The Hector’s dolphin is the smallest of the world’s dolphin species. Fully mature, adults range in length from 1.2–1.6 m and in weight from 40–60 kg. At birth, Hector’s dolphin calves have a total length of 60–80 cm and weigh 8–10 kg.
The species is sexually dimorphic (females are bigger than males). Their body shape is stocky, with no discernible beak. The most distinctive feature is the rounded dorsal fin, with a convex trailing edge and undercut rear margin.
Hector’s overall appearance is pale grey, but closer inspection reveals a complex and elegant combination of colours. The back and sides are predominantly light grey, while the dorsal fin, flippers, and flukes are black. The eyes are surrounded by a black mask, which extends forward to the tip of the rostrum and back to the base of the flipper. A subtly shaded, crescent-shaped black band crosses the head just behind the blowhole. The throat and belly are creamy white, separated by dark-grey bands meeting between the flippers. A white stripe extends from the belly onto each flank below the dorsal fin.
Males attain sexual maturity between five and nine years of age, and females have their first calf between seven and nine years old. The calving interval is two to four years. This stats mean that Hector’s dolphins, have a low potential for population growth. Maximum population growth rate has been estimated to be 1.8-4.9% per year.