- Author: Robert J Keiffer
The Mexican free-tailed bat ( or Brazilian free-tailed bat) (Tadarida brasiliensis) is one of the most widespread mammals in the Western Hemisphere. The UC Hopland Research & Extension Center is near the northernmost extent of their summer range (southern Oregon). This is the bat species that is famous for large colony roosting in such places as Carlsbad Caverns in New Mexico where millions of bats are observed by public visitors as they exit their cave roosts at dusk. Migratory in nature, the Mexican free-tailed bat only occurs here in North America during the summer months, and migrates to South America during the winter months, although the precise winter range is not well understood yet (they are NOT in the Amazon Rain Forest).
Usually roosting in caves, this species will sometimes roost in buildings (there is one barn at HREC where they traditionally roost). They hunt insects such as moths, mosquitoes, beetles, flies, true bugs, wasps, and flying ants by using echolocation and tend to forage at higher altitudes than other bat species. Preliminary high-frequency recordings near UC-HREC have shown that they forage over chaparral habitat at the 3000' elevation range.
The tail of this bat species extends beyond the uropatagium (skin flap that connects the hind legs) which places them into the "free-tailed bats" family group called Molossidae. Their echolocation calls are partially audible (within our hearing range) and sounds like rapid "clicks".
Future research is really needed in order to better understand how this bat species and other bat species utilize the Mendocino County vegetation types.