Nature's Neighbors ~ Mexican Free-tailed Bat

Mexican free-tailed bats are a medium-sized bat with short, velvety, reddish to black-colored fur, broad ears, large feet, and the end of its tail extending beyond the edge of it’s tail membrane, hence the name “free-tailed”.  They occupy a wide variety of habitats, ranging from desert communities through pinion-juniper woodland and pine-oak forests, at elevations from sea level to 9,000 feet or more. The largest U.S. populations of free-tailed bats live in the West.  The densest concentrations are found in Texas where they form maternity colonies which are found in limestone caves, abandoned mines, under bridges, and in buildings, but smaller colonies also have been found in hollow trees. It is estimated that 100-million Mexican free-tailed bats come to Central Texas each year to raise their young, the largest colony is currently found living in Bracken Cave near San Antonio, Texas, totaling over 20 million.  Nursing females require large quantities of insects that are high in fat, which they obtain by consuming egg-laden moths.

The 100 million free-tailed bats living in Central Texas caves consume approximately 1,000 TONS of insects each night.  Researchers use Doppler weather radar to watch emerging bats ascend to altitudes of 1,000-10,000 feet to feed on migrating cotton boll worm moths, army cut-worm moths, and other costly agricultural pests that migrate north from Mexico. These migratory moths hopscotch across the country each year, reaching rich agricultural land as far north as the Canadian border. The cotton boll-worm moth (a.k.a. corn ear-worm moth) alone, costs American farmers a billion dollars annually.   Although the ecological and economic impacts of large colonies are most obvious, even small colonies of bats can significantly impact local insect populations. Mexican free-tailed bats also consume enormous quantities of insects over woodlands and forests, likely including many additional pests.  

The impact of second hand pesticide poisoning of free-tails and other bats should not be underestimated, but it seems certain that this is probably not the major stress responsible for the decline of free-tailed bat populations. In a recent review of the effects of environmental contaminants on bat populations, it seems quite evident that much of the decline in free-tailed bat populations is directly due to human disturbance and roost site destruction.  It is important to preserve those colonies which still thrive. The apparent good condition of several large roosts is clearly due almost entirely to the fact that access to them is restricted by land owners who appreciate the unique resource with which they are entrusted.

Current initiatives by Bat Conservation International, The Nature Conservancy, and the Marbach family to ensure continued protection of the site of the largest known roost in Bracken Cave are to be applauded.

So the next time that you bite into that juicy ear of corn or ripe apple, remember a bat probably  played a part in bringing it to you!