Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial, or Four-Legged, Vertebrates — Amniotes
Class Mammals — Subclass Theria — Suborder Baleen Whales

Baleen whales, or mysticetes, are characterized by the absence of Teeth and the presence of keratinous plates lining the sides of the palate to form a straining apparatus. These plates are commonly known as whalebone, or baleen. Most species feed on planktonic invertebrates and, less frequently, on small fish. Distributed across all oceans, they are most abundant in temperate and cold waters and undertake regular Migrations. In the Northern Hemisphere, whales spend the winter in tropical waters, moving northward in the summer when plankton blooms abundantly. In the autumn, they migrate back to the south. Similar migratory patterns are observed in the Southern Hemisphere.

Most whales are large in size. The blue whale (Balaenoptera musculus) reaches up to 30 m in length and weighs about 150 t (see Fig. 202, 2). Its Stomach can hold 1.5 t of crustaceans. It typically gives birth to a single calf after an 11-month gestation period. The newborn is 6 — 9 m long and weighs 2 — 3 t. Over a 7-month Lactation period, the calf grows to 16 m and reaches a mass of about 23 t. Although distributed throughout the World Ocean, its population size is currently very low. The situation is particularly critical for the North Atlantic population, which numbers no more than 100 — 150 individuals. This subspecies is listed on the IUCN Red List and the Red Data Book of Russia.

Whale populations have been devastated by overexploitation; as early as the 17th and 18th centuries, the harvest of the bowhead whale (Balaena mysticetus) dropped sharply. In the 19th and 20th centuries, its numbers declined to such an extent that the population broke up into isolated herds. The species is on the brink of extinction and is listed on the IUCN Red List and the Red Data Book of Russia.

The total population of other whale species continues to decline. In the 1960s and 1970s, most nations ceased commercial whaling. The Red Data Book of Russia includes 16 cetacean species.