Brazilian Free-Tailed Bat
This bat is well known for its large colony that summers in the San Luis Valley.
About This Species
This migratory species of bat is small and gray-brown with long, narrow wings and a tail that extends well beyond the membrane between the legs.
Living with Bats
There are 18 species of bat that call Colorado home. These amazing mammals are not only fantastic insect control, but are also valuable pollinators. Learn more about how humans and bats can live in harmony in our guide.
Bat Conservation
Bats remain one of the most mysterious land mammals, especially in Colorado, where 18 species spend at least part of the year. For example, the little brown bats in our state seem to hibernate differently than those on the east coast, and we are constantly learning about their whereabouts, habitats and behaviors. Our current research suggests that bat populations in Colorado are doing quite well.
One little brown bat can eat up to 18,000 small insects (like mosquitoes) each night. Their economic impact is estimated to be billions of dollars, and much of the agricultural industry relies on their insect control.
Beyond their economic impact, bats flaunt some impressive adaptations. They are the only mammal that truly flies, which requires a very unique anatomy. Their upside-down lifestyle requires adaptations in their “feet” to consistently grip. If people hanged upside down for even an hour, we’d lose consciousness; bats have developed amazing blood pressure accommodations to fit the lifestyle.
We are currently involved in a monitoring partnership called the North American Bat Monitoring Program (NA Bat). The program utilizes acoustic surveys to collect information on bat populations without interfering with their behaviors. We also are using PIT tags, like the chips put in household pets, to monitor a number of maternity sites. While data collection will take years, we’ve already learned new information about Colorado’s bat population, the most heartening of which is that the population appears larger and more widespread than we’d thought. This is an excellent start to learning more about the species, but we’ve got lots of problem-solving and technological innovation left to do.
Our priorities also include learning more about bats so that we are prepared for the potential spread of White-nose Syndrome. Finding and monitoring bats is crucial to this effort, but also comes with its own challenges. Because bats are small, flying mammals, much of the equipment used to track other species is too heavy for them. And during the winter, Colorado bats are very elusive, choosing to hibernate in small groups often in locations that are inaccessible to people.
More Information:
Physical Characteristics
Individuals weigh eight to 12 g and have short ears that almost join at the midline of the forehead. Wingspread is approximately 300 mm, total length is 90 to 105 mm and the forearm is 36 to 46 mm long.
Range
Brazilian free-tailed bats range from southern Oregon and Nebraska to South America. In Colorado, this species seems confined to the southern half of the state.
Previously the Brazilian free-tailed bat was considered only a wanderer in Colorado, but it is now known to be a summer resident.
Habitat
The Brazilian free-tailed bat roosts in caves and mines and is often found in man-made structures. The animals are highly social. In Arizona, New Mexico and Texas, nursery colonies of 10 to 20 million individuals have been reported. Males generally form small colonies farther north, although a colony in Colorado has an estimated population of as many as 250,000 individuals. This bat does not hibernate in Colorado.
The species is highly migratory and travels south to Mexico and Central America for winter. There may be distinct migratory pathways. Some bats apparently live to be 15 years old, but most have a considerably shorter life span.
Diet
This bat eats mostly small moths, although beetles, bugs, mosquitoes and wasps are also taken. The large population of this species in south-central Colorado consumes tons of insects each year. The bats forage high over large open areas, leaving their roosts in a flight formation that resembles a long plume of dark smoke. They may forage up to 40 miles from their day roosts.
Reproduction
Brazilian free-tailed bats breed on their winter ranges. Gestation is 90 to 100 days, and a single young is born in mid-June or early July. Although most young are born south of Colorado, a few are produced here. At birth, infants weight 25 percent of the mother's weight, about 2.5 to 3 g.
For many years it was believed that mothers in colonies of hundreds of thousands or even several million females probably did not nurse their own young, but simply fed the first young to grasp the nipple. However, it has now been demonstrated that females locate their offspring by auditory and olfactory cues. Young begin to fly at about 5 weeks and are weaned shortly thereafter.
Threats to Species
- Predators include owls, kestrels, various hawks, raccoons, skunks and snakes.
- White-nose syndrome