Cave in Texas is home to one of the largest bat colonies in
the world with up to 40 million mexican free-tailed bats in
residence. They emerge at dusk taking 2.5 hours to do so and
feed at up to 10,000 feet on insects that otherwise would destroy
the local crops. Because of this they save the Texas economy
millions of dollars each year. Each mother returning to the
cave can find her own single baby, amongst millions of others,
just by its call signature and smell.