The Sperm Whale (Physeter macrocephalus) is the largest of all toothed whales and is the largest toothed animal alive, measuring up to 18 metres (60 feet) long. Sperm Whales can regularly be seen in the Galapagos waters. The Sperm whale was named after the milky-white waxy substance called ‘spermaceti’ which is found in its head. The Sperm Whale has an enormous head and distinctive shape.
The Sperm Whale is exceptional for its very large head, particularly in males, which is typically one-third of the animals length. The Sperm Whales name ‘macrocephalus’ is derived from the Greek for ‘big 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 they may appear brown in sunlight. White albino whales have also been reported. The brain of the Sperm Whale is the largest and heaviest known of any modern or extinct animal (weighing on average 7 kilograms (15 pounds) 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 whales left. This gives rise to a distinctive bushy blow angled forward. The Sperm Whale has no true dorsal fin, instead a series of ridges are present on the caudal third of the back. The largest was called the ‘hump’ by whalers and is commonly mistaken for a dorsal fin because of its shape. The flukes of a Sperm Whale are 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 measuring 25 centimetres or 10 inches long. Each tooth can weigh as much as one kilogram. The current scientific consensus is that the teeth may be used for aggression between males of the same species as they are not really needed to aid their diet of squid. Bull sperm whales often show scars which seem to be caused by the teeth of other bulls.
Sperm Whales are amongst the most sexually dimorphic (that is, males and females differ greatly) of all cetaceans. Males are typically 30% to 50% longer (16 – 18 metres, 52 – 59 feet) than females (12 – 14 metres, 39 – 46 feet) and are twice as massive (50 000 kilograms for males and 25 000 kilograms for females). At birth both males and females measure about 4 metres (13 feet) in length and weigh around 1,000 kilograms (1 tonne).
Female Sperm Whales give birth once every four to six years and the gestation period is at least 12 months and possibly as long as 18 months. Nursing takes place for two to three years. In males, puberty lasts for about ten years between the ages of about 10 and 20. Males continue to grow into their 30’s and 40’s and only reach their full size when about 50 years old. Sperm Whales live for up to 80 years.
The Sperm Whale holds some natural world records:
Largest known toothed mammal ever.
Sperm Whales have the biggest head for their size of any animal (up to one third of their body length).
Largest brain of any living creature on Earth. The brain of a mature sperm whale weighs 7 kg (15 pounds), though there have been specimens with 9 kg (20 pound) brains.
Largest living carnivore on Earth.
Deepest diving mammal (found at depths of 2,200 metres (7,200 feet) and can hold its breath for up to 2 hours.
Sperm Whales are almost certainly the largest toothed predator that has ever lived, and they have the biggest teeth (25cm or 10 inches long).
Loudest animal in the world. Sperm whale clicks have a source level exceeding 230 dB re 1 micropascal referenced to a distance of 1 metre.
In 1820, a sperm whale estimated to be about 25.9 metres (85 feet) long attacked a Nantucket whaling ship Essex. Only 8 out of the 20 sailors managed to survive and be rescued by other ships.
It is thought that sperm whales have the lowest reproductive rate of any animal – not necessarily a good trait.
The sperm whale has two nostrils – one external nostril, forming the blow hole, and one internal nostril pressing against the bag-like spermaceti container.
One function of the spermaceti organs is a buoyancy or diving organ. Before diving, cold water is brought through the organ and the wax is solidified. The increase in specific density generates a down force (approx 40 kg equiv) and allows the whale effortless sinking. During the chase in deep levels (max 3,000m) the stored oxygen is consumed and excess heat melts the spermaceti. Now only hydrodynamic forces (by swimming) keep the whale down before effortlessly surfacing.
Spermaceti was much sought after by 18th, 19th and 20th century whalers. The substance found a variety of commercial applications, such as watch oil, automatic transmission fluid, lubricant for photographic lenses and delicate high-altitude instruments, cosmetics, additives in motor oils, glycerine, rust-proofing compounds, detergent, chemical fibres, vitamins and 70 or more pharmaceutical compounds.
