The Pygmy Sperm Whale is one of three species of toothed whale in the sperm whale family. They are not often sighted at sea, and most of what is known about them comes from the examination of stranded specimens.
Physical Description Edit
The pygmy sperm whale is not much larger than many dolphins. They are about 1.2 meters (3 ft 11 in) at birth, growing to about 3.5 meters (11 ft) at maturity. Adults weigh about 400 kilograms (880 lb). The underside is a creamy, occasionally pinkish, colour and the back and sides are a bluish grey; there is, however, considerable intermixing 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. There is a whitish marking, often described as a "false gill", 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. The pygmy sperm has between 20 and 32 teeth, all of which are set into the lower jaw. Unusually, this species teeth lack enamel due to a mutation in the necessary gene, although enamel is present in very young individuals.
The pygmy sperm whales feed primarily on cephalopods, most commonly including bioluminescent species found in midwater environments. 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.
The whale makes very inconspicuous movements. It rises to the surface slowly, with little splash or blow, and will remain 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 of up to six. Dives have been estimated to last an average of eleven minutes, although longer dives of 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.