A Texas Visitor Heads South for Winter

Statement

A Texas Visitor Heads South for Winter

John Cornyn

Every fall, as the first cold-air ‘norther swings into Texas, millions of part-time Texas residents ride the cold front south toward Mexico. We will all look forward to their return next spring.

Texas is the summer home to 31 species of bats, the most of any state. These bats are important links in our ecological balance. Their impact on our state is significant.

Bats consume an estimated six to 18 million tons of insects every year, making Texas more livable and providing a boost to farmers all over the central United States.

The Mexican freetail bat, partial to Central Texas, loves to eat corn ear moths, flying ants, army worms and other pests that also migrate north in the spring. The bats follow their food supply in the spring, migrating into Texas in March and April on the heels of moth swarms.

The U.S. food supply is indebted to Texas bats. Migrating moths eaten by bats in Texas cannot later attack cornfields in Kansas and Iowa. The positive impact on agriculture alone runs into millions of dollars every year.

Female bats often settle in big maternity sites, such as the Bracken Cave north of San Antonio, now owned by Austin-based Bat Conservation International. It's the largest bat colony—and arguably the largest gathering of mammals—in the world. Each female typically produces a single pup in mid-June. The newcomers are flying by August, and by late October, most of the 20 million bats are heading south for the winter.

The world's largest urban bat habitat is under the Congress Avenue bridge in central Austin. Most of the 1.5 million bats there are female. Male bats typically set up separate bachelor roosts elsewhere after mating, and do nothing in raising the offspring.

Tourists come to Austin from all over the world to watch insect-seeking bats pour out every summer evening at dusk. The city calculates its annual bat tourism revenue at $10 million.

The bats typically locate insect prey using echolocation—zeroing in with their sharp, pointed ears. An adult bat is about four inches long, with a 12-inch wingspan, and can consume one quarter of its weight in insects every night. The Bracken Cave bats alone consume up to 250 tons every day.

There are surprising gaps in our knowledge of bats. We know they sometimes fly as high as 10,000 feet in search of food. We also know that various species enjoy virtually every insect imaginable—including beetles, flies, termites, mosquitoes, frog hoppers and leaf hoppers. Some even eat scorpions. The bats consume insects that attack our entire range of fruits and vegetables, from asparagus to tomatoes.

Historically, bat counts have been mere estimations. But scientists have recently begun using infrared cameras (which don't disturb the night flying mammals) to get a more accurate count.

It was once thought that a mother bat returning at night from an insect hunt merely nursed the nearest pups amid hundreds of thousands in a cave. But we now know the mothers recognize and locate their own pup through its unique cry and smell.

The Texas Department of Parks and Wildlife has a summary of the best "Bat Watching Sites of Texas" on its Internet site. Most are near the Hill Country area, including the Devils Sinkhole Natural Area, summer home to three million freetail bats.

But good bat-watching spans the entire state. Up to a half-million bats can be found in the abandoned Clarity railroad tunnel at Caprock Canyons State Park in the Panhandle. Almost that many roost year-round under the Waugh Drive Bridge, a few miles west of downtown Houston.

Bats have a frightening image in our popular culture, and periodic incidence of rabies means that caution should be exercised in any close encounter with humans. But bats are also a fascinating element of our land, a small part of what makes Texas great.

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