Texas has a little bit of everything from the mouth of the Rio Grande to the Guadalupe Mountains in West Texas, and its biological flora and fauna are some of the most diverse in the nation.
But there is only one tortoise species in the state, the aptly named Texas tortoise, which is a state-listed threatened species native to South Texas.
And its challenges are many.
Some obstacles the slow-footed creatures endure are man made, like motorists speeding down highways and slamming into them.
Three years of extreme drought in South Texas also might be taking a toll.
“Everything’s going to suffer in the drought,” Gladys Porter Zoo Director Pat Burchfield said. “In turtle eggs, temperature determines sex. If extreme heat continues for a long period of time, the bias is going to produce female Texas tortoises.
“But there’s more than one factor killing Texas tortoises.”
Many of the creatures are also facing a fungal lung infection. Under most circumstances it is survivable. The drought might impose stress that makes it harder for them to endure the illness, but Burchfield just doesn’t know.
“It has been found in wild tortoises, but they seem to live with it unless they’re stressed, and extreme heat and drought could be a stressor,” he said.
However, by far the largest danger to Texas tortoises is humans speeding down highways.
“Road mortality is probably one of the biggest causes (of death). And one of the biggest contributors to that is probably the concrete barriers on the highway,” Burchfield said.
The barriers have periodic breaks — slots made at the bottom of the walls so that machinery can pick them up and move them — but they do not offer animals enough space to cross. Burchfield said barriers that use cables — like the ones around Raymondville — are more wildlife friendly.
“They (the tortoises) are more likely to get confused by the continuing inability to get across and get stuck in traffic and get killed,” he said.
The well-traveled highway leading to the popular getaway spot of South Padre Island — state Highway 48 — runs through the tortoise’s native land.
“Those are prime Texas tortoise habitats, and all the animals that are close to the road have probably been killed,” Burchfield said. “It takes years because of low reproductivity potential for animals to come back in and fill those areas.”
The tortoises don’t reach maturity until 15 or 20 years of age and can live to be older than 60. However, they only lay one to five eggs at a time, and those eggs are a delicacy for every predator in the South Texas brush, Burchfield said.
TAKING A TOLL
Not all of those traffic deaths are accidents.
“I’ve seen it. They (drivers) deliberately drive out of their way to run over it,” Burchfield said. “And I don’t know what kind of mentality is involved in that. But I’ve seen people, more than once, go out of their way into a parking lane to run over the Texas tortoise.”
Rolando Garza, chief of resource management at Palo Alto Battlefield National Historic Park, said while Palo Alto has a healthy population of roughly 160 tortoises, those that stray out of the park face deadly barriers.
“We have a healthy population, but because of all the development around here that is taking their habitat, we’ll be one of the islands and as the recession ends, we will eventually be a small green island in this area,” Garza said. “And two of our boundaries are lethal barriers — Paredes (Line Road) and (FM) 511. I have found dead tortoises that we marked (on the side of those roads).”
For instance, at Palo Alto, Garza said he and his team counted 40 different turtles during a two-day period in May, which is average.
Alternately, Sam Patten, a biologist with the Texas Parks and Wildlife Department, has seen the numbers of Texas tortoise in areas he is responsible for drop drastically.
Patten is responsible for counting the tortoise on two plots of the Las Palomas Wildlife Refuge, the Longoria and Arroyo Colorado units.
“Ten years ago on a normal day in either unit, I would tag and collect data on 20 or 30 tortoises that were everywhere,” he said. “It wasn’t unusual after a rainfall or sprinkle to see 25 drinking from a rain puddle at one time.”
But this year has been different.
He has found one live tortoise on each unit this year.
“I find the dead shells all the way through the unit and it’s not from predators because they have no predators — other than cars,” Patten said.
Suitable areas of habitat like Palo Alto Battlefield, Lulu Sams girls camp and large private ranches give the Texas tortoise habitats that are still lush and help the threatened species build mostly healthy populations.
“They’re probably not going to become extinct because of large tracts of private land that people can’t get onto that is far enough away from the highway,” Burchfield said.