Kogia breviceps (Blainville, 1838)

Size

Kogia breviceps, commonly known as the pygmy sperm whale, is similar in size to many dolphins. Newborns are around 1.2 m (3 ft 11 in) long, growing to roughly 3.5 m (11 ft) at maturity. Adult individuals weigh about 400 kg (880 lb).

Coloration

Their underside is creamy, occasionally pinkish, while their back and sides are bluish grey, with considerable intermixing of these two colors. Their shark-like head is large relative to their body size, giving an almost swollen appearance when viewed from the side. Behind each eye, there is a whitish marking often called a "false gill".

Head Features

The lower jaw is very small and positioned low on the head. When viewed from above facing forward, the blowhole is slightly displaced to the left. The dorsal fin is very small and hooked; it is considerably smaller than the dorsal fin of the dwarf sperm whale, and this difference can be used for diagnostic identification.

Distribution and Habitat

Pygmy sperm whales live across the tropical and temperate waters of the Atlantic, Pacific, and Indian Oceans, and are occasionally spotted in colder waters such as those off the coast of Russia. They are rarely sighted at sea, so most available data comes from stranded animals, which makes creating a precise range and migration map difficult. They are thought to prefer offshore waters, and are most often found in depths between 400 and 1,000 m (1,300 to 3,300 ft), especially in areas where upwelling creates local concentrations of zooplankton and prey.

Rarity and Fossils

They are generally described as rare, but occasional clusters of higher-density strandings indicate they may be more common than previously estimated. The total global population of this species remains unknown. Fossils identified as belonging to K. breviceps have been recovered from Miocene deposits in Italy, Japan, and southern Africa.

Reproduction

Detailed information on pygmy sperm whale reproduction is limited. It is believed that mating occurs from April to September in the Southern Hemisphere, and from March to August in the Northern Hemisphere. Individuals reach sexual maturity between 4 and 5 years of age.

Gestation and Birth

Like almost all mammals, pygmy sperm whales are iteroparous, meaning they reproduce multiple times over the course of their lives. After impregnation, the average gestation period is 9 to 11 months. Unusually for cetaceans, females give birth to a single calf head-first.

Calves and Lifespan

Newborn calves measure around 1.2 metres (3 ft 11 in) in length, weigh 50 kg, and are weaned at approximately one year of age. Pygmy sperm whales are thought to live up to 23 years of age.