Dolphin Physiology

Dolphins may live in the ocean, but they’re mammals that are fully adapted to live in water.

There are a number of adaptations that dolphins developed during evolution living in water instead of on land. For instance, dolphins and other cetaceans have no hair whatsoever, with the exception of a few follicles on their lower jaws and snouts.

Dolphin Senses

Probably one of the most important difference between land mammals and dolphins is the way they vocalize.

While most mammals have a larynx or a similar structure that allows them to vocalize using throat vibrations and exhaled air. Dolphins and other cetaceans are no different; but they’re specially adapted to make extremely high-pitched sounds used for echolocation as well as more human-pitched sounds used for ordinary communication with others in their pod.

In addition, dolphins have extremely sharp hearing, and much better vision than one might expect of an animal that uses echolocation as its primary means of sensing the world. Dolphins can see limited colors, and even have limited binocular vision like a primate. They do not possess much of a sense of smell, however.

Dolphin Swimming

One of the most interesting differences between cetaceans and fish is in their swimming method. Fish swim by wiggling left and right, and if you watch crocodiles and snakes you’ll see the same motion. But because dolphins were descended from mammals with a quite different skeletal structure, they use up and down strokes to swim.

Today you can still see some of the remnants of terrestrial mammals in the dolphin’s skeletal structure. For instance, they have forelimbs, but they’re adapted into flippers with shortened arm bones and no fingers. Hind limbs can sometimes be found as vestigial skeletal remains, much like tails can still be found vestigially on some humans. Most cetaceans, including dolphins, still have a pelvis, which is entirely absent from fish.

Unlike other mammals, a dolphin’s hind quarters are much, much more developed than its front musculature; the flippers are only to steer, while the tail provides most of the force of motion. Dolphins have also developed horizontal flukes on their tail to make propulsion more efficient, and they’ve developed a dorsal fin just like fish. External parts that get in the way of a dolphin’s streamlined shape, like the genitalia or the ears, have been entirely lost, turning into internal organs instead.

Dolphin senses.

Blowhole.

Breathing

Dolphins, like other mammals, breathe air instead of water, and thus use lungs instead of gills. A dolphin that cannot surface also cannot breathe, and thus will drown; this is why dolphins caught in fishing nets are given such a poor chance of survival. Unlike most fish, dolphins are very much creatures of the surface of the ocean.

Like whales and other cetaceans, dolphins respire through a blowhole in the tops of their heads, breathing in air when they break the surface of the water. Unlike humans, dolphins do not breathe reflexively; instead, they have to remember to breathe. An unconscious dolphin is likely to be a dead dolphin. Though when actively swimming they must breathe fairly often, dolphins can hold their breath for fifteen minutes or more.

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