All About Dolphins

From http://www.southwest.com.au/~kirbyhs/dolphinsa.html

By Sally Kirby

Dolphins are mammals, not fish. They are warm blooded like man, and give birth to one baby called a calf at a time. At birth a bottlenose dolphin calf is about 90-130 cms long and will grow to approx. 4 metres, living up to 40 years. They are highly sociable animals, living in pods which are fairly fluid, with dolphins from other pods interacting with each other from time to time.

Dolphins use their powerful tail flukes in an up and down motion to move through the water. They also use their tails when hunting, hitting a fleeing fish up into the air with their tail, stunning it, then scooping the fish up when it falls back into the water. A dolphin slapping its tail on the water in the wild may be a sign of annoyance, or a warning to other dolphins of danger.

Their pectoral flippers are used to steer them through the water, and they also use them to stroke one another, increasing the social bond between them. Dolphin "friends" may swim along face to face touching flippers. Dolphins that appear to be closely bonded may swim in synchrony, twisting, turning and swimming in perfect harmony together.

Their teeth are interlocking rows of conical pegs, suitable for holding slippery fish. They eat their fish whole, headfirst. In the wild an open mouth is a sign of aggression, as is head nodding. A sign of greater aggression is violent jaw clapping.

Dolphins breathe through their blowhole located at the top of their head. A dolphin may empty and refill its lungs in less than a fifth of a second. As the dolphin breathes the air leaves the blowhole at speeds of over 100mph. Complex nerve endings around the blowhole sense pressure changes so the dolphin knows exactly when the blowhole is in or nearing the air and can be opened. Water in a dolphin's blowhole will actually drown it so powerful muscles close the blowhole as it dives under the water again.

The dolphin's eyes produce a special slippery secretion, which protects the eyes from foreign objects and water friction. To sleep, a dolphin must shut down only half of its brain, as its breathing is under voluntary control. Dolphins take short catnaps, floating just below the surface, then slowly rising to breathe. Often dolphins are very active during nighttime, for some this is their main feeding time.

The dolphin's skin is completely smooth allowing the dolphin to move easily through the water, and also reduce heat loss. Their skin may bear rake marks from other dolphin’s teeth during play or mating, and can easily become badly sunburnt if they strand. Their bodies are very streamlined so they may swim at high speeds through the water, and an example of this is their ears. Dolphin's ears are barely noticeable marked only by a small hole just behind the eye. In a bottlenose dolphin the ear is about 5-6 cms behind the eye and only 2-3 mm in diameter.

Dolphins are able to dive to great depths, and also leap to great heights. They may leap to avoid predators or to show how powerful they are to females at mating time. Noisy splashing jumps may also be used to herd fish. Bottlenose dolphins can dive to depths of over 1,640 ft (500m).


The life of a dolphin

Dolphins carry their young inside their womb and gestation is about 12 months for a bottlenose. The baby emerges tail first, and will suckle from its mother for up to 4 years (a calf may stop suckling sooner depending on circumstances).

The baby will however stay with its mother for between 3-6 years, during which time it learns all about feeding techniques, social interaction and group foraging. Females are likely to stay within the family pod with their mother and sisters, though males will leave and form associations with other males. Dolphins have defined home ranges, an area in which they will roam and feed. Though dolphins live in small groups called pods, these pods can be quite fluid and dolphins can be seen interacting with dolphins from other pods from time to time. If another dolphin is drowning, other dolphins will come to its aid, supporting it with their bodies so it's blowhole is above the water allowing it to breathe. Dolphins’ main predators are sharks and unfortunately man, through direct killing for food, netting, pollution, and fishing. Dolphins spend a large part of their day looking for food, or actually feeding. They may either hunt alone, or together as a pod. They use their echolocation (sonar system) to locate fish by sending out a stream of pulses and clicks. Dolphins communicate with each other by whistling or body language. When a baby is first born, some dolphin research suggests a mother dolphin will whistle to it constantly, imprinting her sound on the baby so it will recognize her, and the baby learns to develop its own signature whistle. It is thought that each dolphin has its own individual signature whistle, just like a name.


The past

We all love to see dolphins and for many people the only way in the past to do this was by visiting an aquarium. However aquariums varied in their care and housing of the dolphins in the past, and some may have been quite substandard. And tragically, in the past many of these dolphins were mostly violently captured from the wild, taken away from their families and forced to live in small barren tanks. Records show that at least 2700 bottlenose dolphins have been taken into captivity worldwide. Statistics I have read (from Dolphin Project Europe) say that 53% of captive dolphins who survived the violent capture died within 90 days. And that half of all captured dolphins died within their first two years of captivity. Those that did survive longer lasted an average of only 5 years. Every seven years, half of all dolphins in captivity used to die from capture shock, pneumonia, intestinal disease, ulcers, chlorine poisoning, and other stress-related illnesses. Thankfully a number of countries have now stopped or reduced the capture of wild dolphins and knowledge and conditions are vastly improving but not everywhere. There are still many countries where conditions for captive dolphins are well below standard. You may be shocked to hear that there may still be traveling road shows involving hauling dolphins and sea lions around from city to city in lesser developed countries, or of a dolphinarium open to the public during the daytime, while at night a discotheque with loud thumping music. These are just two examples, in less developed countries particularly there may be many more.

"When a thing exists which you really abhor, I wish you would remember a little whether in letting it strictly alone are you minding your own business on principle, or simply because it is comfortable to do so".
Quote by John Galsworthy.

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