Bats: Chiroptera

Bats are the second largest group of mammals after rodents. Almost one out of every four mammalian species on the planet is a bat species. Living bats are categorized into two main groups, each with its own distinct features. The Megachiroptera (mega-keer-OP-ter-ah), or "large bats" group includes one family. The Microchiroptera (micro-keer-OP-ter-ah), or "small bats" group includes all the rest of the bats.

Bats are the only mammals that can fly. Chiroptera comes from the Greek roots cheiro (hand) and ptera (wing), named for the similarity of a bat wing to a hand. Bat wings are long arms, hands and extra-long finger bones that are covered with a double layer of thin skin called a membrane. The membrane is thin enough that light can shine through it. The membrane contains blood vessels, nerves, and muscles.

In some bats, a membrane extends between the legs and encloses the tail. Some bats have tails that extend past the membrane and others have no tails. In most bats, the thumbs are free from the membrane. These thumbs have claws and are often used for climbing up trees or other structures.

Bat membranes are tough and flexible, allowing bats to move their wings much like people move their fingers. Changing the shape of their wings allows bats to turn and maneuver quickly. Some bats can hover in the air while others glide. When it is cold, the bats fold their wings around themselves. When it is warm, bats flap their wings to cool themselves.

Bats range widely in size, yet the majority of bats weigh less than 1 ounce (25 grams). The largest bat is the Malayan flying fox, which can have a wingspan of 6 feet (1.8 meters) and weigh 3.3 pounds (1.5 kilograms). The smallest bats are the Kitti's hog-nosed bats, also called bumblebee bats, of Thailand, with a wingspan of 6 inches (15 centimeters) and a weight of about 0.07 ounces (2 grams), less than a penny.

Like other mammals, bats are warm-blooded and fur covers their body. Megachiroptera are characterized by large eyes, small ears, and dog-like snouts. Most Microchiroptera species are characterized by wide, extended ears and odd shaped noses. Bats have weak legs and do not walk long distances. Their feet are small with sharp claws on each toe. Bats use their claws to hold the weight of their body when they hang upside down, which is their normal resting position.