The fur color of these bats is reddish to dark brown or can also be grey. Mexican Free-tailed bats have broad, black ears and the wrinkled lips that are characteristic of this family. The terminal half of the tail is not connected to the bat's body. These bats are monomorphic. They feed on flying insects such as mosquitoes, flies, beetles and moths.
Bats use echolocation to find their prey items.
Mexican Free-tails consume their body weight in food each night. With roosts possibly containing millions of bats, it is estimated that 250 tons of insects can be consumed every night by these bats. While female bats are nursing their young they consume twice the amount of food that a non-lactating bat will consume. Upon arrival the males and females mate and then divide into bachelor and nursery colonies. Males are two years old when they mate and females can be as young as one year old when they give birth to their first pup.