The kangaroo lives in groups of up to 15. The males compete for females during the breeding season. During these "boxing" contests, they would lock arms and try to push each other over. Usually, only the strongest male in the group mates. The gestation period is 30–31 days. After the birth, the tiny baby Joey attaches to the teat in the females pouch for nine months. After it comes out of the pouch, it will continue to drink milk from the mother's pouch for about another nine months.