The sperm whale family has just three species, all of which occur in Indian waters. The Sperm Whale Physeter macrocephalus, growing to more than 18 m in length, is much larger than the Pygmy and Dwarf Sperm Whales Kogia breviceps and K. simus, which attain lengths of only 3 m or so. The Dwarf Sperm Whale is one of the smallest cetaceans known as a ‘whale’. Features common to the three species include a large melon, which is particularly pronounced in the Sperm Whale, a narrow lower jaw under the head, and a lack of functioning teeth in the upper jaw. Some taxonomists consider that the two smaller species should be placed in the separate family Kogiidae.
Sperm Whales were subjected to intense whaling for valuable substances like spermaceti oil and ambergris during the 19th and 20th centuries. Despite this, they are relatively abundant still. Many of the open boat whalers lost their lives hunting Sperm Whales.
The Pygmy and Dwarf Spem Whales differ from the Sperm Whale in having dorsal fins. Little is known about them. They are small and unobtrusive, and most of what is known comes from strandings. Both species feed on squid, cuttlefish and fish, obtaining these from the slopes of continental shelves. They dive down to about 300 m in search of food.