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Environment

Scientists Are Trying To Save Texas Ocelots. So They Sent Testicles To Ohio

This young ocelot male was first detected by remote cameras at Laguna Atascosa National Wildlife Refuge in 2020.
Courtesy of U.S. Fish and Wildlife Service
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This young, male ocelot was first detected at Laguna Atascosa National Wildlife Refuge in 2020.

In late July, an ocelot had a rough day. He was killed by a car, and his testicles were sent to Cincinnati. Some of his sperm was sent to Albuquerque, and scientists will know if that effort paid off later this week.

Thomas deMaar, senior veterinarian at the Gladys Porter Zoo in Brownsville, received an unusual call in late July.

“Hilary Swarts called me during the night, I believe, to tell me that she had a report of a recently dead ocelot, that she was going to pick it up and she was going to put it on ice and bring it in first thing in the morning, and that we would try to collect the testes for the goal of collecting reproductive materials,” he recalled.

Swarts works for U.S. Fish and Wildlife Service, based at the Laguna Atascosa National Wildlife Refuge. She’s a wildlife biologist focused on ocelots.

hilary swarts.JPG
Dominic Anthony Walsh
Hilary Swarts stands next to a fence designed to guide animals towards a protected wildlife crossing under the road.

“We had a male — OM 283, lovely boy. He was about 9 years old,” she said. “Unfortunately, he was hit by a car on a road off of FM 106. He had been using those (protected wildlife road crossings) for nearly a year, safely, effectively. It was like, ‘This guy's got it.’ And then he went on a different route and unfortunately got hit by a car.”

It was a blow for the population of about 80 cats — the last remaining group in the United States, concentrated in patches of native thorn scrub habitats at the southern tip of Texas.

“They're really, really loyal to this one habitat type, and you don't really find them anywhere else,” she said. “Sometimes getting from one habitat patch to another requires crossing a road, and vehicle mortalities are the largest source of known mortality for ocelots.”

hilary swarts thorn scrub.JPG
Dominic Anthony Walsh
Swarts gestures over a field of non-native grass dotted with native thorn scrub plants in protective white tubes. Researchers hope this approach will reclaim ocelot-friendly habitat within less than two decades.

The small population size coupled with increasing habitat fragmentation has led to declining genetic diversity, an important factor for the health of any animal group. Scientists have tried to address the issue in a number of ways, from making it easier for the animals to move between habitat patches in Texas, to lobbying Mexican officials to import an ocelot from that country’s population.

“With an endangered species, you would like them to breed naturally,” explained Thomas deMaar. “You would like to put male and female together and create babies.”

Sometimes partners aren’t compatible, and they don’t always successfully reproduce before death.

“But we have found that if the gonads are collected soon after death, you can actually retrieve either sperm or eggs and then subject them to freezing, and they can be used at a later date to produce offspring in another uterus, so to speak,” he said.

That’s why he received the late-night call about the testicular removal.

Swarts and deMaar moved quickly. Artificial insemination is not a simple process. Even extracting the sperm from the testicles isn’t easy.

“Lovely boy” OM 283’s testicles were shipped overnight from South Texas up to Ohio, to Bill Swanson at the Cincinnati Zoo. He’s the director of conservation at the zoo’s Center for Conservation and Research of Endangered Wildlife.

“We received the sample here 36 hours after the cat was hit by the car,” he said. “That was extraordinary.”

Initially, he wasn’t too optimistic. The lab prefers to receive such genetic material within 24 hours of death. But he was surprised by the quality of the sperm. He credits the urgency and skill of Swarts and deMaar, although deMaar also points to “the power of the original male, may he rest in peace.”

“I collected the sperm. I got 250 million sperm, which was a lot,” Swanson explained. “I froze 20 semen straws, and theoretically, we could do 20 artificial insemination procedures with those straws. But in practice, that probably really means maybe 10 procedures because we want to maximize our chances to get a pregnancy.”

A large dose of the material has already been used at the Albuquerque Biopark in New Mexico.

“Her name is Lucy,” Swanson said. “She had eight ovulations on her ovaries which is a pretty large number for an ocelot, so that was very promising.”

He hopes the techniques used in this attempt — the first of its kind — could help researchers develop similar procedures for use outside of the zoo.

“That gives us a really direct way to address this population fragmentation and the limited genetic variation we're seeing in the wild ocelot population,” he said.

Swanson is from Texas, and he feels a special connection to the native species.

“Ocelots as a species are not going extinct anytime soon, but we may lose the population we have in the United States,” he said. “Once those ocelots are gone, we'll probably never have ocelots in the United States or Texas again, and I don't want to see that happen.”

Researchers will have a good idea of whether Lucy is pregnant later this week. Even if this attempt didn’t work, OM 283 gave them enough material for about nine other tries.