CPW releases 14 of the rarest mammals in North America

An endangered black-footed ferret surveys its new home on Walker Ranch west of Pueblo West after it was released from a captive-breeding program designed to restore the rarest mammal in North America.


PUEBLO WEST, Colo. – Fourteen endangered black-footed ferrets were released in a prairie dog colony on the Walker Ranch Nov. 18 as part of a decades long effort by Colorado Parks and Wildlife, U.S. Fish and Wildlife Service (USFWS) and other partners to restore the rarest mammal in North America.
The black-footed ferret is the only ferret species native to North America and twice was thought to be extinct due to habitat loss, widespread poisoning of prairie dog colonies and disease.
The last official record of a wild black-footed ferret in Colorado was near Buena Vista in 1943. Then in 1979, the last known black-footed ferret in captivity died, and the only ferret species native to the U.S. was believed to be lost. Since 1967, black-footed ferrets have been listed as endangered under the federal Endangered Species Act.
But in 1981, a small colony or remnant population, of 129 ferrets was discovered on a ranch near Meeteetse, Wyoming. This population, however, soon experienced significant declines due to canine distemper and sylvatic plague. So in 1986, the USFWS captured the remaining 18 wild ferrets for a captive breeding and species preservation program. Those ferrets became the seed population for all subsequent captive breeding and recovery efforts.
CPW joined forces with USFWS, the Utah Division of Wildlife Resources and the Bureau of Land Management (BLM) to restore black-footed ferrets to their native range. Today, Colorado is one of eight states involved with the recovery of the species through reintroduction.
Ferrets were first reintroduced to Colorado in 2001 at Wolf Creek, north of the town of Rangely. After dozens were released over several years, that site succumbed to a plague outbreak and collapsed by 2010.
An Eastern Plains reintroduction strategy began in 2013 with the release of 300 ferrets to six Colorado sites. In order to be released, individuals have to display their ability to survive in the wild. This training and preparation takes place at the National Black-Footed Ferret Conservation Center in Larimer County.
So far, 254 black-footed ferrets have been released on the private lands enrolled in the Safe Harbor Agreement (SHA) program. Most were raised in captivity at special breeding facilities.
The restoration of any threatened or endangered wildlife species is deemed successful when released animals begin reproducing on their own in the wild. Black-footed ferrets mate in early spring and give birth to a litter of three or four mouse-sized kits after a seven-week gestation period.
“Our goal is to create conditions where we have a self-sustaining population of ferrets and captive-born ferret releases are no longer necessary,” said Ed Schmal, CPW conservation biologist. “To do this, we need to maintain healthy prairie dog populations and implement annual plague management.”
CPW biologists can’t know for sure whether black-footed ferret reintroduction efforts can be deemed a “success.” But biologists found a hopeful sign with the first wild-born kit, or baby ferret, in 2015 and more after that.
Much of CPW’s current work focuses on plague management to ensure continued persistence of the ferrets and prairie dogs they rely on. Continued ferret reintroduction efforts seek to increase genetic diversity at each site.
On Monday, CPW released 10 juvenile and 4 adult ferrets into prairie dog burrows on the nearly 80,000-acre Walker Ranch outside Pueblo West. The ranch is owned by Gary and Georgia Walker, who are pioneers in creating safe harbors for ferrets on private land.
Since 2013, 107 black-footed ferrets have been released on Walker Ranch by CPW biologists, who have invested extensive time and effort to monitor the colonies and distribute plague vaccine across the vast colonies in hopes of protecting the black-footed ferrets and the prairie dogs, which is their primary source of food.

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