A kangaroo is any of several large macropods (the marsupial family that also includes the wallabies, tree-kangaroos, wallaroos, pademelons and the Quokka: 63 species in all). The term kangaroo is sometimes used in a broader sense to refer to all members of the macropod family. Kangaroos are endemic to the continent of Australia, while tree-kangaroos are found on both Australia and New Guinea.
Kangaroos have long been regarded as strange animals. Kangaroos have large, powerful hind legs, and large feet adapted for leaping. They have a long muscular tail for balance, and a small head. Like all marsupials, kangaroos have a pouch called a marsupium in which their young complete their development after birth.
Kangaroos are the only large animals to use hopping as a means motion. The comfortable hopping speed for Red Kangaroos is about 13 to 16 mph (20″“25 km/h), but they can hop as fast as 43 mph (70 km/h) over short distances. They have to hop fast because less of the need to regularly cover large distances in search of food and water.
Unlike that of many other mammals, a kangaroo’s scrotum (which the males have in place of a pouch) is located far ahead of the penis. The average life expectancy of a kangaroo is about 9 to 8 years, with some living until they are about 28.
Kangaroos are large herbivores, feeding on grass and roots, and they chew cud. All species are nocturnal and crepuscular, usually spending the days idling quietly and the cool evenings. The nights and mornings they move about and feeding, typically in mobs.
Kangaroos have few natural predators. Along with dingoes and other canids, species like foxes and feral cats can pose a threat to kangaroo populations. Kangaroos and wallabies are apt swimmers, and often flee into waterways if presented with the option. If pursued into the water, a large kangaroo may use its forepaws to hold the predator underwater to drown it. Another defensive tactic described by witnesses is catching the attacking dog with the forepaws and disemboweling it with the hind legs.
Social life and courtship
A mob may have ten or more males and females. The dominant male (called a boomer) is based on his size and age. A boomer has temporary exclusive access to females in a mob for mating. He may find himself wandering in and out of a mob. They check out the females and intimidate the other males who try to mate with the females within the mob.
Courtship behavior in most species of kangaroos includes the male “checking” the female’s cloaca. The male often rejected by the female for their smaller size. In the case of a larger kangaroo, the female may instead simply move away. Often, when the female is being checked, it urinates. The male kangaroo will sniff the urine multiple times until it is satisfied, then proceed to the mating cycle. The sexually aroused male follows the responsive female (she raises her tail). Tail scratching (a form of foreplay) can occur between the male and female. The arched tail is indicative that either one or both kangaroos are ready to mate. The male kangaroo may sometimes be found giving the female kangaroo a back rub before mating.
Kangaroos have developed a number of adaptations to a dry, infertile continent and a highly variable climate. As with all marsupials, the young are born at a very early stage of development after a gestation of 31-36 days. Only the forelimbs are somewhat developed, to allow the newborn to climb to the pouch and attach to a teat. The joey will usually stay in the pouch for about 9 months or (for the Western Grey) 180 to 320 days. Then they start to leave the pouch for small periods of time. The joey is fed until 18 months of age.
A female Kangaroo has the ability to freeze the development of an embryo until the previous joey is able to leave the pouch. This is known as diapause and will occur in times of drought and poor food sources. The composition of the milk produced by the mother varies according to the needs of the joey. The mother is able to produce two different kinds of milk simultaneously for the newborn and the older joey who still lives in the pouch.
Kangaroos and wallabies have large, stretchy tendons in their hind legs. They have evolved for leaping. They store elastic strain energy in the tendons of their large hind legs. This provides most of the energy required for each hop by the spring action of the tendons rather than by muscular effort.
There is also a linkage between the hopping action and breathing. The feet leave the ground; air is expelled from the lungs; bringing the feet forward ready for landing fills the lungs again. This action provides further energy efficiency. Studies of kangaroos and wallabies have demonstrated that, beyond the minimum energy expenditure required to hop at all, increased speed requires very little extra effort. Little extra energy is required to carry extra weight. The top speed of a kangaroo is no higher than that of a similarly sized quadruped. The ability of a kangaroo to travel long distances at moderately high speed in search of fresh pastures is crucial.