Dolphins
and Whales
Dolphins
and Whales
Introduction
Dolphins and Whales are both members of a group of mammals called cetaceans. They both live in the sea (mainly because of their weight), but are mammals - they need to go up to the surface of the water to breath! Both dolphins and whales swim using the same technique - using their flukes (tails) for speed, and their fins for directing themselves through the water.
Dolphins
Dolphin families-
Like humans, dolphins are quite social mammals, as you will always see several of them together. These are usually family groups (that includes calves, parents, grandparents and aunties), called "schools". Some schools may join up with other groups, to help each other out. Dolphins are much safer in groups and, if everyone works together, it is easier to catch food.
Females with new calves, are usually found swimming together, while older calves hang out in gangs, and adult males roam around freely.
Mothers and calves-
Female dolphins usually have about 3-4 babies in their lifetime but it is hardly ever the same father.
Did you know that dolphins are pregnant for twelve months, before giving birth in twenty to thirty minutes to a calf - tail first!
Did you know that when a calf is born, its mother whistles several times, to make the baby learn her call to find her when the calf is lost.
Once a calf is born, it sticks close to its mother, so that it is harder for predators to see it!
Dolphin movements-
Dolphins enjoy leaping and twisting high up in the air, splashing and squirting water. Many young dolphins chase one another and find toys to play with.
Sometimes you will see them playing with humans, e.g.- surfing on waves with them!
Underwater dolphins swim quickly, but gracefully through the deep blue sea. They wiggle their way gently through the oceans' currents.
Learning when playing-
It is important for young dolphins to play, as it is quite useful:
Did you know that when dolphins play, they are sometimes great copy-cats, as bottlenose dolphins love impersonating other animals, as once a dolphin was spotted lying on its back with its flippers across its chest - like a slumbering seal!
Boats and dolphins-
Many dolphins enjoy riding in the bow wave at the front of boats and ships. They also love playing in the frothy waves left behind by large boats, or they sometimes will play in the pressure waves created by a humpback whale!
Eating habits-
Many dolphins' favourite food is fish, crab or lobster but they are not that fussy.
There are two families of dolphins; the marine dolphins, and the river dolphins.
Marine Dolphins:
Marine dolphins are what we call the dolphins that live in the oceans. There are about 32 different species of marine dolphins! Here are a few:
Did you know that the various species of dolphins range from 1.4 to 9 m long, and weigh from 45 kilos to 9tonnes!
Bottle-nose dolphins
Bottle-nose dolphins live in tropical waters. Most of them stay within 160kilometers of land. Many live in bays, where the water is relatively shallow. Bottle-nose dolphins range as far north as Japan and Norway, and as far south as Argentina, New Zealand, and South Africa.
Did you know that the bottle-nose dolphin is one of the largest marine dolphins
Common dolphins
Common dolphins live in tropical waters. They often swim in large schools and are frequently found seen in the open ocean. Common dolphins sometimes follow ships for many kilometers and may leap out of the water and turn somersaults.
River dolphins
River dolphins, unlike other cetaceans, usually live in the muddy waters of such rivers as the Amazon in South America, the Ganges in India, the Indus in Pakistan, and the Yangtze in China. They normally measure 1.5 to 2.4 meters and have a long beak. Even though these dolphins have small eyes they can see quite well, but in rivers like the "Amazon river", it is very muddy, so hart to see. Young river dolphins love to play games and try out what they know.
In many countries dolphins are sadly killed just for:
Whales
Whales are mammals, not fish. They live in the sea, but they breathe air and are warm blooded creatures with hair and mammary glands. Young whales are born alive and the largest whale of all is the blue whale.
Some whales have teeth instead of whale bone. Whales with teeth may eat fish such as herring and tuna.
Some kinds of whales are much smaller than blue whales, like belugas
and narwhals,
for example, grow to only about 3 to 5 meters in length.
The life span of whales ranges from 15 years for the common porpoise to 60 or more years for killer, bowhead, and sperm whales. Humans and large sharks are the reason for many whale and dolphin deaths. If whales escape human actions and large predators they die of parasite infections, other diseases or old age.
