There are three living species of sperm whales which belong to the superfamily Physeteroidea. These whales belong to the Phylum Chordata, Class Mammalia, Order Artiodactyla, and Infraorder Cetacea. Fossil evidence suggests that sperm whales have been in existence for over 25 million years. The evidence also shows close relationships with the Ziphiidae, Mysticeti, and Platanistidae. The three species of sperm whale include the sperm whale, pygmy sperm whale, and dwarf sperm whale. The first belongs to the genus Physeter whereas the last two are of the genus Kogia. These whales inhabit most of the major temperate and tropical ocean waters. They share certain characteristics including the location of the blowhole, simple teeth arrangements, and other general body and behavioral features. They also rely on features like echolocation, have spermaceti, dive to look for food, and eat squid and some fish species. Just like most whales and sea animals, fishing and pollution threaten the existence of these whales. Below are general descriptions and characteristics of the three types of whales.
3. Sperm Whale (Physeter macrocephalus)
The other name of this whale is cachalot and it is the largest of the extant sperm whale species as well as the only surviving member of Physeter genus.
They have big, block-shaped heads that cover between a third to a half of their entire bodies. Being the largest toothed whale, on average, newborns, females, and males measure 13, 36, and 52 feet respectively and weigh 1.1, 15, and 45 short tons respectively. Some adults may grow up to 67 feet. Sperm whales also have the largest brain ever found on any species, extinct or extant. All sperm whales have spermaceti on their heads which generate clicks they use for communication, echolocation, and other sensory functions.
Sperm whales inhabit all the oceans and seas, from the poles to the equator. They prefer waters of up to 3,300 feet or deeper and free of ice. Adults prefer higher latitudes but young ones live in tropical and temperate waters. Sperm whales like areas near continental shelves and canyons. They dive to depths of between 2,620 feet and 6,600 feet to look for food. Under the water, they dive for up to one hour or more.
Sperm whales feed on giant squid, colossal squid, octopuses, and other fish. These whales eat food equivalent to 3% of their body mass daily. Annual estimates indicate that all the global sperm whales eat approximately 100 million short tons of prey, compared to global human consumption of seafood which stands at 127 million short tons.
Non-breeding adults usually live in solitary but females and younger males exist in groups. Occasionally, mature males may form small age-based groups. Groups of females and younger males, normally between six and twenty in number, stick together for years and no individual leaves or joins the group. Members of the group socialize by producing coda type of vocalization and rubbing each other’s bodies. Sperm whales normally do not have bonds with other whale species apart from bottlenose dolphins that occasionally swim alongside sperm whales.
Killer whales are sperm whale’s primary predator; however, pilot whales and false killer whales normally intimidate them. Sperm whales have also adapted to defense mechanism like the 'marguerite formation' where they protect the vulnerable member.
2. Pygmy Sperm Whale (Kogia breviceps)
This whale is slightly bigger than dolphins. They measure around eleven feet at physical maturity and weigh approximately 880 lb. K. breviceps have bluish-gray backs and pinkish underside. Their heads are larger compared to their bodies. Their big heads resemble those of sharks. Other features include a small dorsal fin, left-leaning blowhole, a spermaceti organ, and small lower jaw. Pygmy sperm whales have 20-32 teeth on the lower jaw. For evading predators and confusing preys, they have reddish-brown “ink” fluid that they eject to block the predator’s view. Presence of magnetic crystals in this whale’s brains suggests that they may use magnetoreception for navigation.
Pygmy whales inhabit the tropical and temperate waters of the Atlantic, Indian, and Pacific Oceans with depths between 1,300 and 3,300 feet. Russian fishermen and researchers laid several claims of spotting pygmy whales in the cold waters near the country.They mate from April to September within the southern hemisphere waters. They also have eleven months of gestation periods and newborns measure about three feet and 11 inches. These whales have diverse movements.
The animals can lie motionless on the water surface, do little splashes, dive slowly, and rise to the surface slowly. Pygmy sperm whales live solitarily, in pairs or small group of up to six. They also have the capability of diving for between 11 and 45 minutes and produce click sounds. They prey on glass squid, lycoteuthid squid, ommastrephid squids, and octopuses.
1. Dwarf Sperm Whale (Kogia sima)
This whale is the smallest of any whale species, grows up to 8.9 feet long and weighs up to 550 lb. They have slow but calculated movements, and like the pygmy sperm whale, they can lie motionless on calm water surfaces. Although resembling the pygmy sperm whale, they are smaller and have bigger dorsal fins. They are bluish-gray in color and have almost white undersides. The dwarf sperm whale also has small lower jaws.
They live in solitary but may also exist in small pods. The pregnancy time for females lasts nine to eleven months, after which calving lasts for four to five months. They generally feed on squids and crabs. These whales, just like their counterparts the pygmy sperm whales, have a reddish-brown “ink” fluid which they eject to deter predators.
Dwarf sperm whales prefer deep waters near the coasts, just off the continental shelf. Within the Atlantic Ocean, they are common off the coasts of Virginia, Spain, Brazil, parts of Africa, and the UK. In the Indian Ocean, they inhabit areas near Australia, Indonesia, and parts of Africa. Habitats in the Pacific include off the coasts of Japan, Russia, and British Columbia. Since dwarf sperm whales inhabit waters close to the shores, they face threats brought about by human activities like illegal fishing and pollution. This situation leads to heightened conservation measures by different international bodies.