A Kangaroo is a marsupial. That means that it's offspring is naturally born underdeveloped and it has to carry it inside a pouch flapped in front of it until the offspring is fully developed and capable of natural activities by itself.
Kangaroos and Self Defense
kangaroos have powerful feet. Feet capable of breaking your rib cage in one blow and puncturing your organs. When a kangaroo fights, it lifts itself up on it's hind legs, most time the tail is helped to sustain balance. It then jumps and thrust it's powerful feet at it's opponent. It does more of a kick boxing that hand boxing. The hands do come in handy as it can be used to hold sown certain animals in order for it to thrust it's powerful legs at them. They do use the hands to thrust at their opponents also, but most of the damage comes from the Kangaroos powerful feet.
This is where they image comes from that kangaroos love to box, but it is just the way they fight which makes it seems like boxing. But kangaroos don't just go picking fights in the street. They would prefer to roam around in the outbacks grazing all day.