Sperm Whale, the Blue Planet’s greatest free diver

Cases of death of marine species due to marine debris have been increasing in recent years. One of many is the discovery of a sperm whale carcass on the coast of North Kapota Village, Wakatobi National Park, Southeast Sulawesi in 2018. The whale measuring 5.5 meters long and 437 cm wide was found dead and already starting to rot. Although the cause of death is not known, garbage with a weight of 5.9 kg is suspected to be the main cause of death for this protected mammal.

Sperm whales (Physeter macrocephalus) is not only famous for its ambergris, but they are also the largest animal in the toothed whale group as well as the largest toothed animal in the world. This giant marine mammal can grow to a length of 20 meters. They also have the largest brains of all known animals. Sperm whales are so named because of the milky white material found on the head of the spermaceti. The large head of the sperm whale is the hallmark of this species, especially in males, the head can reach a third of the body length. The dorsal skin of the sperm whale is wrinkled and distinct from the smooth skin of most other large whales. Sperm whales are the same size between males and females at birth, but reaching adult, the males measuring up to 20 meters and weighing up to 57,000 kilograms or 30% to 50% longer and three times larger than females. Sperm whales have 20-26 pairs of conical teeth on their lower jaws. Each tooth can weigh up to one kilogram. However, it turns out that they do not use these teeth for hunting. They actually prefer to swallow their prey directly without tearing it first.

Ever imagined about the animal with the loudest sound in the world? Who would have thought, the title was actually owned by this marine mammal. They can create a magnitude of 230 decibels for one click they sound. That means, the sound of a sperm whale exceeds the noise of a jet engine.

Sperm whales can live up to 70 years or more. They are among the most cosmopolitan species in the open ocean. They can be found in almost all ocean that are not covered with ice more than 1,000 meters deep, except in the Black Sea and possibly the Red Sea. Shallow inlets to the Black and Red Seas may explain the absence of this species. The bottom layer of the Black Sea is also anoxic and contains high concentrations of sulphur compounds such as hydrogen sulphide. In some areas, particularly in the western part of the North Atlantic, sperm whales, especially males, can be found in shallow water. Their distribution depends on food sources and conditions suitable for breeding. Sperm whale migration is not as well predicted or understood as baleen whale migration. Several populations appear to have different migration patterns based on life history status, with adult males making long oceanographic migrations to temperate waters while females and juveniles settle in tropical waters year-round.

Sperm whales form highly stable social groups based around related females and their offspring. These groups tend to live in open ocean areas and are occasionally visited by males who range widely across the oceans. Calves are born after a 14–16-month gestation period and stay with their mothers for many years. A calf will start to eat solid foods by the age of 1 year but may continue suckling for several more years until the next calf is born. Young males will leave their female family unit when 4-21 years old and will often join a ‘bachelor herd’ with other males of approximately the same age and size. These bachelor herds are observed in colder waters toward the poles. Females, however, stay with their family unit of 4-21 individuals and help to care for young in the group until they are mature enough to have their own calves. Like killer whales, they are one of the only mammal species other than humans, in which females continue to live and play a role in family/social groups after they have stopped producing calves. Fully mature males return to the warmer waters where the females are found in order to mate, sometimes spending only a few minutes or hours with a group before moving on again           

Since they are marine mammals, sperm whales need oxygen to breathe. These marine mammals inhale/exhale an average of 3-7 times per minute depending on how active they are. Their ability to dive to depths of more than 2.9 km making them one of the deepest diving marine mammals in the world. During the hunt for food, they are able to hold their breath for more than 60 minutes. After a long, deep dive, the sperm whale comes to the surface to breathe and recuperate for a few minutes before starting the next dive. Because they spend most of their time in deep, dark water, echolocation allows them to maintain a thorough awareness of their surroundings. Sperm whale is a type of carnivorous whale. In one day at least they can eat up to 1 ton of giant squid and fish in deep waters. Sperm whales can eat as much as 3 to 3.5 percent of their body weight per day.

Killer whales have been observed attacking sperm whale pods, and large sharks are also thought to be potential predators of calves. Sperm whales in some parts of the world have a unique response to attacks, gathering into a ‘marguerite’ or wagon wheel formation – in which all members of the group position themselves with their heads in the center and their tails facing outward like the spokes of a wheel. They then fend off attack by slashing their tails back and forth. Sometimes a vulnerable calf or injured whale is positioned at the center of the formation.

Sperm whales face a number of threats today, including entanglement in fishing gear, ingestion of fishing gear and marine debris, and ship strikes. The latter is thought to be one of the main drivers of sperm whale population decline in the Mediterranean and a major threat to survival of sperm whales in the Canary islands. They were historically heavily hunted. Commercial whaling from 1800 to the 1980s greatly decreased sperm whale populations worldwide. The International Whaling Commission placed a moratorium on commercial whaling in 1986. This species is still recovering, and its numbers are likely increasing. Today, sperm whales are globally designated as Vulnerable on the IUCN Red List of Threatened Species. The genetically distinct Mediterranean subpopulation, however, is considered endangered, due to the fact that there are estimated to be fewer than 2,500 individuals and the persistent threat of ship strikes and entanglements throughout the area. Sperm whales are listed on Appendix 1 of the Convention on Migratory Species (CMS).