The pygmy sperm whale (Kogia breviceps ) is one of two extant species in the family Kogiidae in the sperm whale superfamily. They are not often sighted at sea, and most of what is known about them comes from the examination of stranded specimens.
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 m (11 ft) at maturity. Adults weigh about 400 kg (880 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. 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.
Fossils identified as belonging to K. breviceps have been recovered from Miocene deposits in Italy, Japan, and southern Africa.
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.
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 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.
Pygmy sperm whales and dwarf sperm whales are unique among cetaceans in using a form of "ink" to evade predation in a manner similar to squid. Both species have a sac in the lower portion of their intestinal tracts that contains up to 12 liters of dark reddish-brown fluid, which can be ejected to confuse or discourage potential predators.
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, and are weaned around one year of age. They are believed to live up to age 23.
In 1985, the International Whaling Commission ended sperm whaling.
The pygmy sperm whale is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS) and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS). The species is further included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU) and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU).
As not much is known about this species, as well as due to the whaling and conservation laws in place for marine mammals, it is listed as “lower risk least concern” in the IUCN Red list. However, it faces some modern day issues; it is one of the most common stranded species in Florida sound. Due to its slow-moving and quiet nature, the species is at a higher risk of boat strikes. Its small size also allows for it to become a byproduct of commercial fishing, caught in seine nets. Anthropogenic noise caused by military activity and shipping is another issue affecting this species, as it echolocates. Pygmy sperm whales have also repeatedly been found stranded with plastic in their stomachs.
