JOHN YANG: Finally tonight, while ocelots are widespread in south and Central America, in the United States they're on the brink of extinction.

They were once over hunted for their coats and now they face shrinking habitats.

Researchers hope that the key to restoring this species can be found in fertility treatments.

This is part of our series Saving Species.

JOHN YANG (voice-over): In an operating room in Texas, veterinarians prep their patient for surgery.

Mila is a five-year-old ocelot, a wild cat similar to A leopard or jaguar distinguished by their spotted golden brown fur.

BILL SWANSON, Director, Animal Research: They're among the most beautiful cats in the world as far as different species go.

JOHN YANG (voice-over): Ocelots were once plentiful in the U.S. Southwest, but now fewer than 100 remain in Arizona and Texas as human activity has eaten away at their habitat.

Since 2023, a team from the Cincinnati Zoo has been part of efforts seeking to boost their numbers by attempting to breed wild ocelots with those in using fertility treatments.

Bill Swanson is the zoo's director of animal research.

BILL SWANSON: Just look at the cat.

I mean, why would you not want that animal to survive in nature?

JOHN YANG (voice-over): The collaborators on this project are four zoos, Texas A and M University, and the East Foundation, a southwest Texas nonprofit that protects wildlife habitats through land conservation practices.

In the operating room, Mila's eggs are surgically removed, fertilized with a male's semen, and placed in an incubator.

BILL SWANSON: That's part of the process that we have to build up the managed population in the breeding facility that we can rewild and put back in nature.

JOHN YANG (voice-over): Ashley Reeves is a research veterinarian at the East Foundation.

ASHLEY REEVES, Research Veterinarian: When the fur trade became very popular, they were hunted down for their beautiful fur and then also loss of habitat, human encroachment, large cities being built, and roadways.

JOHN YANG (voice-over): Unlike domestic cats, ocelots typically produce very small litters.

BILL SWANSON: An ocelot usually has one kitten.

So ocelots are very slowly reproducing animals naturally in a lab.

JOHN YANG (voice-over): Reeves checks on Mila's procedure.

In recent years, her team has attempted 13 artificial inseminations and four in vitro fertilizations.

None were viable.

ASHLEY REEVES: So we're seeing an egg from her procedure, and were hopeful that it was fertilized and cleaved, but it did not.

And so it's just an egg that did not fertilize.

So we do not have it in for you.

JOHN YANG (voice-over): Still, Reeves and Swanson say each attempt brings them closer to rebuilding the ocelot population.

BILL SWANSON: It's not just saving the ocelot.

It's saving the habitat and ecosystem where it lives.

JOHN YANG (voice-over): By this fall, there will be a new facility in South Texas where ocelots will undergo fertility procedures and where these endangered cats can learn how to thrive in the wild.