Bat habitat support taking off statewide
July 18, 2024
By Paul Stinson
AUSTIN — As TxDOT Travel Information Centers statewide gear up to host the tourists of summer’s peak-travel season, the agency is also extending its hospitality by completing Austin’s largest-ever accommodation for its most famous visitors: bats.
This summer, TxDOT will install an additional 18 artificial roosts or “bat boxes” at the Walnut Creek Bridge along I-35 to offset the impact of construction on a pair of bridges that once offered cozy crevices to the Brazilian free-tailed bat— one of the 32 bat species found in Texas.
“We wanted to give the bats alternate roosting habitat so that when we excluded them from the habitat under the Wells Branch Parkway and Howard Lane bridges, they would have somewhere else to go,” said TxDOT Environmental Specialist Tracy White.
The installation of a combined 36 boxes is part of the I-35 Capital Express North project, a $606 million project to improve traffic flow in Austin as part of TxDOT’s Texas Clear Lanes initiative to offer relief to the state’s most congested roadways.
White said it can take some time for the bats to find their new accommodations, adding that site selection is typically governed by distance from humans and proximity to constant water sources to ensure easy access to food including a nightly bug buffet that includes pesky mosquitoes.
Bat roosts catching on statewide
With future bat boxes already part of projects planned for this decade and the next, usage and popularity of the roosts is expanding from its Central Texas roots into several corners of Texas —Shelby County in the east, Fort Worth, Lubbock and Amarillo in the north, and Corpus Christi to the south.
The bat box made its debut 2019 along I-35 in Waco and was the result of a brainstorm between multiple TxDOT districts and design staff ialong with Bat Conservation International.
Construction of large bat boxes typically run in the $3,000 to $4,000 range and measure 4’ by 4’ by 2’ — each capable of providing roosting and maternity colony opportunities for thousands of bats.
The latest Austin installations will support the Brazilian free-tailed bats, which live up to 11 years in the wild and use their seasonal residency in Texas to birth and nurture their young pups.
Also known as Mexican free-tailed bats, the official Flying Mammal of Texas soars at speeds up to 99 miles per hour. Mother bats give birth to single pups in June or July followed by long-distance flights in search of enough food, consuming approximately her own body weight in insects.
Bat origins story
TxDOT’s bat connection traces its roots to the 1980 rehabilitation of Austin’s Congress Avenue Bridge — an effort which included the installation of box beams which created the crevices that bats love.
Word got out quickly in the bug-eating and flying mammal community. It wasn’t long before the bridge became host to the world’s largest urban bat colony. TxDOT’s support of bat research began in the 1990s, a decade that included the Laredo installation of a “bat dome” over a culvert to offer crevices to a segment of the local population.
Bats under threat
The need for bat-supporting habitats is increasingly critical following Texas’s first confirmed case in 2020 of White Nose Syndrome, a deadly fungal disease that has wiped-out millions of bats in North America since 2006.
“TxDOT bat stewardship efforts are highly important and have only gained in importance with the spread of WNS through the northeast United States,” TxDOT Environmental Planners John Young Jr. and Lauren Young said in a joint interview.
Although there are no reported mass die-offs from WNS in Texas, cave bat populations in the Panhandle and Central Texas are projected to experience a 75% and up to 50% reduction respectively over the next ten years, according to predictive models.
Future projects
Meanwhile, up in the Panhandle, Environmental Planner Max Graff said the Amarillo area will build off the success of boxes already in place along the U.S. 60/83 Canadian River Bridge. Between three to six new roosts will be a part of a McClellan Creek bridge project that will go out to let in 2027, according to Graff.
Future Austin projects include 24 boxes along the underside of the I-35 pedestrian bridge over Lady Bird Lake sometime in the 2030s for the Capital Express Central project and six on the I-35 northbound frontage road over Onion Creek for the Capital Express South.
Even in parts of Texas where roosts have yet to take flight, enthusiasm abounds.
“We do not currently have any bat boxes on our bridges, but I am very interested in implementing them on our projects in the future,” said Holly Brady, an Environmental Project Planner stationed in TxDOT’s Odessa area.
Meanwhile back in Corpus Christi, Amy said that looking for ways to support Texas bats is now standard procedure.
“What we’re doing from a planning level perspective is that as bridge projects come up where we identify them as being a good candidate for a bat box, we’re going to include them now,” said TxDOT Environmental Coordinator Kimberly Amy. “That’s now just part of the way we develop projects.”
Additional reporting by Antonio Lujan