Whales are a diverse group of marine mammals of the infraorder Cetacea. The term whale can refer to any member of the infraorder, including dolphins and porpoises. Whales range in size from the blue whale—the largest animal known to have ever lived—to various pygmy species, such as the pygmy sperm whale and dwarf minke whale. Most whales feed on krill, squid, fish, and other small marine life, but there are some exceptions; the sperm whale feeds on giant squid, while baleen whales filter seawater for their tiny prey using comb-like structures called baleen plates.
Baleen whales include the largest animals on Earth, with the blue whale reaching up to 30 m (98 ft) in length and 170 metric tons (190 short tons) or more in weight. Blue whales were once abundant in all the world’s oceans but have been hunted nearly to extinction by whalers; as of 2016 only about 10% of their original population remained. Other large baleen whales include the fin whale (up to 27 m or 90 ft long), sei whale (up to 26 m or 85 ft), Bryde’s whale (up to 25 m or 82 ft), and minke whale (up to 9 m or 30 ft). Baleen is a keratinous material similar to human fingernails that hangs down from the upper jawbones of certain Mysticetes; it is used by these filter-feeding animals to strain small organisms out of seawater. The primary use for baleen among commercial whalers was for making ladies’ corsets stiffer; it was also used in buggy whips and other products before being replaced by more modern materials such as steel and plastic.
Rorquals are a family of large baleen whales that includes the blue whale as well as smaller members such as Bryde’s Whale, Fin Whale , Humpback Whale , Minke Whale , Sei Whale . These animals are characterized by having pleated throats which allows them expand greatly when feeding . Rorquals use this ability gulp huge amounts water then push it out through their teeth sieve small crustaceans zooplankton .
The Spermaceti organ present only male sperm whales may hold clue how they achieve great depths dives . This large sac found forehead filled with waxy substance believed help creature change its buoyancy so can sink rapidly great depths reach food source squid bottom ocean floor .
Most popular theory suggests light goes dim underwater triggers hormone release causes fatty tissue around organ fill sac make animal float back surface however study published 2012 showed no significant relationship between depth light level changes hormone levels suggesting another mechanism involved regulate oil flow into cavity .