Last Updated August 2025
Bats
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Bats. Los murciélagos. Die Fledermäuse. Flying mice. Blood-sucking vampires. Stuck in your hair. Little flying rabies delivery devices. Scary creatures of the night. Bats are one of our more common yet misunderstood local animals. They are an important part of our local ecosystem, eating insects that bother or harm people (like mosquitos) or that damage crops (like the corn earworm moth), pollinating night blooming plants (including some agaves), spreading seeds from fruit, and adding nutrients to soil through their guano. Bats are a symbol of Austin, and bring bring an estimated $10 million a year in tourist-related revenue to the capital city.
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The Eastern Red Bat (Lasiurus borealis) featured on the Bats Honor
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About Bats
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Bat Anatomy
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Bats are mammals, the only mammal that can actually fly (flying squirrels and flying lemurs merely glide). Like other mammals, bats are warmblooded tetrapods (they have 4 limbs), they have fur or hair, give birth to live young, and suckle those young. Despite the phrase “blind as a bat,” most bats have good eyesight. The night-flying bats have eyes adapted for low-light conditions, while day-flying bats have eyes adapted to dusk and dawn foraging.
Bats are in the order Chiroptera, a word taken from Greek meaning “hand-winged.” The clawed bat thumb sits along the leading edge of the wing, and in many species serves as a tool to assist in climbing. The remaining four fingers support the membrane of the wing, thus living up to the name Chiroptera. 
The order Chiroptera is divided into two suborders, Yangochiroptera (those that use true echolocation) and Yinpterochiroptera (those that do not use echolocation, and instead primarily rely on eyesight). An alternate division for bats is Vespertilioniformes (similar to the Yangochiroptera) and Pteropodiformes (similar to Yinpterochiroptera). Scientists and taxonomists have not fully agreed as to which should be the name for the suborders of bats. Traditionally, bats were divided into two groups, the Microchiroptera or micro-bats (mostly hunting or pollinating bats) and Megachiroptera or mega-bats (flying foxes and other fruit and flower-eating bats).
The primary problem with using the mega- and micro- classification is first, that there are many small “mega” bats and several large “micro” bats. Several species of flying foxes have a wingspan reaching 5 feet or more, one of the largest being the Giant Golden Crowned Flying Fox (Acerodon jubatus). But another traditional “mega” bat, the flower-feeding Dagger-toothed Long-nosed Fruit Bat (Macroglosus minimus), has a wingspan of less than 7 inches. On the “micro” bat side of things, the smallest is likely the Bumblebee Bat or Kitti’s Hog-nosed Bat (Craseonycteris thonglongyai), with a wingspan of just 6 inches, the largest of the “micro” bats being the Spectral Bat (Vampyrum spectrum), a South and Central American species that preys on birds, bats, and rodents.
Further, genetic information now suggests closer relation between some traditional mega and micro bats and less close relation among some micro-bats than previously thought. Thus, most “micro” bats are now placed in Yangochiroptera/Vespertilioniformes and the “mega” bats, plus a few of the old “micro” bats, are placed in Yinpterochiroptera/Pteropodiformes. Bat Predators
Here in Central Texas, many animals eat our native bats. In the evening, snakes including Coachwhips may hang out by cave entrances, waiting to snag an evening snack. Owls hunt bats, Bobcats and Raccoons may eat bats they find on the ground (remember, bats must fall to fly, so if they land on the ground, they cannot fly away until they climb a tree or other object first). In the morning, as bats return to their roost, Hawks and Falcons may fly through the swarms of bats, snagging them out of the air for a mid-flight snack. The video above shows a colony of Mexican Free-Tailed Bats being preyed upon by Swainson's Hawks.
