TPWD Print-Friendly Page:

Media Contact: TPWD News,, 512-389-8030 [TH]

TPWD Website:

TPWD News Release — May 23, 2005

Research To Document Agricultural Value of Bats

UVALDE, Texas — This month a team of scientists from Boston University, University of Tennessee, U.S. Department of Agriculture and Texas Parks and Wildlife Department will return to the Winter Garden agricultural production area near here for the second year of a five-year research project funded by a $2.4 million National Science Foundation grant.

The research seeks to better estimate numbers of Mexican free-tailed bats in Texas and to determine the dollar contribution of bats to protect corn, cotton and other crops against insect infestation. Early indications are that bats are worth millions of dollars in avoided pesticide use, which also benefits the natural environment.

The Mexican free-tailed bat (also known as the Brazilian free-tailed bat) is a 12-gram mammal that calls Texas home from March to October, when it migrates back to Mexico for the winter months. It is primarily females that migrate to Texas to take advantage of the massive numbers of insects, especially moths that lay eggs on local crops upon which the newly hatched larvae feed. Subsequent generations of adult moths migrate through Texas on their way to the Corn Belt of the Midwest.

While in Texas a female bat gives birth to a single pup. During this time, hungry mother bats can eat up to two-thirds of their body weight in insects each night. Scientists say that when you do the math for 100 million bats, the tonnage of insects consumed each night is staggering.

This spring and summer bat researchers will track the movement of moth caterpillars, especially the corn earworm moth, through a series of host plants that begins in Texas wildflowers and then proceeds to corn and cotton. Other scientists will determine what percentage of a bat's diet is made up of key agricultural pests. And, using infrared thermal imaging cameras, computer experts are creating software to count bats as they emerge from their cave roosts and forage over crop fields.

"Besides the opportunity to view spectacular bat emergences from Hill Country caves and bridges, this research shows Texans have even more to appreciate about bats," said Patricia Morton, who is coordinating bat media outreach and public education for TPWD. "For these very good reasons, the Mexican free-tailed just happens to be the official Texas State Flying Mammal."

Morton says the department will be producing bilingual educational products about the bat research project including a Video/DVD and children's book. For more information, contact Morton at or (512)912-7020.

The current research developed after the advent of National Weather Service radar in Central Texas in the early 1990s, when weather forecasters picked up mysterious large "clouds" in areas where no storm activity was expected. The clouds turned out to be millions of bats emerging from cave roosts.

Soon after this discovery, another National Weather Service radar service became operational in southern Texas and detected additional strange clouds that were intersected by the bats at altitudes of thousands of feet. These were found to be clouds of millions of migrating moths-a favorite food of free-tailed bats.

A few years later, following a variety of studies incorporating bat detection devices riding on weather balloons, insect identification from bat guano and the development of genetic markers for moth species, scientists were able to document that the Mexican free-tailed bats were feeding on some of the state's most damaging agricultural pests, those which feed largely on cotton and corn.

Meanwhile, growing tourism to see dusk emergences of large bat colonies continues to spread. All told each year in Texas, tens of thousands of people witness clouds of bats spiraling out of caves at places like Devil's Sinkhole State Natural Area near Rocksprings, Old Tunnel Wildlife Management Area near Fredericksburg, Bracken Cave north of San Antonio, and the Congress Avenue Bridge in Austin, home to the world's largest urban bat colony.

More information about bats and where to see them in Texas is on the Bat Conservation International Web site.


On the Net: