Mammals

The feet of mammals vary greatly, largely according to how much they climb, walk, or run. Bears and monkeys stand on the whole foot, from the toes to the heel. Members of the dog and cat families stand and run only on their toes. The foot is greatly elongated, so that the heel appears to come a long way up the leg. All these animals have five toes. But in the last adaptation the number of toes decreases.

The ungulates, such as antelopes, pigs, horses, and cows, stand right on the tips of their toes, and often do not have all five. For example, the rhinoceros has three toes, the camel two, and the horse only one. The nail on the horse's single toe has become greatly enlarged to form a hoof. The cloven hoof of pigs and cattle is really two separate toes. The ungulates include all the mammals with horns; they are all plant-eaters.

When Captain James Cook was exploring the coast of Australia in 1770 he saw a strange sight-'an animal as large as a greyhound, of a mouse colour which went only upon two legs, making vast bounds, just as the jerboa does'. It was the first kangaroo seen by Europeans!

A marsupial is an animal with a marsupium-that is a pouch in which the mother can carry her young. Marsupials were common in many parts of the world about 100 million years ago, when dinosaurs were still roaming the Earth. But they died out everywhere except Australia, New Guinea and some neighbouring islands, and in South America.

The, reason? Australia, New Guinea, and South America were isolated from the rest of the world for millions of years. More advan­ced animals did not develop to compete with marsupials. Eventually, South America joined up with North America, and one species of the South American marsupials moved north. Americans call these marsupials possums.

Ordinary mammals produce fully developed young, even though they are small and helpless. But marsupial babies are minute and only partly formed. They have just enough strength for the most difficult jour­ney they will ever make-over their mother's abdomen and into her pouch. There they stay, suckling on teats, until they are big enough to venture into the world outside.

Most marsupials have their pouches opening forward. Some which dig burrows or live in dense vegetation have the pouches opening backwards so that the soil and other rubbish will not get in.

There are about 250 species of marsupials. Many of them are the equivalents of ordinary mammals in other parts of the world. For example, there are marsupials similar to dogs, cats, mice, rats, moles, badgers, and squirrels-but they have evolved quite independently! But there are animals that are quite different, such as the kangaroos.

A Red kangaroo stands about 5 feet (1.5 m) tall, but its baby at birth measures on1y 1 inch (2 cm) long.

A bandicoot is a little marsupial that looks a bit like a cross between a rat and a kangaroo. It hunts through the undergrowth for insects and worms, and makes a noise like a squeak with a sneeze in it. There are 20 species of bandicoots, and they are between 15 inches and 30 inches (38 cm-76 cm) long.

Wombats are sometimes called 'badgers' because they are something like a badger in shape and size. Some people call them living bulldozers. These chunky animals, up to 3 feet (1 m) long, dig huge burrows with a maze of tunnels. They like to live on their own.

Wallabies are cousins of the kangaroos. They are smaller, the biggest being only half as large as a kangaroo. The Nail-tailed wallaby swings its arms round like windmills when it is bounding along, and has a nail-like tip to its tail. Tree kangaroos are small wallabies that climb trees. They live in the forests of New Guinea and northern Queensland.

Kangaroos are the best-known of the marsupials. They have only one young at a time. But soon after giving birth a mother kan­garoo conceives again. The new baby develops a little way and then stops. It is kept in reserve, and as soon as the first 'joey' becomes independent or dies development starts again.

When explorers from Australia brought the first skins of the Duck-billed platypus back to Europe, zoologists just could not believe their eyes. They thought a mammal with a beak like a duck must be a fake. And when people reported that these strange beasts laid eggs -that was too much! But it is true. The platypus is one of a group of animals called monotremes, because they have only one opening-a monotreme-at the end of their digestive and reproductive systems, like birds and reptiles. But they have mammary glands and suckle their young once they are hatched.

There are three kinds of monotremes. The platypus lives in Tasmania and south-eastern Australia. The Spiny anteater is found in Australia and New Guinea. The Long-beaked echidna, another anteater, lives only in New Guinea.

The simplest of the true mammals, those with placentas which give birth to live young, are the insect-eaters, a small order (Insectivora) of little animals. They include shrews, hedge­hogs, and tenrecs.

Hedgehogs (family Erinaceidae), are animals with a forest of prickly spines all over their backs and sides. Muscles enable the hedgehog to erect its spines for defence.

True shrews (family Soricidae) are small animals which work and rest on a three-hour shift pattern, day and night. Their unpleasant odour keeps them safe from most predators.

Tenrecs (family Tenrecidae) live on the island of Madagascar, and some have been taken to Reunion and Mauritius.

Otter shrews (family Potamogalidae) live in Africa. They swim like otters, feeding on fish.

Elephant shrews (family Macroscelididae) are also called Jumping shrews, because they jump like jerboas. But they have long, trunk-like snouts. They live in Africa.

