WOODVILLE, Texas — With narrow lanes and soft, weedy shoulders dropping steeply to the water, U.S. 190's Steinhagen Lake crossing is bound to send an adrenaline jolt through all but the most blase motorists.

The roadside shards of exploded tires speak of danger as eloquently as a skull beside a desert waterhole.

But the very conditions that make a driver snap to attention and ease up on the gas are a magnet for fresh-water turtles who, oblivious to the danger, die beneath the wheels of thousands of cars and trucks that pound across the causeway each day.

So great has been the mortality of female turtles, who are drawn to the causeway to lay eggs, said Houston Zoo Conservation Programs Manager Rachel Rommel, that the future of the lake's turtle population may be in jeopardy. A drop in the Steinhagen's turtle population, she said, might pose serious threats to the lake's overall health.

Monthly surveys taken during the turtles' spring and summer nesting season indicate the two-mile stretch of road is among the top five deadliest spots for turtles in North America. Since the summer of 2008, zoo workers under Rommel's direction have found the remains of 635 turtles.

Rommel conceded that the condition of the Steinhagen's turtle population is unknown but said natural predation, the large-scale harvesting of freshwater turtles for export to China a practice banned in Texas public waters in 2007 — and the reptile's slow sexual maturation make the roadway losses a matter of significant concern.

Based on the survey, zoo officials have petitioned the Texas Department of Transportation to erect low fences, or take other actions, to keep the turtles from crossing the road.

Transportation agency biologist Stirling Robertson said TxDOT officials, aided by state and federal wildlife experts, are reviewing the issue. "We don't have a lot of experience in dealing with this kind of problem," he said, while noting that his agency has elsewhere installed fences and culverts to protect the endangered Houston toad.

Rommel said a fence and culvert program in Lake Jackson, Fla., the continent's deadliest turtle road kill spot, reduced mortality from about 10 turtles per kilometer per day to less than one.

Birth of surveys Rommel, 32, became aware of the Steinhagen Lake turtle deaths in spring 2008 while camping at Martin Dies Jr. State Park at the causeway's eastern end.

En route to a nearby grocery, she spotted an injured turtle near the road. "She was still alive. I patched her back together," Rommel said. Now on the alert, she counted 35 dead reptiles on or near the roadway as she returned to her camp.

Rommel's reports on turtle carnage launched the zoo's annual surveys.

Almost all the dead turtles, she said, are female — apparently drawn to the causeway to lay eggs.

The soft, sandy soil retains heat and is close to aquatic plants, which may make the road's shoulders an appealing spot to nest, Rommel said.

Dead turtles almost always are red-eared sliders or Missouri River cooters, which can grow to near dinner-plate size and live for decades. Rommel said females of these species can lay as many as 20 leathery eggs up to three times per nesting season, usually late spring through August.

The zoo team surveys the Steinhagen Lake site once monthly through October.

As vehicles sped past at seemingly breathtaking speeds, Rommel and three colleagues last week scoured both sides of U.S. 190 in search of dead turtles.

With each find, they recorded species and sex and noted its location with a global positioning system. When only shell fragments were found, they labeled the find an "unknown." After logging the data, the reptiles were tossed into the lake.

The August survey found 98 dead turtles as well as snakes, raccoons and an alligator.

"It's a sad thing," Rommel said. "After disposing of turtle after turtle, you have to shut off your emotional response and get the job done."

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Whether eating or eaten, turtles are a key element in the lake's ecosystem, the health of which is vital to the area's water-based recreation industry, Rommel said. And even though neither red-eared sliders nor Missouri River cooters are protected species, a skewed ratio of males to females could mean trouble in years to come. "Because they have such a long life," she said, "you can see a bunch of old males sitting on a log and say, 'OK, everything's fine,' when it may not be."

TxDOT's Robertson hinted that the effort to save turtles might draw opposition from Texans who think highway dollars should target more traditional projects. And, he noted, while turtle fences or culverts might be cheap to put up, the state would then have to maintain them.

Still, he said, keeping turtles from crossing U.S. 190 might be warranted in terms of highway safety.

"If a shell punctures a tire, a motorist could get in big trouble," Robertson said. "It's a very narrow elevated roadway, and you don't have a lot of options. You go into a tree or into the lake."

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