Smithsonian National Museum of Natural History, North American Mammals
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Balantiopteryx io

Thomas's Sac-winged Bat

Order: Chiroptera
Family: Emballonuridae


Conservation Status: Vulnerable.

The sac of a sac-winged bat is a special gland located on top of each wing. It seems to play a special role in courtship. A male interested in a female hovers in front of her with the sacs open. They emit a smell that the male hopes she will find attractive.

Thomas's Sac-winged Bat is tiny, delicate, and agile. Fifty or more of them often roost together in the dark part of a limestone cave. Because they do not leave their day-roosts to forage until after dark, it is not easy to see them flying and feeding. They eat small insects that they catch on the wing, using echolocation to find their prey.

Range: Head and Body: 38-44 mm; Tail: 8-18 mm

Range: 3-4 g


Thomas, O., 1904. Annals and Magazine of Natural History. ser. 7, 13:252.


Mammal Species of the World

Mammalian Species, American Society of Mammalogists' species account

Distribution of Balantiopteryx io