Kangaroos are found in Tasmania, Australia, and New Guinea. In Australia, kangaroos fill the niche held on other continents by grass eaters such as deer, zebra, antelope, and bison. Different members of the family, known as Macropus giganteus, can be as small as a rat or as big as a man. The man-sized kangaroos of Australia can reach speeds of up to 55 mph for short distances, as their powerful hind legs carry them over the ground in jumps of 30 teet or more at a time. These impressive legs are also the kangaroo's primary means of defense. A threatened kangaroo may put its back to a tree and kick at an attacker with its clawed hind feet. The blows from such kicks can easily be powerful enough to kill. The kangaroo has long had a well known association with everything Australian much the same as the koala bear is.