For the first time in almost 30 years, Arizona Game and Fish Department (AZGFD) biologists performed a re-introduction of ten endangered black-footed ferrets to the once-flourishing Aubrey Valley/Double O Ranch area, attempting to re-populate the only active recovery spot in Arizona.

The ferret kits were captively bred at one of six sites across the country, including the Phoenix Zoo. The kits were then taken to the U.S. Fish and Wildlife Service’s National Black-Footed Ferret Conservation Center in northern Colorado, where they learned to hunt and live in the wild.

Readying the Aubrey Valley for this reintroduction has been a years-long process. After seeing great recovery success in the early 2000s, the ferret population peaked at 123 members in 2012. Since then, the population has been on a steep decline.

“We couldn’t begin to re-establish this population without understanding the ferret die-off,” said Holly Hicks, AZGFD’s senior small mammal management specialist.

Sylvatic plague, a bacterial disease, is one of the biggest threats to black-footed ferret recovery, infecting both the ferrets and their main prey, Gunnison’s prairie dogs. But after walking transects across the Aubrey Valley, totaling about 400 miles, biologists saw no signs of plague, only multiple healthy prairie dog colonies.

So in 2017, biologists began a three-year telemetry study. Ferrets were fitted with collars and monitored to see where they went after they were released. The results were clear - ferrets follow prairie dogs.

“It was starting to become obvious that it was a prey base issue,” said Hicks. “So in 2020, we switched to a disease treatment study of the prairie dogs.”

The results of the study were surprising: Sylvatic plague was to blame, but the prairie dogs survived year to year with it, something biologists hadn’t seen in Arizona before. Black-footed ferrets, however, are extremely susceptible even to low levels of plague.

“Now we’re targeting the fleas that transmit plague between the prairie dogs and ferrets,” said Hicks. “We’re treating the prairie dogs with the same active ingredient that's in dog and cat flea medicine.”

With the plague under control, biologists could plan the re-introduction. Choosing areas of highest prairie dog population as well as those with the longest and most effective flea treatment history, biologists were able to release the ten ferrets, each with a little chunk of prairie dog snack to send them on their way. The ferrets were also “chipped” with a passive integrated transponder - a PIT tag - just like pet dogs and cats get. All ferrets were also vaccinated for plague prior to release.

Along with the PIT tags, on-the-ground monitoring will continue. The first spotlighting event to check in on the ferrets happened at the end of October and four of the ferrets were found doing well.

Ferret releases will continue for the next three years during both fall and spring, allowing biologists to collect data like prairie dog densities, seasonal patterns, and more. Biologists will also continue disease treatments and vaccinations.

The public can help AZGFD biologists with black-footed ferret recovery. When spotlighting and monitoring volunteer opportunities are available, they will be posted at volunteer.azgfd.gov.