Kangaroos and Wallabies

Kangaroos and wallabies are pouched mammals, or marsupials, of Australia and nearby islands. Kangaroos and wallabies have hind legs enlarged for leaping. Most species live on the ground, and some in trees. The name kangaroo is usually used for large species, and wallaby for smaller ones. They all belong to the family Macropodidae, meaning "big footed," and they are herbivorous, or plant-eating animals.

Kangaroos and wallabies hold the same place in the ecosystem as ruminants, such as deer. They graze and have similar mechanisms for chewing and digesting plants. Most members of the family are nocturnal, feeding at night.

The kangaroo's hand has five clawed fingers, all approximately the same length. It can be used for grasping. Red kangaroos in Australia. © Len Rue, Jr./The National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission. The hind feet are quite different, being extremely large and having only four toes. The first two are tiny and are joined together at the bone but not at the claw. These claws are useful for grooming. The third toe is huge, with a strong, sharp claw. When fighting, the animal may use this claw as a weapon. The fourth toe is again small, but not as small as the grooming toes.

Kangaroos are famous for their prodigious leaps—sometimes up to 30 ft (9.2 m) long and 6 ft (1.8 m) high by the gray kangaroo. Because the spring-like tendons in their hind legs store energy for leaps, they are sometimes called "living pogo sticks." It has been calculated that kangaroos actually use less energy hopping than a horse uses in running. When they are grazing, kangaroos tend to move in a leisurely fashion using all four feet plus the hefty tail for balance. They move the hind legs while balancing on the front legs and tail, then move the front legs while balanced on the hind legs, rather like a person walking on crutches. They often rest by reclining on their side, leaning on an elbow.

Most kangaroos are unable to walk in normal fashion, moving the hind legs at separate times. However, tree-dwelling kangaroos have the ability to move their hind legs at different times as they move among the branches.

Like all marsupials, female kangaroos have a protective flap of fur-covered skin that shields the offspring as they suckle on teats. The kangaroo's marsupium, as this pouch is called, opens toward the head. The pouch is supported by two bones, called marsupial bones, attached to the pelvis. No other mammals have these bones, but even male kangaroos do, despite the fact that they do not have pouches.

Some kangaroos live in social groups and others are solitary. In general, the larger animals and the ones that live in open grasslands are more social. Within a group, called a mob, the individuals are more safe. In a mob, the dominant male competes with the others to become the father of most of the offspring, called joeys. Because the dominant male is larger than the other males (called boomers), over many generations, through sexual selection the males have evolved to become considerably larger than the females (called does).