What are dolphins?
Dolphins are small, toothed whales. They belong to the group known as cetaceans (from the Latin word cetus, meaning large sea animal) which includes all whales, dolphins, and porpoises.
How many species are there?
There are many different kinds of dolphins, around thirty or forty species of dolphins, including some species we would commonly call whales, such as orcas and pilot whales. Bottlenose dolphins (Tursiops truncatus) are one of the most wide-ranging species. They live along tropical and temperate coasts all around the world. Other species of dolphins live in cold waters, such as the Atlantic white-sided dolphin that can be seen from the Gulf of St.Lawrence to the North Sea, and the hourglass dolphin that lives in the waters of the Antarctic.
How are dolphins like us?
Dolphins and humans have a lot of things in common. First of all we are both mammals. We nurse our young, which are born alive, not hatched from eggs. Mammals breathe air. A dolphin must come up to the surface to breathe through a blowhole on the top of its head. When it dives, the blowhole closes shut. Rather than breathing continuously, like we do, a dolphin takes a breath and holds it until it surfaces again. Unlike us, dolphins breathing is not automatic, so they have to think to breathe rather than think to hold their breath.
Both humans and dolphins are warm-blooded. A dolphin's body temperature is normally 96-98.6 degrees Fahrenheit. Its outer body temperature is slightly lower. A human's body temperature is 98.6 degrees Fahrenheit just a fraction higher than a dolphin's.
How do dolphins communicate?
Dolphins communicate by making two types of sounds: vocalizations and echolocation. Vocalizations are the many noises dolphins use to communicate. These sounds come from their blowholes. Echolocation, also called sonar, is the way dolphins locate and distinguish between objects underwater. A dolphin emitts a sound and listens for the echo. This allows a dolphin to navigate through dark or murky water without bumping into anything. A dolphin produces powerful clicking sounds that travel through the water, which then bounce off objects and return to the dolphin. A whopping 1,200 clicks a second can be transmitted ahead of a dolphin like a beacon. These clicks come from the rounded forehead of the dolphin, called the melon. This melon along with the lower jaw are filled with a jelly-like substance used to smplifie sound waves. Therefore, as a dolphin swims, it moves its head back and forth to scan its surroundings, while the echos it sends out bounce off objects and hit the lower jawbone, which conducts the returning sound waves to the inner ear. By the pitch of the returning echo and the time it takes to get there, the dolphin can determine the shape, size, speed, texture, and density of the object. It can even view the inside of an object, almost like an X-ray, except it a dolphin has vision by sound.
How many kinds of dolphins are there?
There are over 33 different species of dolphins, over 5 different species of river dolphins, and over 6 different species of porpoise.
Ocean Dolphins: Atlantic White-sided Dolphin, Atlantic Borneo White Dolphin, Bottlenose Dolphin, Borneo White Dolphin, Bouto Dolphin, Broad-beaked Dolphin, Cameroon Dolphin, Chinese White Dolphin, Clymene Dolphin, Commerson's Dolphin, Common Dolphin, Dusky Dolphin, Falkland Island Dolphin, Fraser's Dolphin, Heaviside's Dolphin, Hector's Dolphin, Hour-glass Dolphin, Long-snouted Spinner Dolphin, Northern Right Whale Dolphin, Pantropical Spotted Dolphin, Peale's Dolphin, Plumbeous Dolphin, Rio de Janeiro Dolphin, Risso's Dolphin, Rough Toothed Dolphin, Southern Right Whale Dolphin, Speckled Dolphin, Spinner Dolphin, Spotted Dolphin, Striped Dolphin, White- beaked Dolphin,White-bellied Dolphin, White-sided Dolphin.
River Dolphins: Amazon River Dolphin, Baiji Dolphin, Indus River Dolphin, Ganges River Dolphin and Guiana River Dolphin.
Porpoises: Black Porpoise, Black Finless Porpoise, Cochito, Dall's Porpoise, Finless Porpoise, Harbor Porpoise, Spectacled Porpoise, True's Porpoise.
.jpg) Dolphins are part of the Delphinidae family, which
contain various highly intelligent aquatic mammals. The name Dolphin refers to the species
that have a beaklike snout and slender, streamlined body, which has developed over
millions of years through evolution to enable them to swim at high speeds. You should also
remember that dolphins are mammals and not fish as they breath using lungs and not gills,
and they also give live birth as opposed to laying eggs.
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. ...that some species of dolphin can swim at speeds
up to 56 kmh All dolphins use their flukes to drive them through the water by beating them up and down. Their pectoral fins are simply used to steer and stabilize them. ...that Man has studied the flukes on a dolphin's tail to improve the effectiveness of submarines and boat propellers. Their feeding behaviour is incredibly varied, it simply depends on what is available. A general meal would consist of small fish or squid.
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. 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. ...that dolphins have teeth? Well they do! They are used for grabbing food, not chewing it as dolphins swallow fish whole
The second species that I have already mentioned is the Bottle-nosed dolphin (Tursiops truncatus). It is this type of dolphin that is the most frequently seen as it can be found in all warm seas. Also the Bottle-nose is the most studied and best known species of dolphin. They are mainly grey in colour and can grow to a maximum of 4.2m (that's 14ft) in length and can weigh 205kg (yup, that's 450lbs). When they live in costal areas they tend to be in fairly open groups of no more than 20 animals, but when they are offshore they have been seen in large hoards. Here are some other dolphin facts that you may find
interesting... |
| Blowhole | This is a hole at the top of a dolphin's head, used for breathing and making sounds |
| Blubber | This is the fatty tissue below a dolphin's skin to help it keep warm |
| Calf | A calf is a baby dolphin |
| Dorsal fin | This is found on a dolphin's back, and it is used for balance in the water |
| 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 |
| 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 the name due to its shape. It contains a fatty substance and it is used for echolocation |
| Pectoral Fins | The fins located on either side of the dolphin. They are used for steering and stopping. |
| Pod | A group of dolphins that swim, hunt & play together |
| Rostrum | The dolphin's snout. It is made of a very hard material and is used for digging and attacking enemies |
.jpg)
Dolphins do not have the
best eyesight in the world but they do reply on echolocation to navigate, find food and
communicate. Echolocation is a technique that dolphins use to 'see' what is ahead of them
by the use of sounds. These sounds, or clicks, are produced by a mechanism just below the
blowhole and are emitted at a rate of about 300 sounds a second. When these sound waves
hit an object, the echo bounces back and the dolphin then knows that something lies ahead.
The signature whistles, or squeals, that are used by dolphins are for communication and as
a way of indicating their emotional states. .jpg)
The Common dolphin, like
the Bottle-nosed dolphin, has up to 26 teeth in its each side of its jaws (that's a
possible total of 104 teeth!), which make the 'beak' protrude forward from the well
rounded head. The previously mentioned beak can be 15cm (6in) in length, and as we all
know, it is not the dolphins nose. They breath by just surfacing, as opposed to sticking
their whole head out of the water, and using their blowholes. You could say that blowholes
are the equivalent of the human nostrils. The first thing a newborn dolphin must do is to
go to the surface to breathe. But the newborn can not swim so its mother and a another
dolphin will help push it to the surface for its first breath of air. The calf is a quick
learner though, as it will be able to swim in about 30 minutes!