Owen, 1866 - Dwarf sperm whale
The dwarf sperm whale is similar in appearance to the pygmy sperm whale, but has a larger dorsal fin (> 5% of the body length), generally set nearer the middle of the back. Like its congener, the dwarf sperm whale has a shark-like profile (but with a more pointed snout than the pygmy sperm whale).
Dwarf sperm whales have grey (dorsal) to white (ventral) coloration, and a pigment marking shaped like a shark's gill slit on the side of its head. Generally, a pair of short grooves, similar to those in beaked whales, is present on the throat.
There are 8 to 11 (rarely up to 13) pairs of teeth in the lower jaw; sometimes teeth are present in the upper jaw as well.
Can be confused with
Dwarf sperm whales are most likely to be confused with pygmy sperm whales, which are very similar in appearance. Besides reaching smaller maximum lengths, dwarf sperm whales have taller, more dolphin-like dorsal fins, set more toward the middle of the back. However, because sizes overlap and dorsal fins are variable in size and position, many sightings at sea of Kogia whales may not be identifiable to species.
Adults of this species are up to 2.7 m long and may weigh up to 210 kg. Length at birth is about 1 m.
The dwarf sperm whale, like the pygmy sperm whale, is known mostly from strandings. It has rarely been positively identified in encounters at sea. It appears to be distributed widely in tropical to warm temperate zones, apparently largely offshore.
Biology and Behaviour
Group sizes tend to be small, most often less than 5 individuals (although groups of up to 10 have been recorded). This species, like the pygmy sperm whale, is also shy and undemonstrative when observed at sea. When startled, dwarf sperm whales, and possibly pygmy sperm whales, may leave a large rust-coloured cloud of fecal material behind as they dive.
In at least one area, there appears to be a calving peak in summer.
Dwarf sperm whales appear to feed primarily on deep-water cephalopods.
Some small scale catches of dwarf sperm whales have occurred in Japan and in St. Vincent in the Lesser Antilles. Also, substantial numbers appear to be taken each year in gillnets in the Indian Ocean, and possibly elsewhere.