Flying without wings

You may be familiar with birds that fly, but squirrels, lizards, frogs, snakes or for that matter fish? Perhaps not. Some of you may wonder whether such 'flying' animals could only be found in story books or movies.

No, they do exist in the real world, if only you take time to learn about the numerous creatures that exist in the animal kingdom. However, keep in mind that these animals, which are known as the flying squirrels, flying snakes, flying fish and so on, do not actually fly like our feathered friends - the birds, because they have no wings. Neither do they use wind currents to soar up in the skies like birds do, but they do move freely in the air for quite long distances, to get from one point to another.

This unusual mode of transport of moving through the air without wings is called gliding. So, why are these animals called flying squirrels or flying fish, you may question. Well, because even though they have no powered flight like the birds, their gliding methods look so close to flying. And, naturally they have come to be classed as a group of animals that could 'fly'.

Now, let's look at how exactly each of these animals manage to fly even though none of them have wings.

Fish that fly

There are over 50 species of flying fishes belonging to the family Exocoetidae. They are mostly marine fishes of small to medium size, with the largest among them reaching a length of 45 cm. Most species measure less than 30 cm in length.

Flying fish can easily be identified by their huge flying fins and lopsided tails. Young fish look quite different from adults. They have variegated colour patterns (diversity by patches of different colours), and a pair of flap-like whiskers that extend downward from the end of the lower jaw and are sometimes longer than the fish itself. These whiskers disappear as the fish grows.

These flying fish are capable of jumping out of the water and gliding over considerable distances. There are two-winged flying fish with exceptionally large pectoral fins, and four-winged flying fish, which also have enlarged pelvic fins used for gliding.

In general, their tails are deeply forked, and the lower lobe of the tail is much longer and larger than the upper lobe. When these fish want to escape from hungry predators such as starfish, they take to the air. They leap out of the water, up to about 2m (6 feet) and then glide along with outstretched fins. In preparation for flight, they quickly swim towards the water's surface, leap out of the water and spread their chest fins like wings, keeping them airborne for up to 100 m (325 feet).

Studies have revealed that flying fish hold their enlarged pectoral fins relatively steady and glide through the air, like the lizards, squirrels and snakes that fly. Birds vibrate their wings during flight, but these flying fish don't.

Even lizards take to the air

Like the squirrels, these small lizards 'fly' or glide hundreds of feet from tree to tree. They do so using the extra skin flaps they have between their front and hind limbs. They have long ribs, some of which fold back against the sides of their bodies, that they extend when leaping from tree to tree.

When these lizards spread their ribs, opening umbrella-like fans of skin, and leap from a tree and glide, sometimes up to about 20 m (60 feet), they truly look as if they are flying.

Some species of lizards are considered to be champion gliders.

Squirrels can also fly

You may be aware that squirrels are mammals and belong to the order of 'gnawing mammals' (Rodentia). The name 'squirrel' comes from the Middle English word 'Squirrel', which in turn comes from the Greek word 'Skiouros'. The flying squirrels are scientifically known as Petauristinae or Pteromyinae. There are about 36 species in this sub-family of squirrels and the largest among them is considered to be the Woolly Flying Squirrel.

Found mostly in tropical forests in different locations (according to the species), such as the Ivory Coast, Liberia, Guinea, and North America, these squirrels generally have dense, bristly coats. The squirrel identified as Pel's Flying Squirrel is said to be black on top with a white underside. Its body is around 18 inches long, with an additional 14 inch long tail which it uses effectively when flying. It weighs just under two pounds.

There are two sub-species of flying squirrels which are native to North America, which are grouped as the Northern and Southern flying squirrels.

What helps them fly?

A fold of skin from the front limbs which is attached to the hind legs, and the base of the tail, near where it joins the body helps these rodents to fly.

These loose folds of skin between the front and hind legs on either side stretch and act as 'wings' when they extend their limbs. Once they have launched themselves into the air, they have no way of propelling themselves forward, like birds do, by flapping their wings. They simply glide, even though they lose height while doing so. The squirrels can steer themselves or control direction by tensing and turning their legs and body, and also flapping their tail.

The tail acts as a stabiliser in flight, very much like the tail of a kite. They can turn easily at right angles while gliding as far as 150 feet or more from a height of 60 feet! As they approach landing, the squirrels flip the tail up and hold their body back to slow the glide down. This gives them ample time to position their feet for grasping the tree trunks. As the squirrels have sharp, long claws, they can easily grasp the tree trunks. They usually land face up.

In the wilds, they live only for about five years, but in captivity they often live up to 10 and 15 years.

Fact file

* They eat berries, blossoms, acorns, seeds and fruit which are all found on trees, where they usually take refuge, and also moths, insects, birdlings and eggs.

* They glide from tree to tree, covering distances up to 165 feet.

* Their enemies include snakes, racoons, nocturnal owls, coyote and the domestic house cat.

* They are sociable animals with strong maternal instincts.

* Some species are known to make affectionate and playful pets.

* Flying squirrels are active all year round.

More on flying animals next week.