The best sperm whale

The best largest of the toothed whales and the largest predatory animal on earth, sperm whales tackle prey up to 10m/33ft long. They are also the deepest-diving mammals, able to descend an estimated 3,000m/10,000ft. Sperm whales mature slowly- calves begin taking solid food at 2 years, but may continue to supplement this milk for 10 years or so. This slow reproductive rate makes them vulnerable to over-exploitation, and they suffered heavy losses before hunting was banned in the 1980s. The oil inside the head, known as spermaceti, was used as a high-quality lubricant. In life, the spermaceti is thought to control buoyancy and focus sound. Also of value are the teeth, used in scrimshaw, and ambergris- a grey substance voided from the gut and used in perfume making.