Spermaceti in the enormous head helps diving, and squid beaks cause ambergris production.
Whaling
Sperm Whales were hunted intensively for their blubber, ambergris, meat and the oil in their head (spermaceti in the spermaceti organ), with over a million thought to have been killed. Although the world population now stands at around 360,000 they are considered ‘vulnerable’ since they have a very low reproductive rate – they only breed every five or so years, gestate for at least a year, wean for a further two or three years, and then take over ten years to become sexually active.
Spermaceti
Spermaceti is found in all whale blubber, but great concentrations of it are found in the spermaceti organ of the Sperm Whale. In the past the practice was to tie the dead whale against the ship, cut a hole in its head, then send in a man with a bucket (not the best of jobs!). 3 tonnes of spermaceti oil could be obtained from a single whale, and it was of great value as a lubricant for precision instruments and in the manufacture of cosmetics.
Diving
One theory about the spermaceti organ in the head of a Sperm Whale likens it to a buoyancy tank. At the surface the oil cools and becomes dense, making the whole whale heavier than water. While actively hunting at depth the oil is warmed up so the whole whale becomes lighter than water. The tail flukes are massive and very heavy, and they are lifted well out of the water at the start of the dive. Put these two things together and you have a heavy object propelled initially by the weight of its tail plummeting down under its own weight. Surfacing is not much more than simply floating up again. However they do it Sperm Whales are phenomenal divers, getting down to 2km or more and able to hold their breath for up to 2hrs. They have anatomical adaptations to help cope with compression due to the enormous pressures of the deep (such as flexible ribs and very wrinkled skin), but there is some evidence (pitting of bones) to suggest that older males, who dive the deepest, might suffer from decompression sickness.
Hunting
The main prey is squid, most famously Giant Squid. Sperm whales do not seem to use their teeth as much as their voice to subdue these giant molluscs. Sperm Whales can make the loudest noise in the animal kingdom (230dB), and it is thought that another function of the spermaceti organ and weird-shaped head might be to focus all this sound energy on the squid. This would certainly surprise the squid, and might shake him up enough to allow capture.
Ambergris
Indigestible squid beaks are often found in Sperm Whale stomachs and since they are often surrounded by ambergris (a substance secreted by the whale’s intestines) it looks as if the ambergris is designed to protect the gut. Ambergris can be collected either from the stomach of a freshly killed whale or found washed up on the beach, and (although foul-smelling initially) was, and still is, of great value in the perfume industry.
Main reference: Collins Wild Guide – ‘Whales and Dolphins’ by Mark Carwardine, 2006.
Other articles by John Blatchford
