Mexican Free-Tailed Bat Photo by: Stephanie Martinez – Brewer (iNaturalist observation 30174609)
We conserve only what we love.
will love only what we understand.
will understand only what we are taught.
More than ever, bats need our conservation help. Understanding bats can change our perspective of these vital contributors to the world’s food production and ecological balance – to know them is to love them. This article will help reinforce existing knowledge or contribute to one’s bat knowledge repertoire.
With over 1,330 species, bats make up nearly one-quarter of all mammals worldwide. While most bats prefer the tropics, they can be found in rain forests, mountains, farmland, woods, and cities – everywhere except for the Arctic, Antarctica, and some islands. Only 48 species make their home in the United States. Of those, about 30 reside in Texas – more bat species than any other state. This article will keep it close to home, concentrating on the eight bat species that make Bexar County their home.
BEXAR COUNTY BATS
The Mexican Free-tailed, Hoary, Peter’s Ghost-faced, Eastern Red, Northern Yellow, Cave Myotis, Evening, and Tri-color bat make Bexar County their home all or part of the year. There are a few additional species found on the edges of the county or as accidentals. Many are cave dwellers like maternal colonies of Mexican Free-tailed bats, but others live in smaller clusters, family groups, or are primarily solitary and find homes in trees, buildings, and even leaf litter.
Bat Conservation International calls the Hoary bat the “George Clooney” of the bat world. This handsome bat’s hoary or grayish-white/frosted appearance is effective camouflage while living solitarily in forests. Only the Hoary bat and the Mexican Free-tailed bat are found in every county throughout Texas. This bat is the most widespread bat species in the Americas. However, they are seldom seen, preferring to live solitary lives in tree foliage.
Eastern Red bats are unique among local bats in that mothers often have twins, triplets, or even quadruplets each summer. Most other bats have one single annual pup. As its name indicates, their hair is a beautiful frosted reddish-orange – males darker in color than females. While sleeping in trees, these solitary bats resemble a dead leaf.
Northern Yellow bats range from all along the Texas coast to the Hill Country’s southern border. Their temperate coastal living affords them year-round activity. They’ll nest in Spanish moss, beneath hanging palm fronds, or in oak trees with plenty of open space to take flight. There is also a Southern Yellow bat, but these are found in Texas’ southernmost counties and are smaller in size.
Tri-color bats are the state’s smallest bat. Previously known as the Eastern Pipistrelle bat, this bat has distinctive brown, tan, and black tones within each hair. Feeding over waterways and ponds, these bats can catch an insect every two seconds. An unusually slow flyer, some say they remind them of a large moth. They can often be seen in Brackenridge Park, San Antonio.
Cave Myotis live in a variety of spaces and are often found roosting with other bat species. Typically, they forage for different insects, have lower flight patterns, and emerge after other species have flown for the night. Interestingly, ‘myotis’ in Latin for mouse ear. One early myth was that bats were flying rodents. Not only is this false, but bats are more closely related to humans than mice. They are in their own unique family, Chiroptera, meaning hand-wing in Greek.
Evening bats also share roosts with other species, especially Mexican Free-tailed bats. Female Evening bats can form colonies of 25 to 1,000 individuals but are also known to roost in tree cavities, behind loose bark, in buildings, and bat houses. These bats often stay year-round in warmer habitats, while our Bexar County Evening bats may migrate further south each winter.
Previously, the Big Brown bat was listed as living in Bexar County, but recent studies indicate their occurrence is rare. Peter’s Ghost-faced bat, once with a more southern range, is now found often enough to be considered a resident. They are rarely encountered by humans other than cavers.
OUR MOST FAMOUS BEXAR BAT
The most well-known and abundant of our local bats is the Mexican Free-tailed bat. This free-tailed bat gets its family name from its appendage that extends down from its flying membrane/wings. Its scientific species name, Tadarida brasiliensis, translates to ‘withered toad belonging to Brazil.’ Indeed, these bats extend far south from Mexico into Argentina and as far north as near Chicago.
Most of our Mexican Free-tailed bats live in Texas only from April to September each year. They migrate south into Mexico for the winter. Some other Bexar bats stay here year-round, going into a state of stupor, a slowing of their metabolism.
The largest colony of any mammal anywhere in the world is located just outside Bexar County north of San Antonio. Bracken Cave, now owned by the Bat Conservation International, is the maternal summer home to nearly 20 million Mexican free-tailed bats – one-fifth of all Mexican Free-tailed bats summer in Texas each year. Pups, as baby bats are known, cluster together while their mothers fly out to feed each night – as many as 500 pups per square foot of cave ceiling space. Bats have occupied this cave for over 10,000 years. Male Mexican Free-tailed bats roost together in smaller groupings not only in caves, but in buildings, bridges, forests, and man-made bat houses.
Because of their close living quarters, Mexican Free-tailed bats in caves produce a massive amount of guano. This natural fertilizer and previous component in gun powder, has been mined from the Bracken Bat Cave since long before the Civil War. Bats here deposit approximately 50 tons of guano annually.
Bat Conservation International members and groups can schedule emergence viewings. While not open to the general public, many other locations throughout the state are. Texas Parks and Wildlife has a publication listed at the end of this article outlining viewing locations and arrangements throughout the state.
Not only are the Mexican Free-tailed bat Texas’ official State Flying Mammal, but they are also our Capital Austin’s official animal. Austin proudly calls itself the Bat Capital of America. With 1.5 million bats calling downtown Austin’s Congress Avenue Bridge their summer home, it’s now the world’s largest urban bat colony. The Bat Conservation International moved their headquarters to Austin in 1986 in part to help protect this colony that was once thought to be a public nuisance. These bats are now revered, bringing in an estimated $10 million every year in tourist dollars while helping control destructive insects. Their nightly emergence with the city’s skyline in the background draws tens of thousands of visitors each summer.
