DISK-WINGED BATS – Thyropteridae

DISK-WINGED BATS

BATS FACTS

These bats are about the size of a person’s thumb, having a head and body length that ranges from 1.2 to 2.3 inches (3 to 5.7 centimeters). They weigh from 0.10 to 0.17 ounces (3 to 5 grams), about the same weight as one to two pennies.

These bats are also called New World sucker-footed bats, named after the suction cup-like feature found on their feet. These bats have circular suction cup disks with short stalks on the soles of the feet and the bottom of their thumbs. The disks on the thumb are larger than those on the feet. They also have a well-developed claw on their thumb.

Bats in this family have small eyes. There is a small wart-like projection above the nostrils, and there is no noseleaf (leafshaped fleshy protrusion). The tail juts out freely past the membrane (thin layer of skin), so it is visible. The ears are large and shaped like a funnel. The muzzle is long and slender. Nostrils are circular and set relatively far apart.

Species in this family have long, fluffy hair. Fur color ranges from a medium reddish brown to slightly darker. The undersides of these bats are white or brown. The ears can be either black or yellow.

GEOGRAPHIC RANGE

These bats are found in Central and South America, east of the Andes, including southern Nicaragua to the Guianas and Peru, and southern Mexico to Bolivia and southern Brazil, and Trinidad.

WHERE DO BATS LIVE

Disk-winged bats live in the moist parts of forests. They are common in many areas, and in Costa Rica there are up to four colonies (groups) for every 2.5 acres (1 hectare). They generally roost (rest or settle) in a curled leaf of some plant, such as the heliconia plant or the banana tree, before the leaf opens.

WHAT DO BATS EAT

Disk-winged bats eat insects.

BEHAVIOR AND REPRODUCTION

Disk-winged bats use only their suction-like disks to grip and stick to the smooth surfaces of the curled-up leaves in which they roost. They do not use their feet or claws to touch the surface of the leaves.

These bats can support their entire weight with the suction of a single disk. Sweat glands keep the disks’ undersurfaces moist, which helps provide the vacuum seal for sticking to the surface. Beneath each disk is a muscle that controls the vacuum. This muscle can create the seal and, when the bat wants to come unstuck, the muscle also undoes the seal. These bats will also lick their disks to help with the suction. Studies have found that these bats have lost the ability to roost on rough surfaces, such as trees and rocks.

Generally only one or two disk-winged bats roost in the same leaf, yet observers have found as many as eight individuals in one leaf. Roosting inside curled leaves protects them from the weather and predators. Leaves open within days, and groups must change roosts often.

Like all bats, these bats are nocturnal, meaning that they are active at night. When more than one bat roosts in a leaf, these bats spread out evenly, one above the other. In Costa Rica, a study reported that group sizes ranged from one to nine, and averaged six bats. Generally, the same group moves together from one old leaf to a new roosting site. Bats in this family have been found roosting with bats in another family, the proboscis bat.

Unlike most other bats, individuals in this family typically hang with their head upward. Disk-winged bats use echolocation (eck-oh-loh-KAY-shun) to find prey (animals hunted for food) and detect objects. Echolocation is a process for locating objects by emitting, sending out, sounds, which are reflected back to the bat by objects in the sound’s path.

Females roost together in hollow logs to give birth. Males in this family are thought to be polygynous (puh-LIJ-uh-nus), meaning they mate with more than one female during the mating season.

DISK-WINGED BATS AND PEOPLE

People have caused the decline in this family’s population due to disturbing and destroying their natural habitat. Because they feed on insects, these bats eat many insects that people may consider pests.

CONSERVATION STATUS

Although these bats are common in some areas, the IUCN lists Thyroptera lavali as Vulnerable. In 1999, findings observed that Thyroptera lavali was restricted to a small area in extreme northeastern Peru.