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Rodents are not just rats and mice

Posted in Animals, Nature, Wildlife on Sunday, 31 January 2016

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This edited article about rodents originally appeared in Look and Learn issue number 155 published on 2 January 1965.

coypu and water vole, picture, image, illustration

The Coypu and a water vole, large and small rodents

When we hear the word “rodent” we immediately think of rats. But the rat is only one of many different kinds of animals which zoologists class as rodents.

“Rodent” is a group name for about 2,000 species of animals distributed over nearly all parts of the world, including rats, mice and rabbits, and unfamiliar ones like the porcupines, the jerboa and the mink.

The name “rodent” comes from the Latin word rodo, meaning “I gnaw,” and it is this habit of constant gnawing that distinguishes the rodents from all other animals.

Unlike the horse and the cow, which chew their food, and the dog and tiger which tear it, rodents chop their way through their food in much the same way that a carpenter shaves off wood with a chisel.

Rodents do not have on each side of the jaw the large, fang-like teeth, called canines, of the dog and cat. Instead they have in front of the jaw powerful teeth called incisors, which are shaped like curved chisels – and are quite as sharp.

As fast as the tops are worn down by constant gnawing, they continue growing upwards from the roots.

If a rodent cannot have something to nibble at all the time, its incisors will grow to an extraordinary length.

Should an incisor break off, the one opposite to it goes on growing and eventually forms a curve round the animal’s head. The unfortunate rodent is then unable to open its mouth to eat and dies of starvation.

Sometimes when a top incisor breaks off, the bottom one will grow upwards until it pierces the animal’s skull and kills it.

It is this constant struggle to keep their incisors short and sharp that makes rodents so destructive. Most of their gnawing is not done for eating, but to prevent their teeth from growing too long and killing them.

That is why rats and mice are such destructive rodents. Their constant gnawing does far more damage to property than the cost of the food they steal to satisfy their hunger.

Incisor teeth are tremendously strong. Beavers can gnaw through the trunk of a thick tree in a few minutes, while a small rodent like the golden hamster is able to gnaw its way through a sheet of aluminium or similar metal.

In spite of their formidable teeth, most rodents are vegetarians, living mainly on roots, stems and nuts. Others like a diet of tree bark, and it is these that are so destructive to growing timber.

Although rodents are amongst the most destructive pests that attack man’s food and property, they are in general small creatures. Their power of destruction is out of all proportion to their size and they devour vast quantities of field crops and of stored food.

Others, such as rats, carry disease dangerous to man and to other animals. The Black Death, for example, was said to have been spread by them.

The biggest of rodents is the South American capybara. Rather like a large guinea pig, it is about four feet long and weighs 100 pounds. The capybara lives near rivers and is an expert swimmer.

Rodents are just as varied in their living habits as they are in appearance. Some, like the rabbit and wild hamster, dig burrows in the ground; others, such as squirrels, are arboreal, that is, they live in trees; some, like the beaver, are more at home in the water than on land; while yet others, such as the jerboa, make their home in the desert.

All species of rodents are relentlessly hunted by other animals and by birds of prey. Yet their numbers show no signs of decreasing; simply because of the enormous families they have.

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