Page 144 - Present Day Wildlife_Float

The term rodent (L. to gnaw) is used to describe any one of more than 2,o5o extant species con-
sisting of 518 genera in 29 families belonging to the order Rodentia (see: Standard classification).
They all have one thing in common; upper and lower pairs of ever-growing rootless incisor teeth. They
make up 40% of all mammals and are found on every continent except Antarctica and some remote
oceanic islands. Their size varies, from the smallest, Delany’s swamp mouse of Africa, which is 5 to 6
cm long and weighs around 5 to 7 grams, to the largest, Capybara of Central and South America, that
has a length of 100 to 135 cm, stands 50 to 60 cm at the shoulder, and weighs around 35 to 66 kg.

In many ways rodents share cer-
tain physical similarities. Most are
small, with long rear limbs, with three
to five toes and shorter forelimbs, with
digits including a thumb allowing
them to hold and gnaw food while sit-
ting in a squatting position. Most have
claw-like nails, with those that burrow
having longer and stronger nails, and
tree dwellers having shorter but
sharper nails. They all have an excel-
lent sense of smell, good hearing, and
vision, with some nocturnal species
having large eyes, thought to be sensi-
tive to ultraviolet light. Nearly all
have long tails and many have long
stiff whiskers, sensitive to touch. All
rodents must be constantly gnawing at something to keep their relent-
lessly growing incisors from becoming dangerously long. There are
many different species of rodent, the most popular being, mice, rats,
squirrels, prairie dogs, porcupines, beavers, guinea pigs, and ham-
sters. Rabbits were once thought to be rodents, but along with hares,
and Pikas were placed in the order Lagomorpha when it was discov-
ered they had two pairs of upper incisors instead of one and a slightly
different digestive system. Though they are still considered close rela-
tives of rodents.

Rodents are found in almost every terrestrial habitat across the
globe, from the Lemming living in cold snowy tundra through to the
Kangaroo rat who resides in hot and arid desert wastelands. Many live
in burrows, others in tree holes, rock crevices or nests on the forest
floor while others like beavers build complex aquatic structures. Some,
like rats and mice, live among humans on their farms and in their
towns and cities. Most rodents are herbivorous, feeding exclusively on
plant material such as seeds, stems, leaves, flowers, and roots, while
some like the grasshopper mouse are omnivores, and a few, like the
Tweezer-beaked rats are carnivores. Although most rodents are classified as diurnal or nocturnal,
most do not hibernate, and need to find and store food for winter, so all rodents will hunt both day
and night if food is scarce. Only a few hibernate throughout the winter like the Groundhog, others like
the Prairie Dog and Meadow Jumping Mouse hibernate, but will awaken if it gets warm or they are
thirsty. Rodents are usually very sociable animals; some regularly congregate in groups while others
are solitary and only come together to mate. They are preyed on by many large
land predators, predator birds and domestic cats and dogs.