Other Challenges for Bats
One of the most significant challenges for bats is loss of roosting areas and disturbances by man. In our hibernating bats, there is a risk of contracting White Nose Syndrome, a fungal infection that has decimated some bat colonies as it spreads across the United States. White Nose Syndrome began showing up in the early 2000s in the Northeastern United States, perhaps brought in from Europe (where it doesn’t seem to affect bats). North American bats may not have had any immunity to this fungus, and in some places there were 90 percent population declines as the disease devastated colonies. There are signs, however, that some bat colonies are slowly rebuilding, suggesting perhaps the emergence of immunity (though this is still being studied). Nonetheless, it may well take several decades for a bat colony to regain its former strength, given their frequently slow birthrates. Among the many challenges bats face (habitat loss, pesticide use, etc), they also seem to be more susceptible to strikes on wind power towers than are birds. It is not entirely clear why the bats are attracted to the towers. Tree-dwelling species may consider them ideal tall roosts. Bats may be attracted to the sound of the blades, or they may use the towers as places to communicate through pheromones. It may be several different reasons. Researchers are testing different bat deterrents, working with the wind generator manufacturers and operators. These include curtailment (stopping blades during peak bat activity), or direct deterrents like ultrasonic sound generators. However, current sound generators need power, and are thus located on the nacelle, but as blades grow longer, the sound waves do not travel as far as the blade tips. New passive devices are being explored that could be added to the blades without interfering with operations. Bats and Rabies
Bats, like most mammals, can carry rabies. Although studies show that less than 1% of bats are likely to contract rabies, bats are one of the more common transmitters of rabies to humans in the United States. Healthy bats generally stay away from people, but rabid bats may behave erratically, or be found on the ground, leading to greater interaction with people, and a higher chance of a bite. Bats found on the ground should not be picked up - call a wildlife rescue service if you think you have found a stranded or injured bat. 
The Guano mineshaft at Bracken Cave.
The Benefits of Bat Poo
Guano, another name for bat poop, is rich in nitrogen, phosphorus, and potassium - all nutrients needed for good plant growth. Bat guano is used in fertilizer even today. Bat guano was also once a source of Salt Peter (Potassium Nitrate - KNO3) used to make gunpowder, with both Longhorn Caverns and bracken Cave once sources of Salt Peter for teh Confederacy during the Civil War. Mining bat guano can be dangerous - large piles can form breeding grounds for Histoplasma capsulatum, a fungus that, when disturbed, may release spores that can be inhaled, causing histoplasmosis, which may damage the lungs. |
Central Texas Bats
All of our central Texas bats fall within the Yangochiroptera/Vespertilioniformes/Microchiroptera suborder. We have at least 9 species of bats locally, of the total more than 30 species found in Texas (a small fraction of the estimated 1400 species worldwide). These include our Austin favorite, the Mexican (or Brazilian) Free-tailed Bat (Tadarida brasiliensis) that lives under the Congress Avenue Bridge, and our common cave-dwelling Tri-colored Bat (Perimyotis subflavus), found in several of our local show caves.
The Mexican Free-Tail Bats are communal roosters, living together in large groups in cracks and caves. The Tri-colored Bat usually roost alone, though females may form small maternity roosts, living together as they raise their young. Unlike most bats, which bear just one “pup,” Tri-colored bats often have twins, each weighing just 1.6 grams (or less than four thousandths of a pound). Tri-colored Bats are one of the species that exhibit delayed implantation - after mating, the female retains the male’s sperm during the hibernation, only allowing it to fertilize the egg in the spring. Tri-colored Bats hibernate in the winter, but out Mexican Free-tail bats migrate, leaving Austin for warmer climes in Mexico. Many ofd the “mega” bats in tropical countries are active year round, but few of our bats here in Texas choose to neither migrate nor hibernate. Mexican (Brazilian) Free-Tailed Bat (Tadarida brasiliensis)
Additional Information: BCI, TPWD, ABR, ADW Southern Yellow Bat (Dasypterus ega)
Additional Information: BCI, TPWD, ABR, ADW Hoary Bat (Lasiurus cinereus) Additional Information: BCI, TPWD, ABR, ADW Seminole Bat (Lasiurus seminolus) Additional Information: BCI, TPWD, ABR, ADW Evening Bat (Nycticeius humeralis) Additional Information: BCI, TPWD, ABR, ADW Cave Myotis (Myotis velifer) Additional Information: BCI, TPWD, ABR, ADW Bats in the Bible
Bats are only mentioned three times in the Bible, and some scholars do not agree that all three are translated correctly. In Leviticus 11:19 and Deuteronomy 14:18, bats are mentioned among the birds the Israelites are forbidden to eat. As we have seen, bats are not birds, so there is some question as to whether this is the correct translation, or whether there was not a clear an understanding of taxonomy. In Isaiah 2:20, we see bats and moles mentioned as two animals that live in the clefts and crags of rocks. |
Some interesting information about Austin's Mexican Free-tailed Bats and their roost under the Congress Avenue Bridge
- The 1980s remodeling of the Congress Avenue Bridge included the new expansion joints, which proved exactly the size and shape that Mexican Free-Tailed Bats need for roosts.
- The crevices in the bridge also stay warm overnight due to the heating of the concrete and bridge deck, making it a perfect nursery for baby bats that need to stay warm.
- Initially, many Austinites were upset by the rise in bats, due to misinformation and poor knowledge of the benefits versus risks of bats.
