Whales

Dwarf Sperm Whale - Kogia sima

The Dwarf Sperm Whale is one of the three species of the sperm whale family. They are rarely sighted at sea so most of our understanding comes from the remains of the dead animal that has been washed up to shore. They make slow, deliberate movements with little splash or blow and usually lie motionless when at the surface of the sea, so they are only observed in very calm seas.

The Dwarf Sperm Whale is the smallest of all whales. It is smaller than the bigger dolphin, being 2.7 meters in length and 250 kg in weight. They are very similar physical and behavioural characteristics as the pygmy sperm whale, however, the Dwarf is slightly smaller and has a larger dorsal fin. Its body is mostly a bluish grey, with a lighter underside. Their flippers are very short and broad. The lower jaw is overhung by their top snout, and contains long, curved, sharp teeth, six of which are in the upper jaw with 14 to 26 in the lower. They feed mostly on squid and crab.

Dwarf Sperm Whales are usually solitary creatures, but are occasionally seen in small groups. The lack of sightings at sea may be more due to its behaviour than true abundance. The species accounted only for 1% of the animals recorded to be seen and occurred in 12% of the herds observed during an aerial survey. Its behaviour is similar to most other small whales, in that they rise to the waters surface slowly and deliberately, then they simply drop out of sight. The Dwarf Sperm whale has an organ in its forehead that enables it to expel a dark reddish substance when it is frightened or attacked, possibly to put off any enemies or predators. One of the few reported behavioural observations was of a mother and calf, together with a mixed school of spotted dolphins who had accidentally encircled them. The female was said to release into the water a cloud of reddish material, presumably faeces, 6-8 times during the course of the set. The mother released the faeces whenever a dolphin approached the calf; she then appeared to hide herself and the calf in the middle of the opaque cloud. The reproductive habits of the Dwarf Sperm Whales are almost completely unknown. At birth, calves are born approximately about 1 m in length and weight about 45 kg. The young reach maturity when they are about 2 m in length.

They prefer deep waters, being more coastal than the pygmy sperm. Its favourite habitat seems to be just off the continental shelf. Strandings have been found in the Atlantic, near the United States in the west, Spain in the east, even as far south as Brazil and the tip of Africa. In the Indian Ocean, specimens have been found on the south coast of Australia, from South Africa right across to Indonesia. They seem to be especially common off the southern tip of Africa and in the Gulf of California