Contributing Editor Jordan Schaul interviews black-footed ferret wildlife biologist Heather Branvold of the US Fish & Wildlife Service (USFWS). The Black-footed Ferret Recovery Program is celebrating the 30th anniversary of an effort to restore to the wild what was once the most endangered terrestrial mammal on Earth.
What is more emblematic of a conservation icon than a giant panda cub or a bull African elephant? Immediately recognizable, these particular species epitomize charismatic megafauna. Common figureheads in conservation marketing campaigns, giant pandas and elephants have been recruited, for years now, to help to save vanishing habitat and ultimately themselves. Hopefully, Chinese bamboo forests and African forests and savannas will benefit from these branded flagship species.
In North America, the American bison, another keystone species which once roamed and shaped the landscape of much of the Great Plains, still survives in much smaller, heavily managed herds. These grazing herbivores–the largest land mammals in the Western Hemisphere–kept the grasslands in check and created microhabitats for a host of other prairie-dwelling species.
Although efforts ensue to restore both plains and wood bison subspecies to parts of their historic range, the real success story from the prairie, and North America, for that matter, involves a small and secretive member of the weasel family. This fossorial mustelid is endemic to the shortgrass prairie ecosystem of the Great Plains. Although small in stature and elusive, the black-footed ferret, is no less charismatic than the panda, elephant or bison. It has character, a lot of it and it’s story is exemplary.
Once, the rarest mammal on Earth–the comeback kid was actually thought to be extinct. Its restoration is a testament to a 30 year long recovery effort of US federal and state agencies, and nonprofit organizations including zoological parks.
Dr. Schaul: As we look back on 30 yrs, what milestones should we be most proud of regarding this conservation effort?
Dr. Branvold: The first kits were born in captivity in 1989. Since then, we have produced over 7600 ferrets. Captive breeding is a real success story in helping to recover the black-footed ferret. There is always more to learn, but we now know how to produce ferrets in captivity for release into the wild.
This is also the 20th anniversary of reintroduction. Black-footed ferrets were extirpated from the wild in 1987. In 1991, the first ferrets were released back into the wild in Shirley Basin, WY. We now have a total of 19 reintroduction sites, and release 150-250 ferrets per year. The wild population is estimated to be about 1000.
Dr. Schaul: What makes the black-footed ferret so charismatic?
Dr. Branvold: Being related to domestic ferrets, black-footed ferrets have many of the same playful characteristics such as the “ferret dance” & playing in the water dish, but yet they retain their wild behaviors. They definitely have the cute factor going for them, but they will defend themselves fiercely and are able to kill prey almost twice their size.
They are unique in being the only ferrets native to North America.
Dr. Schaul: The ferrets prey base consists largely of prairie dogs. They are pretty charismatic in their own right, but they, too, have struggled. How would you characterize their future and ultimately the black footed ferret population which is so dependent on them?
Dr. Branvold: Black-footed ferrets cannot survive without prairie dogs. They rely on them for food as well as shelter (prairie dog burrows). In order to recover the black-footed ferret, we must conserve some prairie dog habitat. Sylvatic plague is a disease that is fatal to both ferrets and prairie dogs, and is currently one of the largest obstacles to black-footed ferret recovery. We are currently working on an oral plague vaccine for prairie dogs and an incentive package to encourage landowners to retain prairie dogs and their habitat. We are confident the black-footed ferret will someday be recovered!
Dr. Schaul: I’ve only seen captive ferrets. The breeding programs have played a significant role in saving this species. Can you talk about the consortium of facilities that have been involved in this restoration effort on the captive side?
Dr. Branvold: We currently have six captive breeding facilities: The National Black-footed Ferret Conservation Center (NBFFCC) (Colorado), Cheyenne Mountain Zoo (Colorado), Louisville Zoological Garden (Kentucky), National Zoo’s Smithsonian Conservation Biology Institute (SCBI) (Virginia), Phoenix Zoo (Arizona), and Toronto Zoo (Ontario, Canada). The Henry Doorly Zoo (Nebraska) participated in captive breeding until the late 1990’s.
The NBFFCC is run by the US Fish & Wildlife Service. It houses the majority of captive black-footed ferrets. There are also outdoor pens here for preconditioning ferrets (giving them access to natural burrows and live prairie dogs prior to release into the wild).
The zoos have played a critical role in captive breeding, allowing us to have ferrets in multiple places in case diseases/etc were to occur at one facility. Artifical insemination, cryopreservation, and genome resource banking at SCBI have helped to minimize the loss of genetic diversity.
Dr. Schaul: As a veterinarian and restoration biologist you are well equipped to address the animal health aspects that have plagued reintroduction efforts for this species. Can you talk about conservation medicine as it has applied to the return of what was historically refereed to as the most endangered mammal in North America and the World?
Dr. Branvold: Black-footed ferrets are susceptible to a variety of diseases. Canine Distemper Virus (CDV) was found in the population that was discovered in 1981. The virus is almost 100% fatal, and at the time believed to be the reason for that population’s decline. We now know that sylvatic plague is a huge problem. It is a foreign disease that neither prairie dogs nor ferrets have much (if any) resistance to. It is likely that plague also played a role in the original population’s decline.
Standard CDV vaccines used in domestic animals are fatal to black-footed ferrets. This is probably due in part to a compromised immune system, likely from years of inbreeding. However, we now have a safe and effective vaccine against CDV for black-footed ferrets. All ferrets released into the wild receive this vaccine, and some reintroduction sites vaccinate wild-born ferrets, as well. Although outbreaks of CDV occur in the wild, it no longer remains as much of a threat as it once was.
Sylvatic plague is a different story. Thanks to the National Wildlife Health Lab and the US Army, we do have a safe and effective vaccine against plague in black-footed ferrets. Again, all ferrets released receive this vaccine and several reintroduction sites vaccinate wild-born ferrets. However, unlike CDV, vaccinating ferrets alone is not enough to combat plague. Prairie dogs also succumb to the disease, and it often wipes out whole colonies. Even if ferrets are vaccinated, if there is no food (prairie dogs) they will also die. We are currently working on an oral plague vaccine for prairie dogs. The initial trials gave very encouraging results.
(Photos–Courtesy of USFWS)