At the entrance to Carlsbad Caverns just outside Roswell (NM), hundreds of people wait for over 300,000 Mexican freetail bats to leave their roosts at about sunset. The bats then fly over 25 miles to a river area to consume almost 20 tons of insects in a single evening.

This specie of bat has longer, narrow wings for long distance travel--they migrate to central Mexico in the winter. Because of this, they are not good up-and-down flyers. To exit the cave, the must fly in a circle, slowly moving upward until they clear the lip of the surrounding rocks. When they return, they fly just above the cave opening, then close their wings to plummet straight down. They re-open their wings just before the cave floor and return to their roosts. They consume one-half of their body weight (about one ounce) in insects each night.