Although, distinguished by the same black and white colouration, adult male and female orcas are different in size and shape. Adult males may reach 9.8 metres (32 feet) and weigh as much as 10 - 11 tons (9 - 10000 kg). Most adult orcas are slightly smaller than this. Adult females may grow to 8.5 metres (28 feet) and weigh 7 -8 tons (6500 - 7500 kg), but they are also typically smaller than this maximum. Adult males have a much larger dorsal fin than the female; the male fin may grow as tall as 1.7 metres (51/2 feet) whereas the female fin may only grow as tall as 0.9 metres (3 feet) and is typically more curved than the adult male fin. It is also possible to tell male and females apart by the difference in their markings around their genital areas. At birth, newborn orcas are about 2.4 metres (8 feet) long and weigh about 180 kg (400 lbs). Young males are not distinguishable from young females until their dorsal fin begins to grow rapidly or "sprout" after puberty (around 12 years of age).