More About The Sperm Whale
Sperm Whales breathe air at the surface of the water through a single, s-shaped blowhole. The blowhole is located on the left side of the front of the head. They spout (breathe) 3–5 times per minute at rest, but the rate increases to 6–7 times per minute after a dive. The blow is a noisy, single stream that rises up to 15 metres (50 feet) above the surface of the water and points forward and to the left of the whale at a 45 degree angle.
Whales, along with bottlenose whales and elephant seals, are the deepest diving mammals in the world.
They are believed to be able to dive up to 3km (1.9 miles) in depth and 90 minutes in duration to the ocean floor. More typical dives are around 400 metres in depth and 30–45 minutes duration and generally move in a northerly direction. They can dive two miles deep with one gulp of air for two hours. They carry three tonnes of blood which holds enough oxygen to help them achieve their diving depths.
Between dives, the Sperm Whale will come up to the surface for breath and remain more or less still for eight to ten minutes before diving again.
Sperm Whales feed on several species, in particular giant squid, octopuses and diverse fish like demersal rays, but the main part of their diet consists of medium sized squid. Almost all that is known about deep sea squid has been learned from specimens found in the stomachs of captured Sperm Whales.
Sperm Whales are enormous feeders and eat around 3% of their body weight per day. The total annual consumption of prey by Sperm Whales worldwide is estimated to be about 100 million tons – a figure greater than the total consumption of marine animals by humans each year.
The only predator that attacks Sperm Whales, besides human beings, is the Orca. Large, roving pods of Orcas frequently target groups of females with young, usually trying to separate the Sperm Whale calf and kill it. Often, the female Sperm Whales can repel these attacks by forming a circle with their calves in the centre and then violently thrashing their tail flukes, so that no Orca can intervene in the circle. If the Orca pod is extremely large, they may sometimes also kill adult females. Large bull Sperm Whales have no predators, as even Orcas could be killed by these aggressive, powerful creatures.
The physiology of the Sperm Whale has several adaptations to cope with drastic changes in pressure when diving. The ribcage is flexible to allow lung collapse and the heart rate can decrease to preserve oxygen supplies. Myoglobin stores oxygen in muscle tissue. Blood can be directed towards the brain and other essential organs only, when oxygen levels deplete. The spermaceti organ may also play a role.
Female Sperm Whales are extremely social animals. Females stay in groups of about a dozen individuals with their young. Males leave these ‘nursery schools’ at somewhere between 4 and 21 years of age and join a ‘bachelor school’ with other males of a similar age and size. As males grow older, they tend to disperse into smaller groups and the oldest males typically live solitary lives. Yet mature males have been stranded on beaches together, suggesting a degree of co-operation not yet fully understood.
The Sperm Whale is among the most cosmopolitan species in the world and is found in all the oceans and the Mediterranean Sea. The species is relatively abundant from Arctic waters to the equator. Populations are more dense close to continental shelves and canyons, probably because of easier feeding. Sperm Whales are usually found in deep off-shore waters, but may be seen closer to shore in areas where the continental shelf is small.
Sperm Whales are believed to have diverged from other toothed whales early in the evolution of the suborder – around twenty million years ago.
The number of Sperm Whales throughout the world is unknown. Crude estimates, obtained by surveying small areas and extrapolating the result to all the world’s oceans, range from 200,000 to 2,000,000 individuals. Although the Sperm Whale was hunted for several centuries for its meat, oil and spermaceti, the conservational outlook for Sperm Whales is brighter than that for many other whales. Although a small-scale coastal fishery still occurs in Indonesia, they are protected practically worldwide. Fishermen do not catch the deep-sea creatures that Sperm Whales eat and the deep sea is likely to be more resistant to pollution than surface layers.
However, the recovery from the whaling years is a slow process, particularly in the South Pacific, where the toll on males of a breeding age was severe.