Baleen whale

Baleen whale

Scientific Classification
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Mammalia Order: Cetacea Suborder: Mysticeti
Families
Balaenidae Balaenopteridae Eschrichtiidae Neobalaenidae Janjucetidae
Hervy Bay Whales

Mysticeti is the taxonomic suborder which contains the baleen whales, containing 4 families, 9 genera, and 14 species. The name baleen whale is derived from from the baleen plates in their mouth which collect small particles of food, mainly of krill, plankton and small fish. Baleen whales only have teeth during their embryonic stage.[1] The plates are made of keratin which is a hard and tough protein fiber.

The size of the whales depends on the species. [2] The humpback and the Blue whale are perhaps the best known of the baleen whales with the latter being the largest and loudest whale. Baleen whales are present all over the world's oceans and can be found in both Arctic and tropical waters. However, some species are limited in their range.[3] There are two main differences between Baleen whales and Toothed whales. First, the Baleen whale is a filter feeder, whereas the toothed whales hunt larger forms of prey. Second, Baleen whales are generally larger than toothed whales, with females larger than males.[4]

Anatomy

The Baleen Plate of a Baleen whale

Mysticeti are filter feeders whose characteristics include lack of functional teeth, large body size, and a short neck. Baleen whales do not have teeth because they have baleen plates which filter small particles of food. The Baleen plates are made of keratin which is a protein that forms hard and tough non-mineral structures in many animals.[5] Baleen, which is also known as a whalebone, can be 2 to 12 ft long, depending on the species. Baleen has been used in many ways in human life, such as in buggy whips, parasol ribs and women's clothing (corsets). Today, whalebone (baleen) has generally been replaced by plastic. [6]

Baleen is an inflexible substance that hangs from the upper jaw. The whales scoop up ocean water and then force it out of the sides of their mouths through the baleen. This filters the prey out on the inside of the mouth so it can be swallowed.[7] For example, the Humpback whale, included among the Baleen whales, has vertical grooves that can expand to help collect the food into the mouth.[8] The Humpback whale has 6 important external feature: blow holes, baleen, flukes, median notch, eye, and pectoral fin. In mysticeti, the Blue whale is the largest and loudest whale, about 93 feet long and weighing 180 tons. They can produce a low frequency moan at a sound level of 188 decibels which can be heard over thousands of miles. A sound of the same intensity would be quieter in air (63 dB quieter according to one reference) [9] and underwater ears function differently than ears built to function in the air. The most musical and the most often heard whale is the Humpback whale, whose songs range in frequency from 20-9,000 Hertz.[10]

Reproduction

The female baleen whales come into a period of sexual receptivity once a year.[11] Among Gray whales, the female chooses one male out of a breeding group, often the male that has the largest body. Partners can change when the males fight each other to get access to a female, because the female mates with the winning male. A female Baleen whale moves to warmer, summer feeding grounds to give birth to her calf in warm waters because it helps the calf survive. Cold water increases heat loss which would be a big problem for a calf, and also, the female saves more energy in the warm water than the cold water.[12] The Humpback whale reaches sexual maturity at 6-10 years, the female Humpback whale bears a calf every 2-3 years, after a gestation period of 12 months. A newborn calf is about 10-15 feet long and weighs 1 ton. The female feeds them with her milk, until after a year she weans her calf to feed on krill, small shrimp and a lot of small fish.[13]

Ecology

Map of distribution of Humpback whales, Finback whales, Right whales

The Baleen whale can be found in all oceans, from the polar to the tropical areas, but differ widely in occurrence. For example, the Southern Right whales, Northern Right whales and Bowhead whales are very difficult to find. Yet, the Fin whales, Minke whales, Sei whales, Blue whales and the Humpback whales are spread all over the world. [14]

The Baleen Whales show seasonal migratory patterns; when summer comes they go to colder areas to feed, and to warmer areas during winter months. However, some of the mysticetes, such as the minke whale, do not travel far. The baleen whale usually travels alone or with some small group. For example, in the winter time the Gray whale travels around the Gulf of California. After they give birth, they move to the Bering Sea, which is the longest migration, about 10,000 km. Also the Humpback, in winter time, travel around Hawaii, while, in spring time, they cross the Pacific ocean to reach the Bering and Chukchi Sea for summer. [15]

Baleen Whale Sounds

Whales sing songs to communicate with other whales. The term song refers to the pattern of sounds made by the species of whale, especially the Humpback whale, which seems similar to human song.[16] Baleen whales generally make sounds that are low in frequency and which can reach long distances, often more than 100 kilometers. Baleen whales may think that the song may attract the mate. [17] The measuring unit of a sound's loudness under water is decibels and this is not same as dB levels in air. The Blue whale makes sounds of 12-390 Hz at 188 dB, the Gray whale makes sounds in the range of 20-2000 Hz, and the Humpback whale makes sounds in the range of 30-8000 Hz. Each song takes 1-3 minutes and only males sing during the winter season and in the breeding area. When they leave the area they stop singing until the next winter when they start to sing with a similar song. [18]