Cloning to save a polecat from extinction

The black-footed polecat has almost disappeared from the face of the Earth. Miraculously rescued thanks to the American wildlife service, this cousin of the weasel suffered from a dangerous defect, because all its representatives descend from seven polecats. The risk of congenital diseases has just been avoided thanks to a cloning program, the first in the history of conservation.

Posted at 12:00 am

Mathieu Perreault

Mathieu Perreault

Willa and Elizabeth Ann

A black-footed polecat named Willa, who died in 1988. And another named Elizabeth Ann, born in 2021, 33 years later. Few black-footed polecats are given names. But for Ben Novak, these two animals are very special. “Elizabeth Ann is a clone of Willa, explains the biologist from the American NGO Revive & Restore. We hope, through cloning, to increase the chances of black-footed polecats surviving in the wild. They were reintroduced after disappearing, thanks to a captive breeding program. But there are only seven individuals among his ancestors. So the risk of inbreeding is very high. Willa’s cloning would increase the genetic diversity of the species. »


Ben Novak holding Elizabeth Ann after her birth

Elizabeth Ann was born in early 2021, but she has a problem with her uterus that prevents her from reproducing. “We are going to do a second Willa cloning campaign this year,” says Mr. Novak. If possible, it’s because Willa’s cells were cryopreserved at the San Diego Zoo.

disappearance and rebirth


A black-footed polecat

The black-footed polecat (also called the black-footed polecat in Canada) was considered extinct in the early 1980s, but the US Wildlife Service discovered an isolated population in 1981, in Wyoming. “The last 24 individuals of this population were captured in 1987, but 6 of them died shortly after from a virus,” says Novak. Wildlife biologists managed to raise 14 of the 18 survivors in captivity. But due to inbreeding, there were actually only seven different individuals with the original lineage in captivity. »

“In the early 1990s, we began to reintroduce black-footed polecats to states from which they had disappeared,” continues the biologist. We still maintain the captive breeding program, because most populations are not capable of sustaining themselves. This is how we add animals born in captivity to the populations that need them. Willa is one of six black-footed polecats captured in 1987 that died from a virus before they could breed in captivity.

There are no black-footed polecats in countries other than Canada and the United States. The black-footed polecat has disappeared due to urbanization, which has also affected its main prey, the prairie dog. In Canada, the Toronto Zoo participates in the United States captive breeding program for the black-footed ferret.

The abc of cloning


Elizabeth Ann at 4 months

Revive & Restore takes a pet ferret egg and removes all reproductive genetic material. A few Willa cells are inserted into the pet ferret’s egg. The clone is then on its way. In the first round of cloning, five clones were successfully implanted into female domestic ferrets, but only Elizabeth Ann was born.

Why not use a black-footed polecat from the captive breeding program as a surrogate mother? “Because there are only 150 individuals in the program and we still need them to revive wild populations,” says Novak. The enucleated domestic ferret egg contains some genetic material, the “mitochondrial” DNA. But the amount of DNA in the mitochondria of the egg cell is 100,000 times less than the total DNA of a cell. So it doesn’t contaminate the black-footed polecat genome, says Novak.

The passenger cake


The homing pigeon, drawn by the American naturalist Jean-Jacques Audubon in the 19th century

The other project that Revive & Restore puts a lot of energy into is the cloning “de-extinction” of the homing pigeon, which gave the tourtière its name (and disappeared over a century ago). “We would start with the eggs of a common pigeon, from which we would remove the genetic material and replace it with genes from biological samples of racing pigeons that have been well preserved,” says Novak. But there are still some steps in the ethical approval of the project. »


Homing pigeon hunting with a net, according to the British illustrator James Patisson Cockburn (1779-1847)


Louisiana passenger pigeon hunting in 1875, according to British magazine illustrator Bennett Smith Illustrated sports and drama news

The carrier pigeon was considered the most abundant bird species in the world when America was discovered. The last specimen, Martha, died at the Cincinnati Zoo in 1914. Jacques Cartier mentioned the abundance of the homing pigeon as early as 1534 when he stopped at Île Saint-Jean, now Île-of Prince Edward Island. Hunting was the death knell for the carrier pigeon in the 19th century.

The mountain goat and the mammoth


Celia, the last mountain goat of the Pyrenees, has been stuffed.

Cloning is the dream of specialists in extinct species. In 2003, an American gene therapy company, Advanced Cell Technologies, tried unsuccessfully to clone Celia, the last Pyrenean ibex, captured in 1999 and killed in captivity. Celia’s clone, made from a cryopreserved skin cell of hers, died within minutes of her birth due to a malformation in her lungs.


Artistic representation of a mammoth

“The project that most captures the public imagination is the ‘de-extinction’ of the mammoth,” says Novak. In this case, we would start from elephant eggs. The Californian biologist published in 2018 a list of a dozen animals that could be subject to “desextinctions”, in the magazine Genoa.

Texas Cougar and Florida Panther


the flowery panther

At least one other species has been saved from inbreeding. This is the Florida panther, saved from congenital diseases by the arrival of eight female cougars from Texas in 1995. “There were only about 30 Florida cougars left,” says Mr. Novak. Many suffered from undescended testicles. But obviously, at the time, we weren’t talking about cloning. The Texas cougar is a close cousin of the Florida panther, but is a different species. With our approach, we will preserve the genetic makeup of the black-footed polecat. »

florida vaquita


a little cow

Inbreeding is not a disaster for all species. In June, biologists noted that the world’s rarest cetacean, a porpoise called the vaquita, has probably had the same number of individuals for several decades. “There are only about 10 vaquitas, a species that has been trapped for tens or hundreds of generations in the northern Gulf of California,” says Jacqueline Robinson of the University of California, San Francisco, who is the lead author of the published study. in Sciences.


A California Condor

“We have never reported vaquitas anywhere else on the planet. They are caught in fishermen’s nets and their population has decreased throughout the 20th century. His secret is an innate ability to suppress dangerous genetic mutations. Other species that have survived a very small number of individuals may have the same capacity for genetic suppression, suggests the Californian biologist. “The California condor only had about ten individuals in zoos in the late 1980s when it was reintroduced into the wild. Now there are 500 in the wild. »

More information

  • 1000
    Number of black-footed polecats in the wild in the United States and Canada

    SOURCE: Revive & Restore

    Number of distinct populations of black-footed ferrets in the wild in Canada and the United States

    SOURCE: Revive & Restore

  • 4
    Number of black-footed polecat populations that no longer require inputs from the species reintroduction program

    SOURCE: Revive & Restore

    30 to 50
    Number of black-footed polecats added to wild populations each year through the captive breeding program

    SOURCE: Revive & Restore

  • 500,000 to 1 million
    Estimated number of black-footed polecats in the early 19th century

    SOURCE: Revive & Restore

    3 to 5 billion
    Estimated number of homing pigeons in the 18th century

    SOURCE: Revive & Restore

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