Brazilian free-tailed bats are medium-sized bats with brown fur and big ears. They have short noses and wrinkly upper lips. Like other free-tailed bats, their tail goes past the skin that stretches up to it from their wings. They have strong legs and are good at climbing. Their wings are long, narrow, and pointed. This makes their bodies specially designed for quick, direct flights. Like other North American bats, they lower their body temperature and energy use every day by deeply resting. This is called torpor, which is a kind of hibernating. (Gannon, et al., 2005; Jones Jr. and Manning, 1992; Wilkins, 1989)
Brazilian free-tailed bats are found throughout North and South America. They are found in large parts of the United States, and also in Mexico, Central America, Brazil, Chile, and Argentina. In the United States, they are found from southern Oregon to Nevada, east to North Carolina and southwestern Virginia. In the last 50 to 100 years, their numbers have declined, possibly because of habitat loss, damage to resting locations, and pesticides. (Cranford and Fortune, 1994; Gannon, et al., 2005; Wilkins, 1989)
Brazilian free-tailed bats are found in different environments like caves as well as structures built by people like bridges and attics. They are most often found in caves that have large rooms and high ceilings, but also roost in hollow trees. They roost in these locations, which is when they hang upside down to rest or sleep. In these roosting locations, they nest, breed, and interact with each other. (Wilkins, 1989)
Male Brazilian free-tailed bats have different behaviors during the breeding season. Females gather together in maternity groups, which have both female bats and their young. Maternity groups in caves are large, and maternity groups in structures built by humans like bridges and buildings are smaller. Males make noise and mark territories to attract mates. Males and females call to each other, and single each other out. Once they are paired, they move away from the group. Males and females can have more than one mate. (Gannon, et al., 2005; Keeley and Keeley, 2004; Krutzsch, et al., 2002; Wilkins, 1989)
Brazilian free-tailed bats breed once a year. They mate in the spring, and then the pups grow inside the females for 11 to 12 weeks. Females usually have one pup per year. They give birth upside down, which takes about 90 seconds. Then, it takes the newborn bats 10 to 15 minutes to find their mother's milk. In a group of Brazilian free-tailed bats, the number of males and females in about the same. After nine months, females are grown up. After two years, males are grown up. (Gannon, et al., 2005; Krutzsch, et al., 2002; Wilkins, 1989; de Magalhaes and Costa, 2009)
Mothers leave their pups in a large group, so they have to use smells and calls to tell which ones are their young. Young Brazilian free-tailed bats can pick out their mother's scent, but they will try to get fed by any females in the group. The young get milk from their mothers every day. They are able to eat other foods after they reach adult size. After 4 to 7 weeks, they are independent of their parents. Their milk is 28% fat, which is the highest fat content of any bat. This helps their pups to grow fairly quickly. (Gannon, et al., 2005; Kunz and Robson, 1995; Loughry and McCracken, 1991; Wilkins, 1989)
The record for the longest life of a Brazilian free-tailed bat in the wild is over 8 years old. About 70 to 80% of adults survive each year. The longest reported life in captivity was 12 years. (Gannon, et al., 2005; Weigl, 2005; Wilkins, 1989; de Magalhaes and Costa, 2009)
Brazilian free-tailed bats are social animals that live in large groups called colonies that call, squeak, and move around. They start searching for food right after sunset and keep going throughout the night. They may fly 50 km or father to get to a feeding area. They fly quickly in a straight line. They fly at a higher altitude than other kind of bats, going up to 3300 m. They can fly a long ways, which means they can find food in a large area and travel between summer and winter locations. The most active they get during the day is feeding and searching for places to rest, which happens in the late morning and afternoon during the summer and early fall. They are more active in warm weather. (Allen, et al., 2009; Svoboda and Choate, 1987; Williams, et al., 1973)
Brazilian bats can search for food in an area up to 400 square km. In just one night, they might travel 25 km searching for food, or even as many as 65 km. (Williams, et al., 1973)
Brazilian free-tailed bats navigate and find prey by echolocation, which is a way of judging distance by listening to echoes. While flying, they send out calls with constant frequency. When they pick up on food or another object, their calls change frequency to between 75 and 40 kHz. Their normal frequency is 49 to 70 kHz, but can drop to 25 to 40 kHz when objects cross their flying path. Brazilian free-tailed bats recognize each other using echolocation and also chemical signals, sight, and hearing. Females find their young by scent and recognizing the sounds they make. (Gannon, et al., 2005; Gillam and McCracken, 2007)
Brazilian free-tailed bats eat insects out of the air while they are still flying. They eat different things in different areas, but mostly eat moths, beetles, dragonflies, flies, true bugs, and wasps, bees, and ants. What they eat depends on what is available, the weather, their body's energy use. How bright the moon is can also affect which insects are available to eat. (McWilliams, 2005)
Brazilian free-tailed bats are eaten by birds of prey like red-tailed hawks, American kestrels, great horned owls, barn owls, and Mississippi kites. Virginia opossums, striped skunks, and raccoons are all mammals that eat them when they are resting. They are also eaten by snakes like eastern coachwhips and eastern coral snakes. Despite all these predators, not very many Brazilian free-tailed bats end up being eaten compared to how many there are. ("Brazilian Free-tailed Bat", 1997; Davis, et al., 1962)
Brazilian free-tailed bats are also known as guano bats. Guano is the name for the body waste that builds up on the ground, and can be used for fertilizer. It also can transmit diseases, and increase parasites during warm summer months. The bats are more likely to get parasites if they live in a colony. They get mites, ticks, chiggers, fleas, and beetles. These parasites can transmit other diseases, too. Some chiggers infect their nose, and others get in their blood or digestive system. Like other mammals, Brazilian free-tailed bats carry rabies and five other viruses. These are: Rio Bravo virus, St. Louis encephalitis virus, Eastern equine encephalitis, Western equine encephalitis, and Japanese B encephalitis. (Davis and Loomis, 1971; Davis, et al., 1962; Jameson, 1959; Wilkins, 1989)
Brazilian free-tailed bats decrease the number of insects during the summer. Their resting locations are sometimes used by deer mice or squirrels. They also share resting spots with cave myotis, and can even be found inside one another's colonies if it gets crowded. They fly on different paths out of the cave, so they don't get in each other's way. (Davis and Loomis, 1971; Davis, et al., 1962; Jameson, 1959; Wilkins, 1989)
Brazilian free-tailed bats aren't known to have a negative impact on humans. On the other hand, their guano might transmit the disease histoplasmosis. They can also carry rabies, which is deadly to humans. (Gannon, et al., 2005)
Brazilian free-tailed bats eat lots of insects every night, including some that are pests to farmers or others that carry disease. The build-up from their body waste, called guano, is used as fertilizer and also used in gunpowder. (Clark Jr., et al., 1996; Davis, et al., 1962)
The number of Brazilian free-tailed bats has decreased in the past 100 years. This might be from disturbing their daytime locations or from being poisoned by pesticides. Brazilian free-tailed bats are listed as "Near Threatened" by the IUCN Red List. They have created a species action plan for conservation. (Arita, 1993; Gannon, et al., 2005)
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