Round Rock Edition | March 2026

Round Rock bat colony to emerge for spring From the cover

The big picture

Nightly flights From March to September, around sunset the bats fly toward agricultural areas, such as Hutto and Taylor, to feed on pests, such as moths, beetles, flies and other insects.

Annual migration Austin Bat Refuge co-founder Lee Mackenzie said some bats choose to remain in the roost over the winter. Some bats do leave for warmer temperatures around October and November, according to Texas Parks & Wildlife.

Bats have a strong presence in Central Texas, proving a challenge to both local road crews and the Texas Department of Transportation. However, a future project to widen I-35 in Round Rock could see an increase to available habitat. As the wintry nights of February warm to springtime in March, area residents may be familiar with the sight of small, fast and chirping nocturnal mammals ying around town at sunset during the spring and summer. Lee Mackenzie, who co-founded Austin Bat Refuge with Dianne Odegard, said the species of bats residing under the bridge are the fastest animal capable of true ight. The nonprot rescues and rehabilitates injured or orphaned bats in Central Texas. Mackenzie said that during winter weather events, such as the recent Winter Storm Fern in late January, his organization checks nine bridges for bats that have fallen as a result of being cold-stunned. Two of these bridges are in Round Rock: the intersection of I-35 over McNeil Road and the

Taylor

130 TOLL

Hutto

Texas

Round Rock

ROUND ROCK

U.S.-MEXICO BORDER

Mexico

SAN MATÍAS

SOURCE: AUSTIN BAT REFUGECOMMUNITY IMPACT

“We don’t know exactly what happened to the ones at McNeil,” Mackenzie said. “We just know that they didn’t show up on radar in the following month.” As of February, he said the populations observed on Doppler radar have returned to the 300,000 bats seen spending the winter in Round Rock. State agencies and nonprots are mainly responsible for bats’ welfare, including those in Round Rock.

South Mays Street Immortal Ten Bridge over the Union Pacic Railroad line. In recent years, Mackenzie said bat populations observed by his organization have rebounded from the 2021 Winter Storm Uri, during which he estimates about 500,000 bats in Central Texas succumbed to weather-related deaths, or left. His organization revived approximately 1,200-4,000 bats in the area at that time.

Bat boxes

Managing the impact

What the experts say

A single bat box can serve thousands of bats. Bat boxes used by TxDOT measure approximately 4 feet high, 2 feet wide and 4 feet long. Bat boxes were first used by TxDOT in a Waco bridge project. Large bat boxes cost TxDOT $3,000-$4,000.

Mexican free-tailed bats are one of 10-12 species residing in Central Texas, with a total of 32 species across in the state, according to Texas Parks & Wildlife. Tracy White, an environmental specialist with TxDOT, said the state’s availability of caves and crevices made the area appealing to a variety of bat species. As Central Texas was developed, man- made habitat and local culture of appreciation for bats have allowed them to flourish. Several bridges in the area are built with a box- beam structure, she said, creating small spaces that bats find appealing. “I know if there’s a crack, they’ll be there,” White said. As part of the I-35 Capital Express North project, TxDOT installed 36 bat boxes, or artificial habitats, under bridges known to be home to bats, White said. Mackenzie said active construction in the area also provides ample human-made habitat for Mexican free-tailed bats in particular, as they are known to be “crevice bats.” “When the cold weather comes, oftentimes they will look for places to shelter from the freezing cold temperatures and they’ll go into buildings,” he said. When the colony at the McNeil bridge emerges

White said that as TxDOT planned its I-35 expansion, bats were a central consideration in setting new intersections. Several road intersections on the highway are home to relatively small numbers of bats, she said. Crews carefully removed bats from the habitat before construction began, she said, to prevent harm to bats. While bat boxes are a suitable solution for other populations, White said the McNeil Road colony is too large for the boxes to accommodate, and the bridge itself must serve as a habitat. Plans for a new bridge at the intersection are early, but it will use the same box-beam style that can house bats.

SOURCE: TXDOT/COMMUNITY IMPACT

for the evening, Mackenzie said the bats fly eastward toward Hutto and Taylor to feed on bugs in agricultural areas. If bats had not recovered from the impact of Uri, he said, farmers in the area would be some of the first to know. “The farmers would know the difference because they wouldn’t have free pest control to the tune of billions of dollars annually,” he said. According to a report from Bat Conservation International, a 2011 study estimated that Mexican free-tailed bats provide pest control services valued at about $23 billion annually in the U.S.

How it compares Central Texas is home to many bat colonies. Here’s how the McNeil colony compares:

Bracken Cave Preserve 15M bats

South Congress bridge 1.5M bats

McNeil bridge 500K+ bats

SOURCE: BAT CONSERVATION INTERNATIONAL/COMMUNITY IMPACT

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