|From the super swift cheetah to the ponderously
slow sloth, different mammals move in their own distinctive ways. The design
of an animals body determines its characteristic way of moving. Movement is
essential to an animals survival, enabling it to search for food and to escape
from enemies. Mammals are among the animal worlds most versatile movers,
with species adapted to a full range of motion, from swimming through water
to gliding or flying through the air.
Limb Movements: Most mammals walk using the same limb movement as a crawling baby. First the right forelimb is raised, then the left hind leg, next the left forelimb, and finally the right hind leg. In this way the animal is supported by three limbs and can stop short without falling. When trotting, one limb is lifted before the previous one touches the ground, leaving a moment when only the two feet diagonally opposite each other are on the ground. The animal stays stable by replacing its feet rapidly.
A few mammals, such as the horse, can sustain swift movement like galloping when only one foot is on the ground at any time and when all feet are in midair at given moments. The horses movement stems from its legs, and its back muscles play little part. The cheetah arches and stretches its flexible spine so its hind legs land in front of its forelimbs, increasing the force and length of its stride. In this way it reaches speeds of over 60 miles an hour for fairly short distances. The hanging sloth is the slowest moving mammal, and the cheetah is the fastest. The giraffe, like most four legged mammals, uses the diagonal limb sequence to walk.
Swimming: Aquatic mammals like whales, dolphins, and porpoises swim as skillfully as fish. The bottle nose dolphin, for example, has a streamlined body that enables it to move underwater at almost 20 miles per hour. It uses its muscular tail as a propeller and its fin shaped front flippers for steering and balance. By leaping out of the water as it surfaces to breathe, the dolphin avoids turbulence and maintains its speed.
Semi aquatic otters move easily in water. Using their backs and tails when swimming, they can reach speeds of 15 miles an hour. But otters usually paddle underwater by using hind leg movements, interspersed with bursts of fast swimming and gliding. To see and breathe, they raise their heads and chests above the surface while treading water. They also float stomach down, with their eyes, ears, and nostrils above water. On land, otters move awkwardly, with neck and head held low, hips and lower back arched, and muscular tail extended behind. Otters are more agile in water than on land.
Jumping, Climbing and Swinging: The kangaroo moves by hopping and jumping, using its long, thick tail as a support and a counterweight. Like other leaping mammals such as the jerboa and kangaroo rat, it propels itself with its large hind legs. The kangaroo can travel up to 30 feet in one bound, keeping its tail raised for balance. When it hops, its bent tail acts as a third leg. Climbing and leaping are movements characteristic of leaf eating monkeys like the colobus and proboscis. These mammals use their hind legs to propel themselves into a leap, and they grasp vegetation with their forelimbs as they land on their hind legs. Moving along a branch they use their hands and feet in the diagonal limb sequence.
The gibbon grasps branches with alternate hands, hurling itself along with each grasp. Its long arms and mobile wrists and shoulders even let it cross gaps between trees. South American monkeys and most tree climbing marsupials have a prehensile (gripping) tail, which they can wrap around branches, leaving the body suspended while feeding.
Mammals in Flight: The bat is the only mammal that uses true flight to move. Its body is designed for flying. The skeleton is delicate, but the forelimbs are well developed, with powerful shoulder joints to bear the weight of the body. The long forearm is webbed by a thin double layer of skin that forms the wing membrane and the bats flying mechanism. With the wing membrane extended, the bat flies just like a bird, using a series of beating wing movements. But since it can use tendons in its arm muscles to flex all its joints, the bat has perfect control of its wings and is better able to maneuver in flight than other flying creatures. When the bat is not in flight, its wings can be folded over so they do not interfere with walking. The bats hind legs are also used in flight. When they are extended the bat can kick downward, adding power to its wing beat. The arrangement of bones and tendons in the bats leg allows it to rest hanging upside down by its claws.
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