We have our own urban Mexican Free-tailed Bat colony in downtown San Antonio under Highway I-35 bridge, where it crosses the San Antonio River near Camden Street. The half-million male bats emergence to feed around dusk can be seen from May – October. “Bat Loco Bash,” a festival sponsored by the Bat Conservation International, Texas Park and Wildlife, and the San Antonio River Authority / San Antonio River Foundation, is held every August to help celebrate not only our local bats but to educate the public on the conservation of all things bat-related. Food, games, entertainment, education, and of course, bat-flight viewing are all part of the festivities.
Mexican Free-tailed bats eat a wide variety of insects, but their favorites are several species of moths whose pupa stage cause agriculture crop damage, i.e., corn earworm/cotton bollworm moths. One of these moths can lay up to 1000 eggs – each capable of growing into voracious crop eaters. Other insects enjoyed by our Bexar bats include beetles, leafhoppers, ants, mosquitoes, and flies.
WHY ARE BATS IMPORTANT?
Bats across the U.S. save farmers over $23 billion a year by reducing crop damage and the need for pesticides. It is estimated that just the Bracken Cave bats, eat 200 tons of insects nightly during the growing season. To put that into perspective, 200 tons equates to the weight of six fully loaded concrete trucks or 50 Asian elephants. It is estimated by Bat Conservation International that just 150 Big brown bats can eat enough cucumber beetles each summer to protect farmers from 33 million of these beetles’ rootworm larvae saving a billion dollars annually.
With most of our agriculture located south of San Antonio, the Bracken bats fly high over the city every night to gorge on airborne insects that the bats find through echolocation – the sending out of high-frequency calls that bounce off the insect and help bats zone into their whereabouts. Mexican Free-tailed bats can fly up to 10,000 feet (nearly two miles!) above the ground. While not the most agile species of bats, Mexican Free-tailed bats are one of our fastest mammals, clocking in at more than 99 miles an hour.
All our Bexar County bats are insectivores, as are two-thirds of all bat species worldwide. As important as insectivores are, other bats play an equally vital ecological role in pollinating plants and dispersal of seeds. Bananas, mangoes, peaches, avocados, cashews, dates, and figs are just a few of the 450 economically important products that rely on bats. Pipe organ and saguaro cacti and agave plants used in tequila production would not exist without bats. These fruit or nectar-eating bats account for another one-third of bats. A small one percent of bats eat fish, mice, frogs, rodents, or other small vertebrates.
AMAZING BAT FACTS
Other non-Bexar bats are worth mentioning simply because of their fascinating contributions to folklore, science, and medicine. In addition, knowing just a bit more about bats in general helps eliminate misunderstandings about these fascinating creatures. The old saying “Blind as a bat” is entirely untrue – they have excellent eyesight. They don’t become entangled in human hair – again, an old falsehood. They seldom transmit disease (even rabies) to other animals or humans.
Bats range in size from the Bumblebee bat (Thailand), about a penny’s weight, to the Flying Fox bat (Asia, Africa, Australia, and the South Pacific) with a six-foot wingspan. For comparison, the Mexican Free-tailed bat has an 11-inch wingspan. The Flying Fox is so named because their faces resemble those of little foxes. As fruiteaters, they do not use echolocation. They instead use their keen sense of smell to find ripe fruit.
Fishing bats can echolocate on a minnow’s fin that’s as fine as a human hair sticking up above the water’s surface.
There are only three species of Vampire bats and all are in Mexico, Central or South America – none in the United States. Only one of the species, the Common Vampire bat (Desmodus rotundus) feeds on the blood of mammals (cows, sheep, pigs.) The other two species prefer birds. There’s no sucking of blood involved. Rather, the bat makes a painless small cut into the prey with their razor-sharp front teeth. They then proceed to lap about a tablespoon of blood without the “donor” even waking. The anticoagulant from the bats’ saliva helps to keep the blood flowing until the meal is finished. Scientists are using the knowledge gained from this research to help human heart and stroke patients.
Bats help the medical field in other areas because they feed on mosquitoes that spread diseases – Dengue Fever, dog heartworm, malaria, and yellow fever.
Bats should never be handled by anyone other than licensed professionals. If found on the ground, they may be sick, injured, or are juveniles needing a rest or the ability to find a tall structure to climb/launch once again in flight.
Many challenges face the well-being of bats throughout the world. These include the reduction of native plants needed for insectivores, loss of habitat and environmental pollution to expanding human populations, being hunted for food, extermination due to unnecessary fears, wind turbines, and White-nose Syndrome – a disease killing millions of bat species as they hibernate. Four species in the United States are listed as ‘endangered.’ Another species is ‘threatened.’ Bat Conservation International is working with government and private associations to help with each of these issues.
FOR MORE INFORMATION
An internet search will provide you with much more information regarding our world’s bats.
Here are a couple of links to get you started:
- Bat Conservation International – www.batcon.org
Please consider membership to this wonderful organization. You and your guests will be eligible for annual bat viewing events at Bracken Cave!
- Texas Parks and Wildlife publication – Bat Watching Sites of Texas (includes San Antonio’s own Camden Street Bridge bat viewing information)
- Bat Publications – Department of the Interior / USGS
A project of the Alamo Area Master Naturalists working with the Phil Hardberger Conservancy and Alamo Group of the Sierra Club
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