Scientists have identified at least 75 kinds of whales, and divide the various kinds into two major groups:
Whales live in groups called herds, pods or schools and communicate with one another by making a wide variety of sounds called phonations. The best-known whale sounds are the songs of the humpback whales, and each song consists of a series of sounds that lasts up to 20 minutes and is then repeated.
Whales have no sense of smell, but they have good eyesight and a well-developed sense of taste. They can hear an extremely wide range of sounds, including low and high pitched sounds far beyond the range of human hearing. Whales can also tell from what direction a sound is coming underwater.
The blue whale
The blue whale is the largest mammal that has lived on earth. Its size is longer than a Boeing 737 jet and weighs 25 times more than an African elephant. The blue whale can live about 50 years.
Blue whales can only live in the oceans where the water supports its enormous bulk, but they move like living torpedoes, even though they have such a lot of weight to carry. They are powerful swimmers and swim half way around the globe between their birth grounds and feeding grounds. They swim between cold polar waters and warmer waters - where their calves are born.
They feed on the tiniest plankton and shrimps, and when they have to feed, they swim with their mouth open, collecting organisms in the water. They then close their enormous mouth, squirting water through a fringe of baleen plates, because their food is so small. Whales are constantly swallowing and managing to eat four tons of plankton a day!
Blue whales are friendly mammals and spend most of their time in small pods of three to five other whales. Whales give birth to one calf at a time. A calf weighs two to three tons when they are born and the calf drinks 360 pints of mil a day!
Did you know that whales sing to communicate with each other and they can hear each other from a distance of over 800 kilometers!
Blue whales are rare and were driven to the brink of extinction by whalers who hunted them to their blubber and bone. Conservation efforts have restored numbers to 10,000 animals.
Baleen Whales
There are ten species of baleen whales including the humpback, bowhead and
blue
whale. All of these have a series of horny plates with fringed edges
hanging from the roof of the mouth. These whalebone plates are called
baleen and are used as a sieve for feeding. Baleen whales feed on animal
plankton - krill and tiny creatures that float in the water. Where these
creatures swarm, the whale opens its mouth, takes in sea-water, then pushes it
out through baleen leaving the food in its jaws, kept by the baleen. The
blue whale, the biggest animal that has ever lived, grows to 150 tonnes on the
diet of krill and tiny creatures. A blue whale may gather 4,000,000 of
krill a day!
Killer Whales - (Orcas)
The killer whale (the orca whale) uses its teeth to catch bigger prey than
the baleen whales. Much of a killer whale's diet is fish and squid, but it
is known that this whale will almost attack anything from penguins and sea
lions, to blue whales.
Killer whales, which are dolphins, occasionally attack young whales, smaller dolphins, and weak or diseased baleen whales.
The jet black and shocking white may help to camouflage a killer whale by breaking up its outline. Orcas live in every ocean of the world, and researchers in British Columbia have found two types:
The sperm whale
The head of a sperm whale, is full of an oily, waxy substance, called
spermaceti oil,
this is one of the reasons why sperm whales are killed.
Like the killer whale, the sperm whale is found in all the world's oceans, and a
family of 30 or more females and calves stay together in the waters, around the
world. Many male sperm whales, have scares on their heads, from wars with
giant squid. The lower jaw of a sperm whale contains from about 18 to 28
pairs of teeth.
When sperm whales get together, they often repeat slow patterns of clicks called codas. When one whale produces a particular coda, another whale will repeat it. Sperm whales have the largest brain that ever existed, but it is hard to imagine that they can say a lot in a few simple clicks!
Breathing
When a whale is underwater its blowhole is closed by muscles surrounding the opening. Different species of whale, produce different shapes of spout. Many whales can dive to great depths. A whale also carries oxygen in its muscles as well as its lungs. Like all other mammal, whales have lungs and must come to the surface regularly to breathe. Baleen whales usually breathe every 5 to 15 minutes, but they can go as long as 40 minutes without breathing.
Did you know that a sperm whale can go down to more than 3,000 meters and stay underwater of 1 and a half hours at a time.
Did you know that a whale's lungs are actually smaller than a humans, and while a whale changes 90% of air in its lungs, we only change 12 %.
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