- Merlin Tuttle was instrumental in shifting attitudes in Austin, focusing on education of students (who then shared information with their parents), changing the general perception of bats from a dangerous nuisance to an integral part of “weird” Austin.
- Bats now bring some $10 million a year in revenue to Austin, primarily from tourists coming to see the bats.
- The colony in the Congress Avenue Bridge is a nursery colony.
- Mexican Free-Tailed Bats only have one pup a year. The mother spends the first 2-3 days with their pup after birth, allowing both to learn one another’s smell and sound. The mother bats find their own pups when they return to the roost - they do not just feed any pup as was once thought.
- When feeding, Mexican Free-Tailed Bats can fly out 60-100 miles from the bridge at night, and fly up to 10,000 feet (where they hunt the high-flying Corn Earworm Moth). The bats can reach speeds of 100 miles per hour during their flight, and eat as many as 1000 insects an hour.
- The Mexican Free-Tailed Bat has been recorded at 108 MPH in level flight in one study - a speed that would not only make it the fastest bat on the planet, but the fastest flying animal in level flight. (See the original research report, a note from Guinness World Records, a report from Bat Conservation International, and an article in New Scientist.
- Mexican Free-Tail Bats appear to communicate through at least 30 identified different types of calls, as well as through pheromones. Baby bats “babble” with repeated “syllables,” similar to human babies, to get attention from their mothers.
- In is unclear exactly where the Congress Avenue Bridge bats migrate to in the winter, but they may spread over many different caves and crevices across Mexico.
- Not all the Congress Avenue Bridge bats migrate - some 150,000 may stay year round, while the remainder of the 1.5 million head south for the winter.
- Because the Mexican Free-Tailed Bats are so light, it is nearly impossible to mount any tracking device on them that could contain a battery to power a GPS, adding to the difficulty of tracking and learning more about their migration and flight patterns. Trackers mounted on the animal generally shouldn’t be more than 3-5% of the animal’s body weight.
- The Congress Avenue Bridge bats seem to leave the roost earlier in the evening when they are hungrier (for example during extended periods of drought or limited rain), and later in the evening during wet times when they may have plenty to eat.
- Some bats leave earlier than the bulk. These “scouts” may just be hungrier, but they flit around the bridge, calling the others out. Bats are safer en masse when they emerge, as predators may be waiting.
- In our area, some of the predators of bats include coachwhip snakes, hawks, falcons, owls, raccoons, skunks, and pretty much anything that can eat them.
- Bats cannot get lift on their own - they need to fall to fly. If a bat ends up on the ground, it cannot take off, it needs to climb back up something to leap off.
All images and text by R. Baker unless otherwise noted.
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Bat Honor Requirements
1. Why are bats classified as mammals and not birds? 2. What is the main characteristic that separates bats from all other mammals? 3. What is the name of the order that bats belong to and what does it mean? 4. What are the largest and smallest bats and where do they live? 5. How many different types of bats are there worldwide? 6. Bats are divided into two (2) suborders. What are their names? 7. Which suborder of bats uses echolocation and which suborder uses eyesight to find their food? 8. What is the diet of the Megabats? 9. What is the diet of the Microbats? 10. How many babies does a bat have each year and what are the babies called? 11. Find three Bible texts that mention bats. 12. Do bats hibernate or migrate for the winter? 13. Name the parts of a bat. 14. How many insects can a bat eat in an hour? 15. What are the two (2) main benefits bats provide for man? 16. Build or purchase a bat box, know the best place to put it and install it at a home, church, or your school. Record for 3 months what kind and how many bats have made it their home. |
Bat Honor Advanced Requirements
