Bats' wings have evolved over long period of time

By Jim Hurley - Nature Trail

Published 09/06/2015 | 00:00

A bat's wing is a truly amazing product of evolution.
A bat's wing is a truly amazing product of evolution.

A bat's wing is a most remarkable structure and a truly amazing product of evolution.

Bats are the only mammals in the world that are capable of true powered flight and they all share a common wing structure. Fossil bats dated to over 50 million years ago have been found evidencing that their wings have evolved over a very long period of time.

A bat's wing is its arm and while the wing may appear to be very different from our own arms we do share a common arrangements of bones.

The membrane of the bat's wing is made of skin. The skin is very thin, elastic, finely stretched and often covered with very fine, short hair. It is prone to getting torn easily.

When a bat snatches an insect from vegetation and flaps to take off it may inadvertently tear its wing membrane on a briar.

A torn wing is of little value for flight so bats have amazingly rapid healing. How the torn skin repairs itself so quickly is obviously a matter of great interest to medical scientists.

A bat's wing is its arm. The skin of the membrane stretches from the bat's shoulder to its wrist with its upper arm, forearm and elbow joint all fully enclosed in the membrane.

Its arm bones are extremely thin and long. Its thumb is free and is usually equipped with a substantial claw that the bat uses for climbing, fighting, hanging on to rough surfaces, etc.

The remaining four fingers of the hand are exceptionally long and skinny and the web is stretched between them. The index finger forms the leading edge of the wing. The middle finger extends to the outer extremity of the wing tip and the ring finger and little finger support the middle part of the wing.

The tips of the fingers are flexible allowing the trailing edge of the membrane to be raised or lowered thereby changing the shape of the wing to produce an aerodynamic force.

From the tip of the little finger, pinkie or fifth digit the skin of the wing stretches to the ankle and on to the tail to complete the amazing structure. The bat's foot is entirely free and is equipped with five long toes.

Ten species of bat have been recorded in Ireland. Leisler's Bat is the largest with a wing span around 300mm and the Common Pipistrelle is the smallest with a wing span around 200mm.

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