Several Utahns have reported seeing black-footed ferrets in the state during recent years. But if anyone can document such a sighting, it is worth $5,000, the state Wildlife Resources Division says.

The endangered mammals were once native to Utah, the division said Tuesday. But now the only known remaining U.S. population of black-footed ferrets - 62 animals - is in Wyoming.A 1985 outbreak of canine distemper in the last known wild population wiped out all but a tiny remnant of the Wyoming ferrets, leaving as few as 18 of the mammals, said Denise Knight, a division non-game biologist.

The 18 remaining ferrets were captured to form the nucleus of a breeding project. But the U.S. Fish and Wildlife Service is looking for any others that may have survived in the West because the animals in the captive population are believed to be "closely related."

The ferrets live only in prairie dog towns and apparently eat only prairie dogs. They are buckskin in color, Knight said, with a darker patch on the back, lighter fur on the face, chest and stomach, and black patches across the eyes and on the feet, legs and on the tip of the tail.

The $5,000 reward offered by the U.S. Fish and Wildlife Service runs through Sept. 30, 1989. It will be paid to anyone who provides a photograph of a black-footed ferret or information that results in verification.

The ferrets, which grow to about 20 inches in length, have always been considered relatively rare in Utah, Knight said, but the federal agency hopes to find a few of the animals to improve the gene pool in the captive population.

Lou Hanebury of the service's National Ecology Center, Fort Collins, Colo., said a combination of factors wiped out the ferrets, including a poisoning program in the 1920s and `30s to eradicate prairie dogs from livestock grazing lands, followed by distemper and plague.

"There still could be a few out there, especially in Wyoming, but we don't know," said Hanebury.

The last black-footed ferret captured in Utah was in 1937, near Blanding. And the state's last recognized sighting was in the early 1980s, near Westwater Canyon along the Utah-Colorado state line.

The most serious problem facing the captive population, Hanebury said, is that all of the surviving kits born in 1987 and this year "are derived from seven ferrets related to each other."

The service "has not seen any bad effects yet from inbreeding, but that is a concern," he said. "That's the reason for the reward."