The largest of the kangaroos is the red kangaroo (Macropus rufus)

which lives in central Australia, the most arid part of the continent, and grazes through the night on grass and low herbaceous plants. It moves about in mobs of up to several hundred animals, led by one dominant male. Infant mortality is high in this harsh environment and there are relatively few males. Consequently, the reproductive cycle of the female allows two or three young to develop simultaneously at different stages: a fertilized egg in the womb, a suckling in the pouch and another youngster suckling from outside. The newborn joey, a naked wormlike creature quite unlike the parent and just 2cm long, claws itself out of the cloaca and makes a 15cm journey, lasting three minutes, to the pouch. There it attaches itself to a nipple and milk is pumped to it by the mother.