(de Blainville, 1838) - Pygmy sperm whale
Distinctive Characteristics
Pygmy and dwarf sperm whales are very difficult to detect, except in extremely calm seas. Pygmy sperm whales have a shark-like head with a narrow underslung lower jaw. The flippers are set high on the sides near the head. The small falcate dorsal fin (< 5% of the body length) is usually set well behind the midpoint of the back.
Pygmy sperm whales are countershaded, ranging from dark grey on the back to white below. Often the belly has a pinkish tone. There is a light coloured bracket mark, dubbed the “false gill,” along the side between the eye and the flipper. The lower jaw contains 12 to 16 (sometimes 10 or 11) pairs of long, fang-like teeth that fit into sockets in the upper jaw. There are usually no teeth in the upper jaw.
Can be confused with
Pygmy and dwarf sperm whales are somewhat difficult to distinguish at sea. Pygmy sperm whales grow to somewhat greater total lengths, and have smaller, more rounded dorsal fins, set farther back on the body. There is some degree of overlap in most of characteristics of these 2 species, and identifications must be made cautiously.
Size
Adult pygmy sperm whales are 2.7 to 3.4 m long, and newborns are about 1.2 m. Adults may weigh as much as 400 kg.
Geographical Distribution
Pygmy sperm whales are known from deep waters in tropical to warm temperate zones of all oceans. They appear to be especially common over and near the continental slope.
Biology and Behaviour
Most sightings of pygmy sperm whales are of small groups of less than 5 or 6 individuals. Almost nothing is known of the behaviour and ecology of this species. They are rarely seen alive at sea, but they are among the most frequently stranded small whales in some areas. When seen at sea, they generally appear slow and sluggish, with no visible blow.
Very little is known of the reproductive biology of the pygmy sperm whale.
Studies of feeding habits, based on stomach contents of stranded animals, suggest that this species feeds in deep water on cephalopods and, less often, on deep-sea fishes and shrimps.
Exploitation
Pygmy sperm whales have never been hunted commercially. In recent years, however, a few have been killed in Sri Lanka's gillnet fisheries, and it is likely they are killed in gillnets elsewhere as well. Small numbers have been taken in coastal whaling operations off Japan and Indonesia.
IUCN Status
Insufficiently known.