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Tuesday, March 25, 2014

Beneficial Bats

Mexican Free-Tailed bats

For millions of years, bats have long played essential roles in nature’s system of checks and balances.  Once extremely abundant, they dominated the night skies.  In more in recent times, however, their declining numbers reflect the ongoing compromise of the overall health and stability of our environment.

Bats are mammals, but such unique ones that scientists have put them in their own group, the Chiroptera, or “hand-wings.”    Occupying a large variety of habitats ranging from desert communities through pinyon-juniper woodland and pine-oak forests, there are 26 species of bats known to occur in Texas, but none is more commonly seen than the Mexican Free-Tailed bat.  These bats migrate each spring from Central Mexico to the same areas in the southwestern US, with the densest   concentrations occurring in Texas.  In fact, it is estimated that 100 million come to Central Texas each year to raise their young.   At approximately 1.5 million individuals alone, the Mexican Free-Tailed bat colony living under the Congress Avenue Bridge is the largest urban bat colony in the world!

Ranging from dark brown to grey, Mexican Free-Tailed bats are not much to look at, and some have described them as looking like “little gnomes with an overbite.”  They get their name from their tail, which protrudes freely beyond the wing membrane.  But don’t let their plain appearance fool you – these are the “speedsters of the bat world,” and they have been clocked flying at 60 mph using tail winds, and flying higher than any other bat at altitudes over 10,000 feet.  Mexican Free-Tailed bats are mostly migratory, with their arrival beginning in late February and their departure beginning in late October, triggered by the passage of strong cold fronts from the north.  Not all bats leave, however, and for unknown reasons several thousand of them stay behind each winter.  

Comprised mostly of females, the Austin bat colony sees an explosion of births in early June, when each female gives birth to a single baby bat, or pup.  At birth they already weigh one-third of their mother’s body weight, and are nursed by their mother who locates them among the thousands by each pup’s distinctive voice and scent.  In 5 weeks time the pup learns to fly and begins hunting insects on its own.  Aside from being fun to watch, bats make our world a better place to live.  They are gentle and incredibly sophisticated animals, and on each nightly flight out from under the bridge, they consume between 1,000 and 2,000 tons of insects (including agricultural pests)!  

Unfortunately, in spite of the popularity of the Austin bat colony, bats remain to be the world’s most endangered and least appreciated animals.  While bats suffer from environmental pollution and habitat loss like other wildlife, persecution from humans remains a primary cause for their decline.   Their colonies represent the most dense aggregations of mammals present in a limited number of locations, and combined with a low reproductive rate, recovery from the destruction of a large colony would be very slow.  As such, it is important to preserve those colonies that still thrive, and with the help of organizations like Bat Conservation International and The Nature Conservancy, along with private landowners, this unique resource and their habitat can be protected. 

Each summer night, when you join the hundreds of people gathered to watch the Mexican Free-Tailed bats emerge from their concrete roost in downtown Austin, you are witnessing one of nature’s most rare & awesome spectacles!