In the race to save the endangered ocelot, scientists are trekking the United States, pursuing fertility treatments and striving to kickstart a new generation of the wild cat.
Ocelots roamed the southwestern US in the 1800s, but have since dwindled to fewer than 100 in two small breeding populations in South Texas.
While the feline species is found in Mexico, Central America and South America, the Texas cats with striking spotted coats are believed to be the last wild population in the United States.
"Just look at the cat – why would you not want that animal to survive in nature?" said Bill Swanson, the Cincinnati Zoo's director of animal research, who has traveled the country trying to breed captive ocelots in animal institutions with sperm from wild ocelots from South Texas ranch land.
"It's not just saving the ocelot, it's saving the habitat and the ecosystem where it lives, which supports so many other animals that provide those services that let people survive on this planet," he said,
The nonprofit East Foundation, based in San Antonio, manages one of those breeding populations on more than 200,000 acres (810 sq km) of South Texas ranch land containing thorn scrub habitat, a dense covering of short, spiky shrubs that the elusive and nocturnal ocelots adore.
Ashley Reeves, a research veterinarian at the East Foundation, said humans played a major role in the decline of the ocelot, listed in 1982 as an endangered species in the US.
"Back when the fur trade became very popular, they were hunted down for their beautiful fur," Reeves said. "And then also loss of habitat, human encroachment, large cities being built and roadways, so roadways are one of their No. 1 killers today."
Reeves and Swanson have been working on their ocelot project since 2021. The team has tried - unsuccessfully so far - to breed ocelots two ways.
The first is via artificial insemination, in which semen collected from a cat is deposited directly into a female cat's reproductive tract.
The second is in vitro fertilization, in which oocytes, or eggs, are collected from the female cat's body and fertilized with semen in a petri dish before developing into an embryo in an incubator. The viable embryo is then surgically transferred into a cat or frozen to be transferred later.
Of the 13 artificial inseminations and four in vitro fertilization procedures performed in recent years, none have produced a viable pregnancy.
Swanson points to decreased quality in wild ocelot sperm due to signs of inbreeding, environmental stresses like dehydration from drought and decreased motility - the ability of sperm to move - from freezing specimens.
"An ocelot usually has one kitten. That's the normal litter size," Swanson said. "And in the wild, the mother will raise that kitten for a full year until it's old enough to go out on its own. So ocelots are very slowly reproducing animals naturally."
At the Texas State Aquarium in Corpus Christi, Texas, in December, the team extracted two eggs from a five-year-old ocelot named Milla and patiently waited to see if an embryo would form after combining the eggs with wild sperm in a petri dish. After two days of waiting for a fertilized egg to cleave, or rapidly divide and develop into an embryo, the researchers were disappointed to find neither cell cleaved.
"It's disappointing," Reeves said. "But at the same time, science doesn't always go the way you expect it to."
Researchers will spend the next few months trapping wild male ocelots to collect their sperm before resuming fertility procedures in the fall.
By the end of the year, a facility in Kingsville, Texas, will be constructed to house ocelots, provide medical and reproductive care as well as a setting for young ocelots to learn how to hunt in the wild.
