Sperm Whale

physeter macrocephalus

Largest of all toothed whales (odontocetes), the sperm whale gets its name from its spermaceti organ, a very large, oil-filled chamber that occupies most of the animal’s enormous head.

Appearance: The sperm whale body is relatively short and robust, with a wrinkled surface appearance aft of the head. The head itself is very large, squared-off and blunt; in males, it accounts for about a third of the animal’s total length and mass and contains the spermaceti organ, a specialized and hypertrophied melon housing a large reservoir of the oily liquid from which it takes its name. The jaw is small, underslung and inconspicuous. A few ventral throat pleats can be seen just after of it.

After of the relatively small and rounded dorsal fin, a series of bumps or ‘knuckles’ may form a dorsal ridge along the tailstock. The single blowhole is located forward on the left side of the head. The comparatively small eyes are found just above and behind the angle of the jaw; this awkward location restricts upward vision, so that the animal must turn longitudinally to look at the objects above it.

Key CharacteristicsSperm Whale

  • Huge, squared-off head
  • Low hump-like dorsal fin
  • “Knuckles” from hump to flukes
  • Single, slit-like blowhole
  • Dark body with wrinkled skin
  • Broad flukes raised on diving
  • Sideways, forward-angled blow
  • Often motionless at surface
  • Dives for long periods

Dorsal Fin: squat and hump-like. Females may display whitish callosities at the tip.

Flippers: short and wide, with broad but rounded tips.

Flukes: broad and triangular with a distinct notch in the middle, measuring as much as 5m from tip to tip. The trailing edges of the flukes often bear a distinct pattern of scars and other marks.

Jaw & Teeth:  here is usually no dentition in the upper jaw (though tiny, non-erupting teeth have sometimes been found) the lower jaw is long and narrow, and holds between 36 and fifty teeth. These are large and peg-like and up to 25cm long, fitting into sockets in the upper jaw.

Colouration: the body is a fairly uniform dark grey or dark brown, though lighter streaks and spots may appear It is sometimes scarred, especially on the head and particularly in males, who use their teeth on one another in mating battles. The lips are light-coloured, often white, usually mottled with dark and light patches. The underside of the body is a lighter grey, often showing patches of white pigmentation.

Group Size: highly variable. Normally found as solitaries, pairs or in small pods of up to 24, while groups of 100—250 individuals have been observed on the move. Maternal pods comprising females and young seem to live in stable long-term groups, but may disperse into clusters when feeding.

Behavior: On the move, sperm whales swim side by side or, occasionally, in single file. Partial breaching is sometimes observed. Other characteristics behavior traits are lobtailing, ‘headout’ (at about 300), and rolls in which the flippers and belly become visible.

‘Flukes up’ signals a steep dive of longer duration. Atypical dive sequence commences with a forward rocking motion in which the upper part of the head breaks the surface. Only two-thirds of the body can be seen during the blow. Next, the body straightens out, then the back arches gently. At this point the whale may disappear, dipping just below the surface. After accelerating forward, it reappears, showing part of its head, back and hump, and begins to arch its back till it is high out of the water. The flukes and rear third of the body are then raised high into the air before the animal submerges vertically, creating very little disturbances in the water.

On a shallow dive, air is often expelled while submerging. Sperm whales are timid and should be approached cautiously. When threatened, these animals may release a cloud of reddish-brown intestinal fluid.

Diet: primarily epipelagic and mesopelagic cephalopods, including giant squid. Sperm whales also eat fish and occasionally crustaceans.

Dive Depth: The sperm whale is the champion diver among cetaceans and quite possibly the deepest-diving of all air-breathing animals. It can reach depths of over 2km and stay submerged for well over an hour. Average foraging dives are 20-5-min, reaching depths of 300-600m. Dives in continental-shelf waters are of briefer duration, around 10-20min.

Distribution: nomadic, typically within a 1,500 km (800mm) ‘home range’. May occur inshore when relocating but otherwise pelagic. Sperm whales prefer continental slopes and ridges characterized by high secondary production.

Sightings: Sri Lanka – common all year round ; abundant March- April, less frequent in June-July. Maldives – regular. India –  uncommon.

Blow: the sperm whale’s unique, angled blow, low (<2-4m) and bushy, is a reliable identifier of the species.