Ranging from the southern half of the United States to Central America, the Mexican free-tailed bat roosts in the largest mammalian colonies in the world. The species’ summer population is largely concentrated in 12 caves, the rest living mostly in buildings and under bridges.
The largest summer colony is in Bracken Cave near San Antonio, Texas, where as many as 20 million individuals congregate. The Nature Conservancy protects one of the largest bat nurseries in the country, Eckert James River Bat Cave Preserve in Mason County, Texas, where 4 million females gather every year. Meanwhile, more than one million bats roost under the Congress Avenue bridge in Austin, Texas, forming the largest urban bat colony in North America. Most populations migrate south to Mexico and Central America in the winter.
The Mexican free-tailed bat preys on flying insects, consuming its body weight in mosquitoes and agricultural pests like cutworm and corn borer moths each night. It is estimated that the Bracken Cave population alone consumes 200,000 to 250,000 pounds of insects each night. Usually a bat will feed within 50 miles of its day roost, but some may range as far as 150 miles.
Mating between February and early April, females produce a single pup, usually in June. The young roost in dense masses, sometimes as many as 500 pups per square foot of cave wall. Mothers are able to locate their young within inches, remembering location and responding to pups’ calls and unique scents. The pups drink nearly a third of their body weight in milk daily, and begin flying after about five weeks. Females typically return to their natal roost to breed.
In addition to the Eckert James River Bat Cave, the Conservancy also protects a number of smaller bat caves on private properties in Texas through conservation easements and conservation buyer deals.
Tidbit: A Mexican free-tailed bat can fly at speeds reaching 60 mph.