Pygmy sperm whale
Pygmy sperm whales resemble dwarf sperm whales and were not recognised as a separate species until 1966. As with the dwarf sperm whale, the pygmy sperm whale appears to have an unusual defence mechanism. When startled, it releases a cloud of reddish-brown intestinal fluid and then dives. This may act as a decoy very similar to that of squid ink.
The pygmy sperm whale has a small robust body and a squarish head with a single blowhole set slightly left of centre. It has a small underslung jaw, with 9-16 pairs of teeth in the lower jaw, and occasionally 3 pairs of teeth in the upper jaw. Just behind the eye is a false gill, and this feature (which may be an adaptation to help them 'mimic' their main predators, sharks), along with the underslung jaw often causes the pygmy sperm whale to be initially confused for a shark when sighted or stranded. Its dorsal side is grey to blue-grey, which fades to whitish or sometimes pale blue or pinkish on the belly. It has a small circular white patch in front of the eye, whilst the eye itself is circled in black. In the wild it may be confused with the very similar looking dwarf sperm whale and even with stranded individuals, genetic confirmation of the species is sometimes required.
Pygmy sperm whales are rarely seen at sea and most of what is known about them is derived from stranded individuals. When they are spotted at sea, they are usually resting, floating motionless at the surface with the back and head exposed, and the tail hanging loosely in the water. Pygmy sperm whales are slow, deliberate swimmers and, unusually for their size, drop below the surface like a stone rather than rolling like most other cetaceans. They travel alone or in groups of six or seven animals. They breach occasionally, and are shy around boats, allowing approaches mainly when they are resting. They are not very vocal, but probably use echolocation clicks to locate their prey.
While not hunted commercially, small numbers of pygmy sperm whales have been taken in some coastal areas. They tend to prefer warmer, deeper waters in the tropical to temperate zones of all the world's oceans. There have been sightings of pygmy sperm whales in all temperate subtropical and tropical seas, but most information about their distribution comes from strandings. The worldwide population is unknown, and the IUCN lists the whale as Data Deficient. The species is thought to be particularly affected by environmental change, marine debris, and anthropogenic noise.