Tag Archives: Mexican Free-Tailed Bat

Brazilian Free-Tailed Bat

Brazilian Free-Tailed Bat (Tadarida brasiliensis, also known as the Mexican Free-Tailed Bat.

Brazilian Free-Tailed Bat
Image Copyright (c) Merlin D. Tuttle

Description: Body length about 3.4-4.3″, with a 12-14″ wingspan. The fur is uniformly dark brown or dark grey. The tail extends beyond the tail membrane between hind feet. Long narrow wings provide for fast flight.

Range: Migratory. Found from central North America to northern South America.

Habitat: Form large colonies in caves, buildings, under roof tiles and under bridges.

Diet: Forages mainly on moths. A farmer’s friend eating moths whose larva eats crops. Feed on migratory moths at very high altitude, up to 10,000 feet. Also eats flying ants, weevils, stink-bugs and ground beetles.

Behavior: Emerge at sunset in columns. Young left in large group. Each mother gives birth to one pup which she finds and nurses among the many young. Able to fly at about 5 weeks. Lifespan about 15 years. Predators include Red-tailed Hawk and other birds of prey, as well as cats and dogs which locate roosts and wait for emergence.

Risks: Colonies once numbering in the millions have been dramatically reduces in size due to human disturbance and habitat destruction of caves as well as problems with pesticide poisoning and deliberate eradication attempts.

Bat Terminology

Mexican Free-Tailed BatDefinition of terms when describing bats:

Calcara cartilaginous structure protruding from the ankle supports the back edge of the interfemoral membrane. The interfemoral membrane acts as a rudder and also reduces oscillations of the body through each wing-beat cycle

Forearm: longest bone in arm, with hook-like thumb at one end.

Keel: flap of skin on edge of tail which is a distinctive projection of the calcar. See photo of keel and calcar at: University of Michigan Museum of Zoology

Total lengthmeasured from nose tip to tail tip.

Premolars: are the teeth with points, just behind the canine. Molars are further back and are relatively flat.

Tragus: a projection surrounded by external ear flap, often stiffened with cartilage. Ours is a little blunt one, in front, center of ear, forming front of entrance to ear canal.