Dolphins are sometimes confused with porpoises (Phocoenidae), but the main difference between the two is the dolphin has a beak-like snout and a curved dorsal fin, whereas the porpoise’s head is blunt and its dorsal fin is triangular. Dolphins are mammals, as they have lungs and breath air. In all, there are 79 different kinds of whales, dolphins and porpoises, of which there are 26 types of ocean dolphins and 5 river dolphins.
Dolphins are actually a species of whale, coming under the order of Cetacea, with many people failing to see them in the Odontoceti sub-order.
Classified in the family of Delphinidae, dolphins are in the “Rough Toothed Whale” class due to their conical teeth, and lack of fingernail-like substance that grows from the upper jaws.
Dolphins have a thick layer of fat called blubber that protects them from the cold temperatures of the icy waters. Those that live in colder waters usually have a thicker blubber than those that live in warmer waters.
Gestation for dolphins is about 12 months for a Bottlenose Dolphin, with the young carried in the womb during this time. During birth, the baby emerges tail first and will suckle from its mother for up to four years.
The skin of a dolphin has a rubbery feel to it and it is also hairless, so as they swim through the water the resistance is reduced. But the skin is also very sensitive as, unlike humans, its outer layer is made up entirely of live cells and therefore has no protection to bumps or bruises.
The most frequently encountered species in the equatorial waters of the Pacific are the Common or White-bellied dolphin and the Bottle-nosed dolphin. The Common dolphin (Delphinus delphis) can be found in all temperate and tropical seas. It can be up to 2.5m (that’s 8ft) in length and is dark above, white below, with bands of grey, white and yellow on the sides.
Dolphins can be found in many parts of the world in various oceans and even in the freshwater rivers of Asia, Africa and South America. There are only five species of river dolphins and they all belong to the family Platanistidae. All river dolphins are in danger of extinction due to pollution and dams, and because of this the Whitefin or baiji dolphin Lipotes vexillier of the Chang Jiang River in China is the world’s rarest cetacean. There were only an estimated 300 remaining in the early 1990’s but in 1995 it was feared that there were less than 100.
Every dolphin has its own signature whistle to distinguish it from other dolphins, much like a human fingerprint
The gender differences between a male and female dolphin are only noticeable close-up, with the female having a mammary slit (for birth) on the underside.
Deep within a dolphin’s body it’s temperature is normally 35 degrees to 36.9 degrees, while it’s outer body temperature is usually cooler. In comparison, man’s body temperature is 37.3 degrees
Dolphins usually live up to about twenty years, but have been known to live for about forty.
Dolphins sleep in a semi-alert state by resting one side of their brain at a time
Dolphins can help other sick or injured dolphins as often as they can, and they work as team if danger is nearby
A dolphin can hold its breath for 5 to 8 minutes at a time
Dolphins closest land relatives are thought to be cows, pigs and deer .
Common Dolphin Terms
POD: A group of dolphins that swim, hunt and play together
ROSTRUM: A dolphin’s snout. It is made up of a very hard material and is used for digging and attacking enemies
BLUBBER: Fatty tissue belo a dolphin’s skin to help keep it warm
CALF: A calf is a baby dolphin
DORSAL FIN: Found on a dolphin’s back and is used for balance in the water
BLOWHOLE: This is a hole at the top of a dolphin’s head, used for breathing and making sounds
FLUKES: These are fins on the dolphin’s tail that flap up & down to drive the dolphin through the water
MELON: This is the dolphin’s forehead. It gained its name due to the shape
PECTORAL FINS: The fins located on either side of the dolphin. They are used for steering and stopping
ECHOLOCATION: A dolphin’s sonar, clicks that emit through the dolphin’s melon and return an echo that is retrieved through the lower jaw. Dolphins can determine the size, shape, speed, density and materials of an object through echolocation