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The family of dolphins consists of 32 different species.

How intelligent are dolphins?

The short answer to this is that we do not know. There is no reliable method to measure intelligence in humans across cultures, so it is not surprising that comparing humans, dolphins, apes, dogs, etc. is impossible. There are some indications of their potential: they are fast learners and can generalize (which is also true of pigs). Also they can learn to understand complicated language-like commands (which is also true of the great apes).

How do dolphins communicate and do they have their own language?

Dolphins communicate mainly by means of sounds. These sounds include whistles, but also so-called pulsed sounds, which are often described as squawks, barks, rasps, etc. But they also use breaching (jumping and falling back into the water with a loud splash) and pectoral fin (or flipper) and tail (or fluke) slaps (hitting the flipper or fluke on the water surface). Body posturing and jaw popping also have a role in communication. This list is not exhaustive. As for language, we do not know if they have one. Several studies have demonstrated that dolphins can understand a structured language like ours. This same has been demonstrated for a number of other animals species as well (gorilla, bonobo, California sea lion, parrot). Some studies also indicate that dolphin vocalizations are complex enough to support some form of language. However, to date it has not been demonstrated yet that they indeed use a language for communication among themselves.

How does dolphin sonar work?

Dolphins (and other toothed whales) can produce high pitched clicks. When these clicks hit an object, some of the sound will echo back to the "sender". By listening to the echo and interpreting the time it took before the echo came back, the dolphin estimate the distance of the object. (That's why sonar is also called echolocation: with information from the echoes, a dolphin can locate an object). Depending on the material the object is made of, part of the sound may penetrate into the object and reflect off internal structure. If the object is a fish, some sound will reflect off the skin on the dolphin's side, some of the bones, the internal organs and the skin on the other side. So one click can result in a number of (weaker) echoes. This will give the dolphin some information about the structure and size of the fish. By moving its head (thereby aiming the clicks at other parts of the fish) the dolphin can get more information on other parts of the fish. It is like a medical ultrasound probe, but the results are far less clear. A medical probe moves back and forth very rapidly, much faster than a dolphin can move its head. Also the frequency of the sounds of the medical probe is much higher than a dolphin's sonar. Therefore the level of detail the echoes can provide is much higher in the medical probe.

What and how much do dolphins eat?

Bottlenose dolphins eat several kinds of fish (including mullet, mackerel, herring, cod) and squid. The composition of the diet depends very much on what is available in the area they live in and also on the season. The amount of fish they eat depends on the fish species they are feeding on: mackerel and herring have a very high fat content and consequently have a high caloric value, whereas squid has a very low caloric value, so to get the same energy intake (calories) they will need to eat much more if they feed on squid than if they feed on mackerel or herring. On average an adult dolphin will eat 4-9% of its body weight in fish, so a 250 kg (550 lb) dolphin will eat 10-22.5 kg (22-50 lb) fish per day.

Photo by Martin Allen

Do dolphins live shorter in captivity?

No. A recent study, comparing the survival of dolphins in captivity from 1940 through 1992 showed no significant difference in ASR between the "captive population" and the Sarasota Bay population. The ASR for the captive population was 0.944 (life expectancy: 17.4 years). Also in captivity dolphins have reached ages over 40 years. 

Where can you find dolphins?

Whales and dolphins can be found in almost every sea and ocean, from the Arctic ocean, through the tropics all the way to the Antarctic. Each species however has its own preferred type of habitat. Some live cold water only, others in tropical oceans only. There are also species that can be found in a large variety of environments, like the bottlenose dolphins, killer whales and sperm whales.

How do dolphins get their water?

Most dolphins live in the ocean and the ocean water is too salty for them to drink. If they would drink sea water, they would actually use more water trying to get rid of the salt than they drank in the first place. Most of their water they get from their food (fish and squid). Also, when they metabolise (burn) their fat, water is released in the process. Their kidneys are also adapted to retaining as much water as possible. Although they live in water, they have live as desert animals, since they have no direct source of drinkable water.

Photo by Martin Allen

Are whales and dolphins endangered?

For most species, the answer is probably "No", although it is very difficult to get a good estimate of the size of populations on these water living creatures. A number of species are endangered: the Indus river dolphin, the baiji (there are only about 100 left), the vaquita, the northern right whale and the blue whale. Another group of species is listed as "vulnerable" (which means that they are not in immediate danger of extinction, but also far from safe). These are: the Ganges river dolphin, the boto, the bowhead, the southern right whale, the sei whale, the fin whale and the humpback whale.

How do dolphins sleep?

Dolphins have to be conscious to breath. This means that they cannot go into a full deep sleep, because then they would suffocate. Dolphins have "solved" that by letting one half of their brain sleep at a time. They can either: - swim slowly and surface every now and then for a breath - rest at the surface with their blowhole exposed - rest on the bottom (in shallow water) and rise to the surface every now and then to breath.

Can newborn dolphins swim?

Newborn dolphins 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! Calf's also have to interrupt their swims for them to suckle milk from their mothers mammary glands, these are slits either side of the genital opening underneath her. Suckling takes place either stationary or on the move. Dolphin milk is squirted directly into the calf's mouth and their tongues have a frilled margin to make a seal. Dolphin milk is extremely rich and contains up to ten times the fat and protein found in land mammals milk.

Who is the fastest of them all?

The fastest cetacean is the killer whale (orca), which can swim at speeds of up to 60km/h (40mph). This is over seven times quicker than the speediest human swimmer. The killer whale can swim the same speed as Flying fish but the fastest fish is the Sailfish which can swim up to 100km (60mph).

Photo by Martin Allen

Did you know.........?

The blue whale's tongue weighs as much as an african elephant

The temperature of a whale is about the same as a human

Dolphins pick up sounds through their lower jaw

Male whales will help injured female whales but females rarely help injured males

Female sperm whales can mate at the age of 8,male sperm whales cannot mate until they are nearly 20

Whales that get stranded in Britain belong to the monarch

Humpback whales can live to 95

The first whale sanctuary was set up in 1945

The sperm whale can stay underwater for an hour after surfacing for air

The dorsal fin of a fully grown male orca can be as tall as 6ft

When a blue whale is born it is 23 ft long and drinks 65 gallons of milk from its mother each day

Bottlenose dolphins have around 300 teeth

As well as sonar, clicks and squeaks, dolphins communicate by acrobatic leaps

Large whales are much bigger than elephants, yet they are pregnant for a shorter time, minke whales are pregnant for 10 months and an elephant is 20 months. This is partly to do with the yearly migrations of some whales

Dolphins have the sense of taste but not smell

Dolphins don't need to resurface for air for 5 to 8 minutes at a time

Dolphins closest land relatives are thought to be cows, pigs & deer


Bottlenose Dolphins

Family: Delphinidae

Species: Tursiops truncatus

Birth weight: 15-30kg (35-65Ib)

Adult weight: 150-650kg (330-1435Ib)

Group sizes

Inshore: 1-10    Offshore: 1-25 (up to 500 may occur offshore)

Other names for Bottlenose Dolphins

Grey Porpoise, Black Porpoise, Atlantic (or Pacific) Bottlenose Dolphin, Cowfish

Locations to be found

Black Sea, Red Sea, Mediterranean Seas, Gulf of California, Mexico & the open sea in the eastern tropical Pacific

Diet

Fish, squid, krill & crustaceans

Threats

Hunting, entanglement in fishing nets, pollution, human disturbance


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