Narwhal — The Narwhal (Monodon monoceros) is an Arctic species of cetacean. It is a creature rarely found south of latitude 70°N. It is one of two species of white whale in the Monodontidae family (the other is the Beluga whale). It is possibly also related to the Irrawaddy dolphin.
The most conspicuous characteristic of male narwhal is their single extraordinarily long tusk, an incisor that projects from the left side of the upper jaw and forms a left-handed helix. The tusk can be up to three metres (nearly 10 ft) long (compared with a body length of 7–8 m [23-26 ft]) and weigh up to 10 kilograms (22 lbs). About one in 500 males has two tusks, which occurs when the right tooth, normally small, also grows out. Although rare, a female narwhal may also produce a tusk. There is a single recorded case of a female with two tusks.
The purpose of the tusk has been the subject of much debate. Early scientific theories suggested that the tusk was used to pierce the ice covering the narwhal’s Arctic Sea habitat. Others suggested the tusk was used in echolocation. More recently, scientists believed the tusk is primarily used for showmanship and for dominance: males with larger tusks are more likely to successfully attract a mate. This hypothesis was suggested by the activity of “tusking”, in which two males rub their tusks together.
However, recent work by a research team led by Martin Nweeia suggests that the tusk may in fact be a sensory organ. Electron micrographs of tusks revealed millions of tiny, deep tubules extending from the tusk’s surface, apparently connecting to the narwhal’s nervous system. While such tubules are present in the teeth of many species, they do not typically extend to the surface of healthy teeth. The exact sensory purpose of the tusk remains unknown, but scientists now hypothesize that it may detect temperature, salinity, pressure, and/or particulate makeup of the water in which the narwhal swims. Unlike the tusks of elephants, narwhal tusks do not regrow if they break off. If damaged, however, the tusks can repair themselves to a certain extent.
Male narwhals weigh up to 1,600 kg (3,500 lb), the female around 1,000 kg (2,200 lb). Most of the body is pale with brown speckles in colour, though the neck, head and edges of the flippers and fluke are nearly black. Older animals are usually more brightly coloured than younger animals.