They are the largest porpoise species, growing up to 7.5 ft (2.3 m) in length and weighing between 370 and 490 lbs (130 and 220 kg). Sexual dimorphism is apparent in body size and shape, with mature males being larger, developing a deeper caudal peduncle, and having a dorsal fin that’s significantly angled forward in comparison to a female’s. Dall’s porpoise calves have a greyish coloration with no frosting on flippers and flukes. Calves measure about 100 cm at birth. Growth rates are similar at first, but at about 2 years old males begin to grow faster than females. Externally, maturity is measured by length which is usually attained at 3 – 5 years old. Sizes vary between populations, but on average females reach a maximum size of 210 cm and males grow to about 220 cm, except in the southern Okhotsk Sea where males can grow as long as 239 cm.