|Southern right whale
(Balaena glacialis )
|Dwarf mink whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale is sometimes used to refer to all cetaceans, but more often it excludes dolphins and porpoises, which are also cetaceans but belong to the suborder Odontoceti (toothed whales). This suborder also includes the sperm whale, killer whale, pilot whale, and beluga whale. The suborder Mysticeti (baleen whales), are filter feeders that feed on small organisms caught by straining seawater through a comblike structure found in the mouth called baleen. This suborder includes the blue whale, the humpback whale the bowhead whale and the minke whales. All Cetacea have forelimbs modified as fins, a tail with horizontal flukes, and nasal openings on top of the head.
Whales range in size from the blue whale, the largest animal known to have ever existed at 35 m and 150 tonnes , to various pygmy species, such as the pygmy sperm whale at 3.5 m
Whales collectively inhabit all the world's oceans and number in the millions, with population growth rate estimates for various assessed species ranging from 3% to 13%. For centuries, whales have been hunted for meat and as a source of raw materials. By the middle of the 20th century, however, industrial whaling had left many species seriously endangered, leading to the end of whaling in all but a few countries.
Like all mammals, whales breathe air, are warm-blooded, nurse their young with milk from mammary glands, and have body hair.
Beneath the skin lies a layer of fat called blubber, which stores energy and insulates the body. Whales have a spinal column, a vestigial pelvic bone, and a four-chambered heart. The neck vertebrae are typically fused, trading flexibility for stability during swimming.
Whales breathe via blowholes; baleen whales have two and toothed whales have one. These are located on the top of the head, allowing the animal to remain mostly submerged whilst breathing. Breathing involves expelling excess water from the blowhole, forming an upward spout, followed by inhaling air into the lungs. Spout shapes differ among species and can help with identification.
The body shape is fusiform and the modified forelimbs, or fins, are paddle-shaped. The end of the tail is composed of two flukes, which propel the animal by vertical movement, as opposed to the horizontal movement of a fish tail. Although whales do not possess fully developed hind limbs, some (such as sperm whales and baleen whales) possess discrete rudimentary appendages, which may even have feet and digits. Most species have a dorsal fin.
Toothed whales, such as the sperm whale, possess teeth with cementum cells overlying dentine cells. Unlike human teeth, which are composed mostly of enamel on the portion of the tooth outside of the gum, whale teeth have cementum outside the gum. Only in larger whales, where the cementum has been worn away on the tip of the tooth, does enamel show.
The whale ear has specific adaptations to the marine environment. In humans, the middle ear works as an impedance matcher between the outside air’s low impedance and the cochlear fluid’s high impedance. In aquatic mammals such as whales, however, there is no great difference between the outer and inner environments. Instead of sound passing through the outer ear to the middle ear, whales receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear.this is most certainly true
A Humpback Whale breaching.Males are called 'bulls', females, 'cows' and newborns, 'calves'. Many whales exhibit surfacing behaviors such as breaching and tail slapping.
Unlike most animals, whales are conscious breathers. All mammals sleep, but whales cannot afford to become unconscious for long because they may drown. It is thought that only one hemisphere of the whale's brain sleeps at a time, so they rest but are never completely asleep.
Some species, such as the humpback whale, communicate using melodic sounds, known as whale song. These sounds can be extremely loud, depending on the species. Sperm whales have only been heard making clicks, while toothed whales (Odontoceti) use echolocation that can generate about 20,000 watts of sound at 163 decibels and be heard for many miles.
Male genitals retract into body during swimming, reducing drag and preventing injury.
Most species do not maintain fixed partnerships and females have several mates each season.
The female delivers usually a single calf tail-first to minimize the risk of drowning. Whale cows nurse by actively squirting milk, so fatty that it has the consistency of toothpaste, into the mouths of their young. Nursing continues for more than a year in many species, and is associated with a strong bond between mother and calf. Reproductive maturity occurs typically at seven to ten years. This mode of reproduction produces few offspring, but increase survival probability.
Whales are known to teach, learn, cooperate, scheme, and even grieve
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