Background for Teachers
Hanging Around with Bats
TPW Magazine, October 2008
Texas happens to be the battiest state in the country. It is home to 31 of the 47 species of bats found in the United States. Not only does it hold the distinction of having the most kinds of bats, it also boasts the largest known bat colony in the world (Bracken Cave near San Antonio), and the largest urban bat colony (Congress Street Bridge in Austin). Visitors from around the world flock to Texas to enjoy public bat-viewing at several locations throughout the state. In 1995, Mexican free-tailed bat joined the longhorn and the armadillo as official state symbols. The Texas State Legislature named the Mexican free-tailed bat as the "state flying mammal."
The Truth About Bats
Contrary to old myths, bats are not blind, will not get tangled in your hair, and are not flying rodents. Bats do not have feathers or hollow bones like birds. Bats are mammals; they have fur, are warm-blooded, bear live young and produce milk for its young.
The morphology of bats is surprising. Their wings are actually arms and hands with elongated finger bones. A thick membrane of skin between fingers creates the wing. Unlike birds or even flying squirrels, bats cannot glide. Bats must constantly flap their wings to stay in flight. When classified, these mammals are in their own order called Chiroptera (pronounced kye-rop-ter-a), meaning hand wing. Bats are the only true flying mammals.
Most small mammals produce many young, but most species of bats produce just one offspring per year. Only a few species, such as the red and yellow bats, produce two, three or four young. Young are born in May or June. The young are cared for by the mother in nursery colonies. These colonies vary in size by species and location, with as few as 10 to millions in! Young bats learn to fly within two to five weeks. When bats are weaned varies by species, but is generally at one to two months of age. Surprisingly, bats live for a long time for a small mammal. In the wild, they can live 15 or more years. Some bats have been known to live as long as 30 or 40 years.
Although bats can see quite well they also use echolocation or sonar. Bats send out ultrasonic pulses from their nose or mouth, mostly inaudible to human ears, at a rate of a few to 200 per second. These sounds bounce off surrounding objects and back to a bat's ears helping it to navigate and find food, even in the dark. Using echolocation, bats can avoid obstacles no wider than a piece of thread. The squeaking sounds people can hear from bats are made between mothers and pups and aren't considered echolocation. (See the fascinating study on bat communication on the Research page.) In the magazine's "Anatomy of a Bat" picture, notice a part of the bat ear called the tragus. It's the projection extending over the ear canal. In bats that echolocate, the tragus is very large. There is speculation that the large tragus may play a role in echolocation. Human ears have a small tragus.
Bats that prey on insects snatch them by mouth or scoop them into their tail or wing membranes. They then reach down and take the insect into their mouth. This gives bats an erratic flight. One of our Texas bats, the pallid bat, feeds on centipedes and scorpions crawling on the desert floor. Texas's pollinating bats slip their long tongues into the flowers to drink nectar. Bats drink on the wing and need clean, unobstructed drinking water sources.
Bats are adapted for hanging upside down. Their hind limbs are rotated 180 degrees so that their knees face backwards. They hang by their legs and use the claws on their toes to support their weight. Locking tendons in the toes allow the bats to hang without expending energy.
Where Bats Live
Texas bats can be found in caves, cliff crevices, bridges, tree foliage, snags, hollow trees and occasionally buildings, especially where there is habitat destruction going on in an area. It's very important that you never touch a bat! Bats are protected by the state of Texas in their natural habitat.
Benefits of Bats
Insect-eating bats eat primarily moths and other bugs, many that are harmful to agriculture. Dr. Merlin Tuttle, in his book Texas Bats, notes a study of 150 big brown bats that, in one summer, ate 600,000 cucumber beetles, 194,000 scarab beetles, 335,000 stinkbugs and 158,000 leafhoppers, all of them pests that damage crops and gardens.
Some bats such as the Mexican long-nosed and long-tongued bats are important pollinators and seed dispersers. Many of our everyday products, such as tequila, wild bananas, balsa wood and allspice to name a few, come from bat-dependent plants. Texas's pollinating bats are in far south and far west Texas.
In a speech entitled "Science Connects: How Discovery Drives Our Global Future" by Dr. Arden L. Bement, Jr., Acting Director, National Science Foundation, commented on the impact of Texas bats. "Let's shift the biocomplexity focus to bats – in this case, many millions of them, in south-central Texas. Researchers are using advanced infrared and Doppler radar-imaging to model the population density and foraging behavior of Brazilian free-tailed bats. Bats from Texas caves provide pest-control services for crops such as cotton and corn. One local cave may host more than 20 million bats. In fact, bats from two caves protect the cotton crop to the tune of $258 million annually, a benefit previously without a price-tag. This same species consumes enormous numbers of insects all summer long across the southern United States. Such linkages between ecology and economics show how biocomplexity's integrative approach comes full circle – revealing the web of relationships that sustains both natural and human activities."
And if this wasn't enough, how about the uses of bat guano? This is a highly-valued fertilizer, but did you know it was actually used during the Civil War to make ammunition? Read more about this and other fascinating articles on the Research and Further Reading page.
TPWD Factsheets on bats featured this month:
- Brazilian (also called Mexican) free-tailed bat
- Pallid bat
- Mexican long-nosed bat
- Mexican long-tongued bat