Moles (family Talpidae) are the master burrowers of the insectivores. A mole can dig its way through 45 feet (14 m) of soil in an hour-and in the mating season it can dig through 150 feet (36 m)! Moles' eyes are cap­able only of distinguishing light and dark.

Golden moles (family Chrysochloridae) are related to ordinary moles, but their fur is a coppery colour instead of the dense black of their cousins. They live in Africa.

Desmans are somewhat like moles, but lead an aquatic life, burrowing into river banks.

Hedgehogs (Erinaceidae) hide by day in thickets, tree stumps, or rocky hollows, emerging at night to snuffle around looking for their food. When attacked, they erect their prickles and roll into a ball. Any attempt to prise the hedgehog open merely makes it roll up even more tightly. Only the fox and badger can beat this defence, by rolling the prickly ball into a pond or puddle. The hedgehog at once unrolls in order to swim, and can easily be killed.

Another defence mechanism is that hedgehogs are largely proof against snake-bite. The European hedgehog (Erinaceus europaeus) is known to kill and eat small snakes-and it also varies its insect diet with mice, frogs, birds' eggs, and carrion.

Bats are the only mammals that have mastered the art of flying, though several other species, such as Flying squirrels, Flying lemurs, and Flying phalangers, have managed to become successful gliders. The bats form the order Chiroptera, which means 'hand-wings'. And that is literally what bats have-hands whose fingers have become greatly lengthened, and are connected by a thin membrane of skin to provide a wing surface. The thumb forms no part of the wing, but can be used for holding on to things. The membranes extend from the 'hands' down the sides of the bat's body until they reach the hind limbs, and there is a further stretch of membrane joining the back legs and the tail. Long hooked claws on the back feet enable the bat not only to climb but to hang from a branch or ledge even while asleep.

A female bat has one young at a time. The baby rides everywhere with her for a while, but then remains on the roost until it is able to fly.

There are two main kinds of bats. Fruit bats form the suborder Megachiroptera, and all the largest kinds of bats are in this group. The insect-eating bats (Microchiroptera) are generally much smaller. The bats rest by day and come out to feed at night. They use a form of sonar to navigate and the insect-eaters also use it to locate their prey. There are more than 750 species of bats. They are grouped in 17 families, one of which includes all the fruit bats.

Bats of all families have a sonar system built into their brains. When it is flying, a bat emits a rapid series of ultrasonic (above human hearing) signals, which bounce off any object in its path. The echo is detected within one-thousandth of a second, thus enabling the bat to take avoiding action even at the last moment. Bats can fly through a maze of wires without touching one, even in the dark.

Bats emit their signals in two different ways. Some send them out through the mouth, and those that do generally have long snouts. Others send the signal through their nostrils, and they have leaf-like projections above the nose. The nose-leaves serve both to focus the signals, and to prevent them from striking the bat's own ears directly. These ears, which receive the signals, are large and mobile.

Bats find their prey, such as moths, with the aid of the sonar. But many moths are sensitive to the signals, and can take swift avoiding action. Even then, the bat sonar is so efficient that it can make a last-minute swerve to intercept a moth that has changed course. Some moths themselves emit signals which 'jam' the sonar-but bats do not interfere with one another's signals, even when thousands are flying at the same time.

The insect-eating bats (suborder Microchiroptera) form the largest part of the bat world, and three out of the 17 families are really widespread. Nearly all of them hunt on the wing, using sonar. Although called insect-eaters, some eat spiders, fruit, frogs, or fish -and a few prey on small birds and other bats. They live in dark places such as caves, and hollow trees.

The Vesper bats (family Vespertilionidae) are the largest and most widely distributed of the bats. Members of this family are the most numerous bats in North America and western Europe, and there are 275 species. The largest European bat is the Great bat or noctule (Nyctalus noctula), with a wingspan of up to 15 inches (38 cm).

False vampires (family Megadermatidae) are often mistaken for vampires-but they do not suck blood! They are found in Africa, Asia, and Australia, and some of them are very large. The Indian false vampire (Megaderma lyra), eats flesh, including other mammals, birds, frogs, and lizards. Several American species of the family Phyllostomatidae, the Leaf-nosed bats, are also called 'vampires', though some of them prefer the nectar of flowers!

The Jamaican flower-bat (Phyllonycteris) and the Long-nosed bat (Leptonycteris nivalis) not only drink nectar but pollinate the flowers, doing the work of bees.

Vampires, according to eastern European legend, are the ghosts of evil men who return in bat-like shape to drink people's blood; Which is why, when real blood-sucking bats were found in' tropical America, they were called vampires. They form the family Desmodontidae, and there are three genera, Desmodus, Diphylla, and Diaemus. They are night-prowlers, seeking sleeping victims for their sole source of nourishment-blood. The Great vampire bat (Desmodus rotundus), which weighs about 1 oz (28 g), drinks a tablespoonful of blood every day, from large mammals such as cattle. The smaller vampires suck from large birds.