Pygmy Sperm Whale

The pygmy sperm whale is not much larger than many dolphins. They are about 1.2 m (3 ft 11 in) at birth, growing to about 3.5–3.8 m (11–12 ft) at maturity. Adults weigh about 400–450 kg (880–990 lb). The underside is a creamy, occasionally pinkish colour and the back and sides are a bluish grey; however, considerable intermixing occurs between the two colours. The shark-like head is large in comparison to body size, given an almost swollen appearance when viewed from the side. A whitish marking, often described as a "false gill", is seen behind each eye.

The lower jaw is very small and slung low. The blowhole is displaced slightly to the left when viewed from above facing forward. The dorsal fin is very small and hooked; its size is considerably smaller than that of the dwarf sperm whale and may be used for diagnostic purposes.

Pygmy sperm whales are found throughout the tropical and temperate waters of the Atlantic, Pacific, and Indian Oceans, and occasionally among colder waters such as off Russia; a 2026 eDNA survey also suggests that the species inhabits the Mediterranean Sea. However, they are rarely sighted at sea, so most data come from stranded animals—making a precise range and migration map difficult. They are believed to prefer off-shore waters, and are most frequently sighted in waters ranging from 400 to 1,000 m (1,300 to 3,300 ft) in depth, especially where upwelling water produces local concentrations of zooplankton and animal prey. Their status is usually described as rare, but occasional patches of higher-density strandings suggest they might be more common than previously estimated. The total population is unknown.

Analysis of stomach contents suggests that pygmy sperm whales feed primarily on cephalopods, most commonly including bioluminescent species found in midwater environments. Most of the cephalopod hunting is known to be pelagic, and fairly shallow, within the first 100 m (330 ft) of the surface. The most common prey are reported to include glass squid, and lycoteuthid and ommastrephid squid, although the whales also consume other squid, and octopuses. They have also been reported to eat some deep-sea shrimps, but, compared with dwarf sperm whales, relatively few fish.

Predators may include great white sharks and killer whales.

The whale makes very inconspicuous movements. It rises to the surface slowly, with little splash or blow, and remains there motionless for some time. In Japan, the whale was historically known as the "floating whale" because of this. Its dive is equally lacking in grand flourish—it simply drops out of view. The species has a tendency to back away from rather than approach boats. Breaching has been observed, but is not common.

Pygmy sperm whales are normally either solitary or found in pairs, but have been seen in groups up to six. Dives have been estimated to last an average of 11 minutes, although longer dives up to 45 minutes have been reported. The ultrasonic clicks of pygmy sperm whales range from 60 to 200 kHz, peaking at 125 kHz, and the animals also make much lower-frequency "cries" at 1 to 2 kHz.

Although firm details concerning pygmy sperm whale reproduction are limited, they are believed to mate from April to September in the Southern Hemisphere and March to August in the Northern Hemisphere. These whales become sexually mature at age 4–5, and like virtually all mammals, are iteroparous (reproducing many times during their lives). Once a female whale is impregnated, the average gestation period lasts 9–11 months, and unusually for cetaceans, the female gives birth to a single calf head-first. Newborn calves are about 1.2 metres (3 ft 11 in) in length, weighing 50 kg (110 lb), and are weaned around one year of age. They are believed to live up to age 23.

Pygmy sperm whales have never been hunted on a wide scale. Land-based whalers have hunted them from Indonesia, Japan, and the Lesser Antilles. This species was impacted by whaling in the 18th and 19th centuries, as sperm whales were especially sought after by whalers for their sperm oil, produced by the spermaceti organ. The oil was used to fuel kerosene lamps. Ambergris, a waste product produced by the whales, was also valuable to whalers as it was used by humans in cosmetics and perfume.

They were not as heavily hunted as their larger counterpart Physeter macrocephalus, the sperm whale, which typically weigh 50 tons, thus preferred by whalers. The pygmy sperm whale is also rather inactive and slow rising when coming to the surface and as such do not bring much attention to themselves. However, they were easy targets, as they tended to swim slowly and lie motionless at the surface.