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[19] [20] The male genitals are attached to a vestigial pelvis. [21] The body is wrapped in a thick layer of fat, known as blubber. This provides thermal insulation and gives cetaceans their smooth, streamlined body shape. In larger species, it can reach a thickness up to one-half meter (1.6 feet). [citation needed]
Whales have two flippers on the front, and a tail fin. These flippers contain four digits. Although whales do not possess fully developed hind limbs, some, such as the sperm whale and bowhead whale, possess discrete rudimentary appendages, which may contain feet and digits.
The beluga's body shape is stocky and fusiform (cone-shaped with the point facing backwards), and they frequently have folds of fat, particularly along the ventral surface. [38] Between 40% and 50% of their body weight is fat, which is a higher proportion than for cetaceans that do not inhabit the Arctic, where fat only represents 30% of body ...
Echolocation also allowed toothed whales to dive deeper in search of food, with light no longer necessary for navigation, which opened up new food sources. [27] [49] Toothed whales echolocate by creating a series of clicks emitted at various frequencies. Sound pulses are emitted, reflected off objects, and retrieved through the lower jaw.
Narwhals also have a comparatively high amount of myoglobin in their body, which helps to facilitate deeper dives. [28] It has a dense layer of blubber , around 50 to 100 mm (2.0 to 3.9 in) thick. This fat accounts for a third of the body mass and helps insulate from cold ocean temperatures.
Sperm whales have the largest brain mass of any animal on earth, averaging 8,000 cm 3 (490 in 3) and 7.8 kg (17 lb) in mature males, in comparison to the average human brain which averages 1,450 cm 3 (88 in 3) in mature males. [44] The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. [45]
[51]: 446 The vestigial hind legs are enclosed inside the body. Rorquals need to build speed to feed, and have several adaptions for reducing drag, including a streamlined body; a small dorsal fin, relative to its size; and lack of external ears or hair. The fin whale, the fastest among baleen whales, can travel at 37 kilometers per hour (23 mph).
Beaked whales have several anatomical adaptations to deep diving: large spleens, livers, and body shape. Most cetaceans have small spleens. However, beaked whales have much larger spleens than delphinids, and may have larger livers, as well. These anatomical traits, which are important for filtering blood, could be adaptations to deep diving.