COLORADO SPRINGS, Colo. - For black-footed ferrets, being released in Colorado is almost a death sentence.

South Dakota is fairly safe. Wyoming is getting better all the time. But a ferret hitting the ground on the Colorado reintroduction area has only a 10 percent chance of surviving a few months.

Fortunately for them, only one of the seven adolescent ferrets being loaded into a pickup at the Cheyenne Mountain Zoo on Thursday was slated to stay in its home state.

The slender, 2-pound prairie dog hunters chattered and sniffed at the mesh on their cages as their keepers prepared to ship them to Fort Collins for a few weeks of learning to prey on live prairie dogs before they are released into the wild.

The black-footed ferret is one of the rarest creatures in North America. In 1985, there were only 18 left on Earth. Now, thanks to an extensive and costly recovery effort, there are about 1,000.

The recovery has two parts: a captive breeding program led by zoos across the country, including Cheyenne Mountain Zoo, and a program to release the animals into the wild.

Breeding starts in spring. In the fall, hundreds of ferrets are released at 11 sites in the West.

Making baby ferrets is a precise science. Lights over the cages have to be measured down to the lumen. Food has to be measured to the gram. The slightest surprise can scare the animals into not producing young.

"We're not even really supposed to talk to the ferrets," said Jeff Baughman, who oversees the ferrets at Cheyenne Mountain Zoo.

Still, they've had success. The zoo's ferrets produced 22 kits this year: 15 to keep as breeders, seven to be sent off to breed in the wild.

The wild side of recovery hasn't been as encouraging.

Ferrets eat prairie dogs. For more than 100 years, ranchers and farmers have been trying to eliminate prairie dogs.

"There just aren't that many big prairie dog towns left where we can put ferrets," said Mike Lockhart, who heads the National Black-Footed Ferret Conservation Center north of Fort Collins.

Many large prairie dog towns have sylvatic plague, a flea-borne disease introduced from Asia around 1900 that kills ferrets.

The best place for ferrets to thrive used to be a vast, plague-free swath of prairie near the Badlands of South Dakota. It had 100 breeding pairs. Survival rates were 80 to 90 percent.

Then, in 2004, federal land managers in the state gave ranchers the OK to poison prairie dogs on the site.

"If it keeps up," Lockhart said of the poisonings, "that population will go into decline."

Wyoming is now the best bet, he said. Plague is present there, but the ferrets seem to survive anyway, possibly even developing a resistance.

"We're all really surprised," said Linkhart. "Populations in Wyoming we wrote off are now going gang busters."

To come off the Endangered Species List, the population must reach 1,500 wild ferrets living in 10 locations with no less than 30 breeding adults in each colony. Currently, only about 600 black-footed ferrets live in the wild.

Colorado has not been a bright spot. Of 183 animals released since 2001, about 10 were still alive last fall. None had reproduced.

Many died within a few weeks of being released.

"We think plague is bad there," Lockhart said.

His response has been to send more ferrets where they tend to do well, and only a few to trouble spots. This year, three of Cheyenne Mountain Zoo's ferrets will go to Arizona. Two will go to Wyoming. One will go to South Dakota.

And one will go to a basin near Dinosaur National Monument in northwest Colorado.

"From there it's up to the ferrets, we don't have any control," said Baughman, who has cared for them in a sterile environment since they were the size of his pinkie. "We can just try to make sure they are healthy when they leave."