50 years ago this month, President Richard Nixon signed the Endangered Species Act into law.

One of the first on the endangered list the black footed ferret, North America's rarest animal.

It was once thought to be extinct.

But thanks to the dedicated work of conservationists, it's making its way back.

We went to see some of that work for this report part of our ongoing series Saving Species.

JOHN YANG (voice-over): There is a lot riding on these squirming, squeaky newborns.

They're black-footed ferrets, and whether they thrive will go a long way in determining whether their species will survive.

ADRIENNE CROSIER, Smithsonian Conservation Biology Institute: The life of the ferret has a lot of pressures out in the wild their flagship North American carnivore species.

They absolutely have a critical role to helping maintain the balance of the ecosystem.

We try to look at each individual kit every day if we can.

JOHN YANG (voice-over): Adrienne Crosier is in charge of the breeding program at the Smithsonian Conservation Biology Institute.

Her goal is to produce enough of this rare member of the weasel family to help stop breeding programs around the country and reintroduce them into the wild.

ADRIENNE CROSIER: Every enclosure either has a single adult or a family group.

So for example, this is stink pot, and she has seven babies.

JOHN YANG (voice-over): We visited cruiser during the birthing or wellbeing season.

She introduced us to all ages of baby ferrets which are called kits.

JOHN YANG: You can see some of them peeking out.

ADRIENNE CROSIER: Yeah, they're peeking out.

They're getting really big now and they already look like little adult ferrets.

JOHN YANG: And I was thinking about not coming up because she wants to protect the kits.

ADRIENNE CROSIER: So that's her box.

That's her territory.

She keeps all the kits in there.

JOHN YANG (voice-over): Each day the staff carries out a carefully choreographed routine to separate the kits from their mothers for inspection.

After they've been checked out and placed in a fresh clean box -- ADRIENNE CROSIER: I'm going to pick it up.

And she just goes right back into.

JOHN YANG (voice-over): The kits to return to their mothers who sometimes give the caretakers a piece of their mind.

We help check out series six kits just a few weeks old.

They're unable to see until they're about 35 days old.

ADRIENNE CROSIER: So we just look at them each every day to make sure that everything looks normal, their eyes look normal, there's no swelling or scabenous (ph) or crustiness around the eyes.

Make sure everybody is nice and vigorous.

He's going to seem very sleepy.

JOHN YANG: Is just curling up to go back to sleep.

JOHN YANG (voice-over): When it was over, this mother quickly moved her kits from one box to another doing her own maternal headcount.

Nestled in the foothills of the Blue Ridge Mountains the conservation campus in Front Royal Virginia uses reproductive technology to breed species for cheetahs to black footed ferrets.

Crosier says the ferret size requires them to do some improvising.

ADRIENNE CROSIER: Because they are so very small.

We really have challenges finding tools and instruments that we can use on what may be only a seven or 800 gram female.

So we have to get really creative, and we've bought some special tools that are actually made for pediatric surgery so that we can try to improve our success in artificial insemination and the species.

JOHN YANG (voice-over): Black-footed ferrets were first put on the endangered species list in 1967.

And then in 1979, when the last known member of the species died in captivity, they were declared extinct.

But two years later came a surprising discovery.

Made by a Wyoming ranch dog named Shep, he took a dead black-footed ferret home to his owner that led to the discovery of 24 black footed ferrets alive and well in Northwest Wyoming.

All members of the species known today are descendants of that group.

PAUL MARINARI, Smithsonian Conservation Biology Institute: This is one of the kind of historic mementos representing the pedigree of the first couple of years of black-footed ferrets in the breeding program.

JOHN YANG (voice-over): Paul Marinari knows the family tree like the back of his hand all the way back to the original mom.

PAUL MARINARI: Actually, that is Mama Bear.

You can see the reason why she was called mom -- JOHN YANG: Right.

PAUL MARINARI: -- because this was a litter that she had in the wild.

So when she and her offspring were captured from the wild, we had to make certain assumptions of who the dad was, that is Scarface and he was actually the last black-footed ferret to be captured.

He was quite prolific when it came to breeding very over represented in the population.

JOHN YANG (voice-over): Marinari is the keeper of the Smithsonian's black-footed ferrets studbook.

PAUL MARINARI: We can also just do an overall body check.

