The male killer whale has a sword-like dorsal fin which stands 2m straight out of the water. The female's is shorter, and slopes backwards. The female can reach sexual maturity between 8 and 14, but males take longer to mature, taking on average about two years longer. It is likely that there is some sort of courtship, and single males probably breed with several females. Females give birth to a single calf after a gestation period of twelve months. Even at birth, the calf is 2m long, almost a third of the size of its mother! The calf stays with its mother for several years, and suckles for the first year of its life. The female is fully occupied with the new calf, and so may not breed again for 3-8 years.