Black-Footed Ferrets: Back from the Brink

Bff = black footed ferret

Giving some love to a BFF (Black-Footed Ferret).

Today is Valentine’s Day (February 14) and our thoughts turn to doing something special for a significant other (so),  a best friend (bf) or best friend forever (bff).  In this blog we consider doing something special for a bff, but the bff at focus here is not human.

This bff is the black-footed ferret.

That’s correct—we’re talking about the weasel-like critter with the black mask, black tail tip and black feet. This small, wiry animal, with the help of some particularly dedicated humans, has had an amazing come-back story since the 1970s, when these ferrets were believed to be extinct.

About the BFF (Black-Footed Ferret)
The black-footed ferret, Mustela nigripes, is a member of the family Mustelidae, which includes mink, badger, marten, fisher, polecat and wolverine (of course domestic ferrets are also members of this family). Like mink and other members of the mustelidae, bff are long, slender animals that average 18 to 24 inches in length. Black-footed ferrets weigh 1½ –2½ lbs. Female ferrets are “jills”, males are “hobs” and juvenile ferrets are “kits”. The average life span of a black-footed ferret in the wild is 1–3 years.

Adult black footed ferret.

Adult black-footed ferret. Credit: J. Michael Lockhart / USFWS. This image is the work of a U.S. Fish and Wildlife Service employee, taken as part of that person’s official duties. As a work of the U.S. federal government, the image is in the public domain.

Habitat
Black-footed ferrets are native to central North America and found only on this continent mainly in the western and southwestern US.

The BFF Problem?
Food source and habitat are tied in a complicated package for this tiny weasel. Black-footed ferrets exist in open grasslands and subsist almost exclusively on prairie dogs, who also make grasslands their home.

Prairie dogs are known to carry the plague bacterium, Yersinia pestis. This is the bacteria responsible for the Black Plague that killed millions of people along the trade routes from China to Europe beginning in about 1300. An earlier plague pandemic is estimated to have killed 25 million people around 541AD, and there have been subsequent pandemics with many millions of deaths globally, extending into the 20th century. Yersinia pestis is a deadly pathogen.

The culprit for such successful transmission of plague bacteria is the flea, which bites rodents (historically rats which carry plague bacteria), then bites and spreads the bacteria to humans.

Why plague bacteria seem to exist in prairie dogs with low or no mortality at times, and with very high mortality at other times, is currently not well understood, but during prairie dog endemic plague, entire villages can be wiped out. Some plague episodes with a high prairie dog mortality may be connected to particular weather conditions, but the phenomena affecting plague bacterium mortality is currently not well understood and in need of more research.
You can find a wealth of plague information at the Centers for Disease Control web page.

In addition, this blog, promegaconnections.com has seen a number of well-written blogs on various aspects of plague, including modern and recent incidents.

What is known is that plague kills black-footed ferrets and their main source of food, prairie dogs.

Another problem for black-footed ferrets is that grasslands are becoming more and more popular for cattle grazing, adding pressure to both prairie dogs and black-footed ferrets by decreasing the size of available habitat. Furthermore, it is legal in a number of western states to hunt prairie dogs. What’s bad for the prairie dog is bad for black-footed ferrets.

Black-Footed Ferret Extinction-Almost
According to the Wikipedia page on the black-footed ferret :

“It was declared extinct in 1979 until Lucille Hogg’s dog brought a dead black-footed ferret to her door in Meeteetse, Wyoming in 1981. That remnant population of a few dozen ferrets lasted there until the animals were considered extinct in the wild in 1987. However, a captive breeding program launched by the United States Fish and Wildlife Service resulted in its reintroduction into eight western states and Mexico from 1991 to 2008.”

Upgrade to Endangered
In 2008, the black-footed ferret was upgraded to the endangered species list. The US Fish and Wildlife Service black-footed ferret reintroduction program has been successful, with an estimated 1,000 wild-borne adult ferrets in South Dakota and Wyoming, these efforts are on-going to increase bff populations.