JOHN YANG (voice-over): Most of his career has been spent studying the species.

For 16 years he was director of the U.S.

Fish and Wildlife Service's Black-Footed ferret Conservation Center in Colorado.

PAUL MARINARI: We have a very stable breeding population around 300 individuals.

The wild population is precarious in places.

There are several populations that are doing really well.

And we estimate that there's between three and 400 black-footed ferrets living in the wild.

It's kind of the perfect species to deal with a breeding program and a reintroduction program.

They don't live that long.

They are very quick to produce offspring.

They produce a fair number of offspring.

That's the simple version.

Saving the species is much more complex.

JOHN YANG (voice-over): That complexity comes in part from the black-footed ferrets relationship with Prairie dogs, which make up 90 percent of their diet.

ADRIENNE CROSIER: They require prairie dogs to thrive.

They require prairie dogs for their burrows for their homes.

And also it's their primary price wars.

The prairie dogs are not very popular with the farmers especially because they do so much damage to the farmland.

And so the prairie dogs are actively removed from farmland which means the ferrets don't have a home the ferrets don't have prey.

JOHN YANG (voice-over): Prairie dogs are a keystone species the glue that holds a habitat together.

But many ranchers and farmers in the West consider prairie dogs pests to be eliminated.

In the early 1900s widespread poisonings were commonplace.

JOHN YANG: If you don't have prairie dogs, you won't have ferrets.

And if you don't have ferrets -- ADRIENNE CROSIER: So it's a balance, and they're all occurring naturally.

And they should all be occurring naturally, and keeping each other in balance.

But if you take out one piece of that, which is usually caused by humans, then everything falls out of balance.

And then we have complete loss of species.

But anytime you have an extinction event like that caused by human intervention, obviously we're doing something really catastrophic to the ecosystem.

JOHN YANG (voice-over): The prairie ecosystem once covered 1/3 of North America stretching from Canada to Texas, but since the late 19th century, it's shrunk by 62 percent.

PAUL MARINARI: We can save the black-footed ferret, our thought and all of our partners thought is that we can save the other 130 unique plants and animals that are native to the North American prairie.

And it's a pretty special ecosystem, one that's often overlooked because of the riches we have in our country.

JOHN YANG (voice-over): Another threat to the black-footed ferret, a bacterial disease called sylvatic plague both black-footed ferrets and the prairie dogs they eat are highly susceptible to it.

It's transmitted by fleas and has been known to infect humans.

Black-footed ferrets are nocturnal spending daylight hours in burrows dug by prairie dogs their lives there have largely been a mystery to scientists.

But this summer field biologist in Montana began the first ever tests of electronic devices to track prairie dogs under round into such a mess they're like Fitbits mapping their movement providing researchers with a wealth of data they hope will give them a better understanding of how the two species shared the networks of tunnels called towns.

HILA SHAMON, Smithsonian's National Zoo and Conservation Biology Institute: For the first time, we'll be able to map that and know how deep it is.

What are the densities of the animals?

What is the space that one black-footed ferrets is actually using out of that town?

Then what is the overlap between those ferrets, so we can know what would be a carrying capacity of a given prairie dog town.

JOHN YANG (voice-over): And cryogenic technologies allowing scientists to freeze black-footed ferret DNA in state of the art genome resource banks.

In 2020, researchers use the frozen cells of a black footed ferret that had been dead for 30 years to produce the first ever cloned member of the species, Elizabeth Anne.

JOHN YANG: So Adrienne, this is your breeding board.

ADRIENNE CROSIER: Yes.

JOHN YANG: Most of the mating comes naturally.

But some ferrets need a little encouragement.

ADRIENNE CROSIER: So we try to mix and match younger 90s males with older proven females and vice versa.

27.5.

JOHN YANG (voice-over): As a new generation of black footed ferrets weighs in the staff at the Smithsonian conservation biology center feels the weight of what's at stake.

PAUL MARINARI: So you go from the species that's thought to be extinct to all of a sudden, holy cow, we have the species we have to take care of them the fate of the species that is in our hands.

That's a huge responsibility.

People can make a difference.

And I think that is something that is important for people to hear JOHN YANG (voice-over): Exceptional measures to save a small but vital piece of our ecosystem.