Houston Bats Rescued and Released After Cold Sent Them Into Shock

Bats can sleep upside down, fly at up to 100 miles per hour and use their own version of sonar to hunt down insect hunters. But they can’t stand cold weather.

The powerful winter storm that swept across much of the United States last week proved nearly too strong for hundreds of the flying mammals that make their home in Texas.

As freezing temperatures took over the state before the holiday weekend, colonies of bats, which have little body fat to keep them warm, went into hypothermic shock across the Houston area, animal advocates said.

Temperatures in Houston dropped from 58 degrees on Dec. 22 to 15 degrees the next day, according to the National Weather Service. The cold was too much for hundreds of Mexican free-tailed bats hanging out under the Waugh Drive Bridge in Houston, and they fell 15 to 30 feet onto the pavement below, according to the Houston Humane Society. Over a few days, they were rescued by the nonprofit, along with more than 900 other bats in Pearland, Texas, a suburb of Houston.

In total, 1,544 bats were rescued in the Houston area. More than 50 bats from Pearland were in critical condition when they were rescued, requiring intensive care in an incubator, according to the humane society. Many of the other bats needed only heat and fluids to recover.

“Amazingly, most of bats have survived,” the Houston Humane Society said in an update on Dec. 24.

Mary Warwick, a director at the Houston Humane Society’s Texas Wildlife Rehabilitation Coalition, kept hundreds of the bats in dog kennels in her home’s attic.

In an update on Dec. 26, Ms. Warwick shared a video of hundreds of the bats huddled together inside the kennels. Ms. Warwick said that their recovery was focused on keeping them hydrated and on moderating their body temperature.

“They can do without food,” Ms. Warwick said as the bats squeaked in the background. “It’s hard to feed bats in care because they normally eat in flight, so we could have to force-feed 1,544 bats, which is a lot.”

By Wednesday afternoon, temperatures in the Houston area had rebounded into the 70s, and many of the bats were healthy enough to be released back into their colonies. Dozens of people went out to the Waugh Drive Bridge to see 693 of them released. Many of the bats took to the sky while a few struggled to fly, according to the Houston Humane Society.

Hundreds of other bats were released in Pearland later on Wednesday night, the nonprofit said in an update, explaining that the bats had been “minutes away from freezing to death last week.”

Ms. Warwick returned to Waugh Drive Bridge on Thursday morning to see if there were any bats on the ground. She said she found none, indicating they were healthy enough to be released.

“I think in general the operation was a success,” Ms. Warwick said in an update on Thursday.

Five of the 693 bats released at the Waugh Drive Bridge on Wednesday did not fly, and they were taken back for further treatment before another attempt to release them on Thursday afternoon, Ms. Warwick said.

Texas is home to 32 of the 47 species of bats found in the United States, according to the Texas Parks and Wildlife Department.

Of bats found in Texas, Mexican free-tailed bats are among the most common. They spend the winter inside caves in Mexico and then migrate to Texas in February, according to the department. The bats are drawn to Texas because of its warm and humid weather, but they return to Mexico when temperatures drop in the winter, the department said.

Large bat colonies have been a staple tourist attraction in some cities across Texas for several years. Every year, about 140,000 people visit the Ann W. Richards Congress Avenue Bridge in Austin to see one of the largest urban bat colonies in the world, with an estimated 1.5 million bats, according to the parks and wildlife department.

In cities across Texas, bats emerge from under bridges around sunset, dotting the sky as they set out in search of mosquitoes and other insects.