Plague Interruption Program
Several efforts have been used to interrupt the plague cycle in prairie dogs. Flea-killing dust has been sprinkled at the entrance to prairie dogs burrows. Spreading of insecticidal dust is of course a time- and labor-intensive process that can be interrupted by certain types of weather.

A human plague vaccine was previously used by the US military. This vaccine is not currently in production for humans, but has been found effective for prairie dogs. How do you vaccinate a prairie dog? Apparently peanut butter is irresistible to them, and clever individuals have devised a vaccine-in-a-cookie using peanut butter. These tasty pellets can be dropped by helicopter over prairie dog villages, and the edible vaccination has been shown to protect prairie dogs later exposed to plague bacteria.

Some black-footed ferrets that were bred and raised in captivity have been successfully vaccinated by injection against plague, but this practice doesn’t work well for wild populations. And you’ll recall that black-footed ferrets eat prairie dogs almost exclusively: no peanut-butter-vaccine-cookies for ferrets.

Creating a Better Black-Footed Ferret?
A somewhat more 21st century idea has been proposed to help strengthen and ensure recovery of black-footed ferret populations. An initiative called Revive & Restore has been created by Stewart Brand and friends. The Revive & Restore plan is essentially to use modern-day genetic engineering capabilities to bolster populations that are threatened, by improving the genotype of the affected species.

Brand visited Promega in Madison, WI recently and talked about the Revive & Restore and efforts to save, protect and even re-establish a variety of plant and animal species that are facing crisis worldwide. Included on the list is the black-footed ferret.

In the case of black-footed ferrets, the small number of ferrets available for breeding to re-establish bff in the wild resulted in inbreeding. Inbreeding can caused decreased genetic vigor, higher incidence of genetic abnormalities in offspring and even lower number of kits.

According to the Revive & Restore website:

“In 2013, Revive & Restore was invited by the U.S. Fish & Wildlife Service to explore the potential use of genomic technologies to increase the genetic diversity” of black-footed ferrets. The genomic techonology under consideration is the use of interspecies somatic cell nuclear transfer (iSCNT) to try to increase genetic diversity in bff. “

This 2015 paper from the Journal of Heredity explains the plan that scientists, working with Revive & Restore propose: “A Road Map for 21st Century Genetic Restoration: Gene Pool Enrichment of the Black-Footed Ferret”.

Simply, somatic cell nuclear transfer (SCNT) can be used to clone individuals without taking genetic material from a germ cell. Instead, nuclear DNA content can be collected from another cell type, such as skin cells. The authors of this paper suggest performing the DNA transfer technique using material from non-native domestic ferret.

This work is a really interesting proposal for how SCNT and DNA from domestic ferrets could make a better ferret. This work requires permission by the USFWS and other federal agencies.

Bff dancing

BFF doing the weasel war dance. Credit: J. Michael Lockhart / USFWS- Jumping Black-footed Ferret, This image is the work of a U.S. Fish and Wildlife Service employee, taken as part of that person’s official duties. As a work of the U.S. federal government, the image is in the public domain.

One final note on BFF. As a fan of prairie dogs and their highly social, family-oriented lifestyle, it’s taken me a little while to warm up to black-footed ferrets and their prairie dog-consuming lifestyle. If you feel this way as well, here is a video that will help you “warm up to” the black-footed ferrets. This video features a young black-footed ferret in the wild ‘doing the weasel war dance’.

Want to Get Involved?
You can get involved and become a Friend of Bff. See the website for details.

 

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Kari Kenefick

Kari has been a science writer/editor for Promega since 1996. Prior to that she enjoyed working in veterinary microbiology/immunology, and has an M.S. in Bacteriology, U of WI-Madison. Favorite topics include infectious disease, inflammation, aging, exercise, nutrition and personality traits. When not writing, she enjoys training her dogs in agility and obedience. About the practice of writing, as we say for cell-based assays, "add-mix-measure".

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