A novel multidisciplinary study is quantifying the economic impact of bats, specifically the enormous colonies of Mexican free-tailed bats that migrate each spring to south central Texas.Led by Geography Professor Cutler Cleveland, director of the Center for Energy and Environmental Studies, CAS Biology Professor Thomas Kunz, and colleagues at the center, the National Science Foundation-funded effort also includes entomologists, agricultural scientists, and biologists who specialize in modeling animal populations from institutions throughout the United States and in Mexico.

To get an accurate picture of the scope of the bats' impact, Cleveland and Kunz use a novel thermal infrared video camera correlated with Doppler radar to count and track the bats, who eat up to half their body weight in insects every night. On one evening they counted more than 1.5 million bats emerging from a single cave and tracked them as they disbursed over a distance of more than 10 kilometers.

In calculating the economic value, Cleveland notes, it is necessary to consider some factors that are fairly evident, such as the value of the crops undamaged by the insects eaten by the bats and the cost of chemicals that do not need to be used. But there are other, less evident savings. By decreasing the need for pesticides, insects are less likely to become resistant, and the cost of developing new, stronger pesticides is avoided. Also, fewer fish and wildlife die from pesticide runoff.

The bats also have an impact through ecotourism. Visitors gather every evening at the mouth of the cave to witness the colony of bats as they emerge on their nightly search for food. At another site, right in the middle of Austin, Texas, a colony of bats roosts under a bridge, again drawing hundreds of tourists each night, who spend money that supports the local economy. The state of Texas even designs new bridges with roosting habitats built into the design.