mile Crow Indian Reservation last year, but only a few survived.

There must be 10 back-footed ferret populations with at least 30 breeding adults for the animal to be removed from the endangered species list.

The ferrets have suffered from environmental changes, habitat fragmentation and losses of prairie dogs, the ferret's main prey.

The Crow release site is 26th in the nation since 1991 and the sixth tribal location. The ferrets have also been released at Fort Belknap Indian Reservation in north-central Montana, the Charles M. Russell National Wildlife Refuge and the U.L. Bend Wilderness.