Sperm Whale

The Sperm Whale (Physeter macrocephalus) is the largest of the toothed whales and is believed to be the largest toothed animal to ever inhabit the planet. more...

(The baleen blue whale is larger, and invertebrates such as the lion's mane jelly fish or the Portuguese man of war may be longer.) The whale was named after the milky-white substance spermaceti found in its head and originally mistaken for sperm. The Sperm Whale's enormous head and distinctive shape, as well as its central role in Herman Melville's Moby-Dick, have led many to describe it as the archetypal whale. Partly due to Melville, the Sperm Whale is commonly associated with the mythological Leviathan of Biblical lore.

Historically the Sperm Whale has also been known as the Common Cachalot. The word cachalot is originally Portuguese (cachalote), probably coming from cachola, a colloquial term for head. Sperm Whales were hunted until recently in Portuguese atlantic archipelago of Azores.

Physical description

The Sperm Whale is exceptional for its very large head, particularly in males, which is typically one-third of the animals' length. Indeed, the species name macrocephalus is derived from the Greek for "big head" (strictly: long head). In contrast to the smooth skin of most other large whales, the skin on the back of the Sperm Whale is usually knobbly and has been likened to a prune by whale-watching enthusiasts . They are uniformly grey in colour though may appear brown in sunlight (the "Great White Whale" of Melville's novel, if such an animal existed, was an albino, and white sperm whales have been reported in reality as well). Perhaps unsurprisingly, the brain of the Sperm Whale is the largest and heaviest of all animals ever (weighing on average 7 kg in a grown male). However, the brain is not large relative to body size.

The blowhole is situated very close to the front of the head and shifted to the whale's left. This gives rise to a distinctive bushy blow angled forward. The dorsal fin is set about two-thirds of the way down the spine and is typically short and shaped like an equilateral triangle. The fluke is also triangular and very thick. Flukes are lifted very high out of the water before a whale begins a deep dive.

Sperm Whales have 20–26 pairs of cone-shaped teeth in their lower jaw. Each tooth can weigh as much as one kilogram. The reason for the existence of the teeth is not known with certainty. It is believed that they are not necessary for feeding on squid (see Feeding below) and indeed healthy well-fed Sperm Whales have been found in the wild without teeth. The current scientific consensus is that the teeth may be used for aggression between males of the same species. This hypothesis is consistent with the conic shape and wide spacing of the teeth. Rudimentary teeth are also present in the upper jaw, but these rarely open into the mouth.

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