Sheath-Tailed Bats Sac-Winged Bats and Ghost Bats: Emballonuridae

Emballonurids (bats in the family Emballonuridae) are small to medium in size. Their head and body length is about 1.4 to 6.3 inches (36 to 160 millimeters). They can weigh from 0.1 to 3.5 ounces (3 to 100 grams), about the weight of a first-class letter. These bats have thirty to thirty-four teeth.

For the most part, emballonurids are brown or gray in color, but this family also includes the whitish ghost bats in the genus Diclidurus, and bats with a pair of white stripes down their back in the genus Saccopteryx. Emballonurids have a smooth face and lips with relatively large eyes. Their ears are usually round and cup-shaped, often joined by a band of skin across the forehead. The ears have a tragus (TRAY-gus), a flap that projects from the inner ear. Researchers theorize the tragus plays some role in echolocation (eck-oh-loh-KAY-shun), the process of sending out high-pitched sounds and identifying objects by interpreting the sound when it bounces back.

Some emballonurids are also known as sheath-tailed bats because of their tail. They have a short tail that juts out from the membrane (double layer of thin skin) between their legs, and when their legs are stretched out their tail appears to be sheathed in the membrane. Another name for some emballonurids is sac-winged bats, referring to the glandular sacs in their wing membranes. Glandular sacs produce and release substances for use in the body. In this case they contain a liquid with a strong odor. In the sac-winged bats these sacs are more pronounced in males. The position and size of these sacs differs depending upon the species.