Warmer Days Bring on Bats
Ro Wauer, March 23, 2003, The Victoria Advocate, © 2003
Bats are some of our most beneficial creatures! These nighttime fliers appear in South Texas each spring when the temperatures become warm enough for nighttime flying insects. That is when these flying mammals are most appreciated. They have enormous appetites. A single bat colony can consume billions of insects every summer night.
The majority of the bats that we find in our spring and summer skies are migrants, coming north, like the Neotropical bird migrants, each spring. Others remain with us year-round, hibernating in dark, protected locations during the colder winter months. Those hibernating species go into a torpor state during cold weather when their metabolism is much reduced to conserve energy. Their body temperatures drop to just above freezing. But as soon as outdoor temperatures climb back into the 60s and a food supply becomes available, they will awaken and begin their nighttime flights.
A feeding bat is able to capture some of the tiniest of flying insects. They do this by the use of echolocation, high-frequency sounds that they emit in flight. The sound bounces off objects that are then received by the bat that is able to zero in with pinpoint accuracy to capture its prey. This ability, as well as bat's preference for dark locations, suggests that that they are blind. But that assumption is incorrect. Bats are not blind. They can see everything but color, and they can detect obstacles as fine as a human hair.
Another misconception about bats is that the majority carries diseases, including rabies. Although all carnivores (meat-eaters) can contract rabies, bats have the worst reputation. Yet, only 40 U.S. residents are known to have contracted rabies from bats in the past 50 years. To put that into perspective, 900 Americans annually die in bicycle accidents, 150 in accidents caused by deer, 20 from dog attacks, and 18 in lawn mower accidents. Less than one-half of one percent of bats become infected with rabies and these rarely attack humans.
Texas has 32 species of bats, and these flying mammals can be found in every Texas County. But not all of the 32 species occur throughout the state. As might be expected, there are more species in the southern portions of the state, especially in the Big Bend Country and along the Lower Rio Grande Valley area. Only six species are known from the Central Gulf Coast region. Those six species include the eastern red bat, hoary bat, northern yellow bat, evening bat, eastern pipistrelle, and Mexican free-tailed bat.
The eastern red and hoary bats roost in foliage during the daylight hours, flying at night and feeding principally on moths. They also take various beetles, assassin bugs, planthoppers, leafhoppers, and spittlebugs. Northern yellow bats roost overnight in Spanish moss, and they seem to prefer flies, mosquitoes, flying ants, and may even take damselflies and dragonflies.
Evening bats and eastern pipistrelles roost in tree cavities, behind loose bark, in buildings, and in bat houses. A colony of 300 evening bats was documented to consume approximately 63 millions insects per summer, especially spotted cucumber beetles. Pipistrelles usually feed over water and along wooded edges; they can catch an insect every two seconds.
Mexican free-tailed bats are our most numerous species. Free-tails roost in caves, crevices, buildings, bridges, and bat houses. Backen Cave, near San Antonio, hosts about 20 million individuals, considered the largest aggregation of warm-blooded animals on Earth. The species also inhabits numerous other Texas caves, including Eckert James near Mason, Frio near Garner State Park, and Stuart Cave in Kackapoo Cavern State Park. The species also inhabits Congress Avenue Bridge in Austin and Devil's Sinkhole near Bracketville.
Bats are not only extremely beneficial, but also one of our most fascinating creatures. More information on bats can be obtained from a new little, illustrated book, "Texas Bats" by Merlin Tuttle, published by Bat Conservation International, available for $9.95 in most bookstores. You can contact the organization on line at www.batcon.org or at P.O. Box 162603, Austin, Tx 78716.