1. Earn the Bats honor. 2. What are caves, attics, bridges, or tunnels where bats hibernate called? 3. Give three (3) examples of colonizing bats. 4. Give three (3) examples of solitary roosting bats. 5. What is meant by delayed implantation? 6. How long is the gestation period for bats? 7. What is bat guano and why was it important during the War of 1812 and the Civil War? 8. What disease can be contracted from large quantities of guano? 9. What is the life-span of a bat? 10. Do all bats have rabies? 11. How good is the vision of microbats and megabats? 12. What North American bat is pictured on the honor? |
Some Useful Resources to Get Started
Bat Conservation International: https://www.batcon.org/
Austin Bat Refuge: https://austinbatrefuge.org/
Texas State University Texas Bats: https://www.depts.ttu.edu/nsrl/mammals-of-texas-online-edition/Accounts_Chiroptera/index.php
Texas A&M AgriLife Extension About Bats: https://agrilife.org/batsinschools/about-bats/
Merlin Tuttle’s Bat Conservation: https://www.merlintuttle.org/
Bat World Sanctuary: https://batworld.org/
TPWD Bat Watching Sites of Texas: https://tpwd.texas.gov/huntwild/wild/species/bats/bat-watching-sites/
Texas Department of Transportation Bats of Texas: https://ftp.dot.state.tx.us/pub/txdot-info/library/pubs/kids/bats.pdf
Department of the Interior 13 Awesome Facts About Bats: https://www.doi.gov/blog/13-facts-about-bats
TPWD Bat information: https://tpwd.texas.gov/education/resources/texas-junior-naturalists/bats
USGS Bat programs and information: https://www.usgs.gov/centers/norock/science/science-topics/bats
National Park Service Bat information: https://www.nps.gov/subjects/bats/index.htm
TCU Bat Monitoring Program: https://cse.tcu.edu/environmental-sciences/research/bat-monitoring-program.php
Texas A&M AgriLife Today About bats: https://agrilifetoday.tamu.edu/2024/10/08/millions-of-bats-call-texas-home-sweet-home/
TPWD and Texas Master Naturalists Acoustic Monitoring of Texas Bats: https://txmn.tamu.edu/wp-content/uploads/2024/02/Acoustic-Monitoring-of-Texas-Bats-A-Citizen-Science-Project-for-TMNs-.pdf
Smithsonian Bat Lab: http://www.noseleaf.org/
Books
Bats of Texas
by Loren K. Ammerman, Christine L. Hice and David J. Schmidly, Illustrated by Carson Brown
Texas Bats
by Merlin D. Tuttle
Bats: An Illustrated Guide to All Species
by Marianne Taylor, Merlin D. Tuttle
America's Neighborhood Bats: Understanding and Learning to Live in Harmony with Them
by Merlin D. Tuttle
The Lives of Bats: A Natural History
DeeAnn M. Reeder
The Secret Lives of Bats
by Merlin Tuttle
Bats in Question: The Smithsonian Answer Book
by Don E. Wilson, Merlin D. Tuttle (Photographer)
Bats of the United States and Canada
by Michael J. Harvey, J. Scott Altenbach, Troy L. Best
Austin Bat Refuge: https://austinbatrefuge.org/
Texas State University Texas Bats: https://www.depts.ttu.edu/nsrl/mammals-of-texas-online-edition/Accounts_Chiroptera/index.php
Texas A&M AgriLife Extension About Bats: https://agrilife.org/batsinschools/about-bats/
Merlin Tuttle’s Bat Conservation: https://www.merlintuttle.org/
Bat World Sanctuary: https://batworld.org/
TPWD Bat Watching Sites of Texas: https://tpwd.texas.gov/huntwild/wild/species/bats/bat-watching-sites/
Texas Department of Transportation Bats of Texas: https://ftp.dot.state.tx.us/pub/txdot-info/library/pubs/kids/bats.pdf
Department of the Interior 13 Awesome Facts About Bats: https://www.doi.gov/blog/13-facts-about-bats
TPWD Bat information: https://tpwd.texas.gov/education/resources/texas-junior-naturalists/bats
USGS Bat programs and information: https://www.usgs.gov/centers/norock/science/science-topics/bats
National Park Service Bat information: https://www.nps.gov/subjects/bats/index.htm
TCU Bat Monitoring Program: https://cse.tcu.edu/environmental-sciences/research/bat-monitoring-program.php
Texas A&M AgriLife Today About bats: https://agrilifetoday.tamu.edu/2024/10/08/millions-of-bats-call-texas-home-sweet-home/
TPWD and Texas Master Naturalists Acoustic Monitoring of Texas Bats: https://txmn.tamu.edu/wp-content/uploads/2024/02/Acoustic-Monitoring-of-Texas-Bats-A-Citizen-Science-Project-for-TMNs-.pdf
Smithsonian Bat Lab: http://www.noseleaf.org/
Books
Bats of Texas
by Loren K. Ammerman, Christine L. Hice and David J. Schmidly, Illustrated by Carson Brown
Texas Bats
by Merlin D. Tuttle
Bats: An Illustrated Guide to All Species
by Marianne Taylor, Merlin D. Tuttle
America's Neighborhood Bats: Understanding and Learning to Live in Harmony with Them
by Merlin D. Tuttle
The Lives of Bats: A Natural History
DeeAnn M. Reeder
The Secret Lives of Bats
by Merlin Tuttle
Bats in Question: The Smithsonian Answer Book
by Don E. Wilson, Merlin D. Tuttle (Photographer)
Bats of the United States and Canada
by Michael J. Harvey, J. Scott Altenbach, Troy L. Best