Brazilian Free-tailed Bat

Tadarida brasiliensis mexicana (Saussure)

Description:  The "free" tail which extends beyond the tail membrane separates this bat and the larger big free-tailed bat from all other bats in Kansas. The Brazilian free-tailed bat can be distinguished from the big free-tailed bat by its shorter ears in relation to its body size. The Brazilian free-tailed bat has dark brown fur that is short and velvety in texture. The underparts are lighter. Its lips are furrowed by vertical grooves, and the nostrils are surrounded by elevated skin. Its narrow, pointed wings permit fast flight. The toes of the hind feet have strong, recurved bristles which are used to groom the fur. There are 38 teeth. The Brazilian free-tailed bat has a strong musky odor.

Size:   Adults may attain the following dimensions: total length 90-108 mm; tail 10-40 mm; hind foot 8-11 mm; ear 13-19 mm; weight 8-14 grams.

Range and Habitat:   Kansas is at the northwestern edge of the breeding range of this species. A nursery colony has been reported in a building in Barber County, but many of these bats in Kansas are believed to be pre- or post-breeding wanderers from colonies in Oklahoma. Ability to fly long distances permits this bat extensive seasonal movements. Brazilian free-tailed bats may eventually be found in most counties of the state.

Reproduction:   A single, relatively large, young is born in late June or the first half of July after a gestation period of about 77 to 100 days. The young is left in the nursery where it is apparently fed indiscriminately, by any lactating female, in contrast to many other colonial bats. It grows rapidly and is capable of flight before it is fully grown. Breeding occurs from February to mid-April. Males become sexually mature in 18 to 22 months, while females mature in nine months.

Habitats:   The Brazilian free-tailed bat is a social and highly gregarious bat, even in flight. In other parts of its range it occurs by the millions, especially in natural caves. These large numbers of bats create great quantities of guano on cave floors, which become the lowest level of a food chain by creating nourishment for other cave inhabiting animals which spend their entire lives underground. The musky odor of these bats is intense in such caves, and can be detected some distance from the colony. Brazilian free-tailed bats emerge at early dusk, sometimes in huge swarms from their daytime roosting sites and forage in open places where they fly high and straight. The long narrow wings and compact body are specializations for rapid, long-distance flight.

RIGHT: A colony of Brazilian free-tailed bats leaving from Merrihew Cave just after sundown to forage for insects.

Photo by Stan Roth.Copyright 1999.   All rights reserved.

Food:   Moths and beetles along with other flying insects are consumed by these bats in great quantities. They will eat one-fourth their body weight in a single foraging session, and over half their weight during the night.

Remarks:   Predation on these bats is by owls, hawks,and other flesh-eating animals that search and feed in caves. As with other bats in Kansas, they are harmless to humans.

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