The Texas Department of Transportation’s ongoing expansion of the Interstate 35 highway is displacing several bat colonies nested in the crevices of the highway’s bridges. 

TxDOT is set to demolish and rebuild multiple bridges as a part of its Capital Express North, Capital Express Central and Capital Express South projects. The northbound I-35 bridge over Wells Branch Parkway was demolished in September, and the northbound bridge over Howard Lane was demolished in late October, said Tracy White, an environmental specialist within TxDOT’s Austin district. White estimates about 15,000 to 20,000 bats dwelled in the Howard Lane bridge and 10,000 to 15,000 dwelled in the Wells Branch Parkway bridge. 

White said these bridges are box beam bridges, meaning they have crevices and thermal properties that provide the ideal space for bats to perch.   

Prior to demolishing the bridges, TxDOT gradually relocated the bats through a process of exclusion. One of the methods the department uses is spray foam, a permanent form of exclusion, which is used to seal up the gaps in the bridges. Another method of exclusion is jamming pool noodles through the cracks of the bridges. 

“This is the first exclusion TxDOT has done on this big of a scale,” White said. “We’re setting a precedent for the rest of the state. I’m glad I’m able to talk to the construction people because then I can spread my concerns (and) take care of these bats.” 

Fran Hutchins, a director of Bat Conservation International, an organization dedicated to the mammal’s conservation, said TxDOT is relocating the bats during times when they naturally migrate and forage for food. When the bats come back, they are forced to move somewhere else, he said. 

“They’re basically doing the best that they can and with the resources they have,” Hutchins said. “They are generally concerned about the state mammals.”

White said TxDOT also built bat boxes near Walnut Creek in March and throughout the summer before demolishing the bridges to provide an alternate habitat for the bats, and the hope is that when the bats migrate, they will find the bat boxes. 

“I’ve been worried a lot,” White said. “The concern that I have had has just been making sure we do as little harm to these bat colonies as possible, and if possible, build back a larger structure for more habitat.”