Toothed whales and dolphins are mammals that live in the sea. They may look like large fish, but, like other mammals, they breathe air, have warm blood and give birth to live young that resemble the parents and which are fed on milk by their mothers. The ancestors of the toothed whales were land mammals that went back to the water millions of years ago. They adapted to water so well that they now spend their entire lives at sea. Their front legs have turned into flippers and their back legs have been lost completely. Their tails have become broad and flattened for swimming and they have lost all of their fur. The dolphins are the best known group of toothed whales . Others in the group include the mighty sperm whale made famous in the story "Moby Dick". All toothed whales breathe air through a single blow hole in the top of their heads. Some can dive very deep after prey. They are found all over the world from the tropics to the poles. Some live in shallow coastal areas, some up rivers, and others in the deep oceans. All of them have a special ability called "echo location" which enables them to find food using sound. Some are thought to be very intelligent.
Sylvia Annie Adam
Group size range:
1.5m - 11m.
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|Other names these organisms are known as:
dolphins, porpoises, sperm whales and killer whales.
|What do they look like?
Most toothed whales look like very large fish except that they do not have any scales, have a single blow hole on the top of their heads for breathing air, and have a horizontal instead of vertical tail. Many species have a large dorsal fin in the middle of their backs. Their bodies are very streamlined and most do not have necks, their heads merging with their bodies. Most are grey to black, their bellies usually lighter in colour than their backs and often lightly spotted. Many of the dolphins and smaller toothed whales have a long muzzle or 'rostrum'. All have teeth, although, in some they stay buried in the gums while in others they can have strange shapes. Most, though, have many small pointed teeth for catching fish and squid. Their backs are often covered in pale scars caused by injuries from other whales or sharks or fishing nets. Usually they are seen in groups or 'pods' from a few to several hundred individuals. The young look like miniature versions of their parents and can swim as soon as they are born. The sperm whale looks a bit different to the others as it is much larger and has an enormous square head with a very long narrow lower jaw.
|Where do they live?
The toothed whales can be found in almost every ocean and sea in the world. Some prefer the tropics, others the poles, and others can be found almost anywhere. Some live entirely up rivers. Others live in shallow coastal waters, in bays and around rocky headlands. Some live in amongst the ice floes at the poles. Larger members of the group tend to live in the deeper waters of the oceans. Most tend to only make comparatively shallow dives in search of food. The exception is the sperm whale which can dive to 3200m for up to 2 hours, where it hunts and eats giant squid. Most species do not seem to be territorial, wandering over large areas or great distances along coastlines. They usually live in small groups, or 'pods', although, especially with some species of dolphin, large groups of several hundred animals may occur. Little is known of migratory patterns in these animals.
|How and what do they eat?
Toothed whales differ from their cousins, the baleen whales, in that they chase and eat individual prey. Fish form the basic diet of all toothed whales, but some eat squid as well. To do this, all members of the group are fast and agile swimmers. Most have many small pointed teeth for holding onto slippery prey. The sperm whale, the largest member of the group, will dive to great depths for up to 2 hours to hunt giant squid. Killer whales (which are really large dolphins) are fierce hunters and will eat penguins, seals and even other whales, as well as fish. All toothed whales probably use 'echo location' to find food. This is like a sonar system where the whales make a clicking sound which bounces off their prey and back to the whale. From this reflected sound, the toothed whales can determine the size and the location of the prey. Some blind river dolphins depend on this 'sixth sense' entirely. Some researchers thinks the clicking sounds the whales make may be able to be focused into a beam, and in large whales this beam may be so strong that it may also be able to stun prey as well as find them.
|What eats them?
Toothed whales have few predators. The smaller members of the group may be hunted by sharks but are generally able to escape from them by being fast and agile or can defend themselves in groups. There have even been reports of dolphins ramming sharks in the belly in order to defend other members of their pod. The only other real predator of most toothed whales is itself a member of the group - the killer whale or 'orca'. Killer whales are considered by many to be the greatest predators in the oceans and have no natural enemies. At times they have even been seen attacking large baleen whales such as the blue whale. Apart from these natural enemies, the biggest killers of toothed whales are people.
|How do they grow and reproduce?
Toothed whales spend their entire lives in the water and so mate and give birth in the seas. Many members of the group do not seem to have a seasonal pattern of breeding and may breed at any time of the year, but with peaks of activity at various times. Gestation for most members is between 10 and16 months. Unlike most mammals, when toothed whales give birth, the 'calf' comes out tail first or 'breech'. The new born whale must then get quickly to the surface for its first breathe and is often helped by a 'nurse' whale accompanying the mother. The young are able to swim strongly almost immediately after birth. They are nursed by their mothers, feeding on milk from her mammary glands for up to two years before being entirely independent .The life span of most members is probably around 25 years, although the sperm whale may live to 50 years or more.
|Who do they live with?
The toothed whales usually live in small groups known as 'pods'. These are generally loose family groups like tribes. However, some species will form huge groups of several hundred animals. Others may spend most of their lives being solitary, forming small groups only during the breeding season. Sometimes they are seen mixing with their larger cousins, the baleen whales, and dolphins have even been seen 'bow-riding' on the front of some whales. They have their own species of parasites that live both internally and externally.
|Their connection with people.
Most toothed whales are considered harmless, even friendly by some people. There are several places in the world where wild but curious dolphins have learnt to interact with people. Many dolphins and even some larger toothed whales like pilot whales and killer whales are kept in captivity around the world where they learn to perform spectacular tricks. These captive whales have also been studied intensively and some scientists believe that they may have a very rudimentary language. Unfortunately, however, the majority of our interactions with toothed whales are destructive. Hundreds of thousands of toothed whales, particularly dolphins, die each year as a result of the activities of the world's fishing industries. Many are caught in nets and drown, others are killed by fishermen that think dolphins are eating their fish. Commercial killing of dolphins is practiced in some parts of the world. Sperm whales, the largest members of the group, were once the prime target of the whaling industry, 'spermaceti' and 'ambergris' from their carcasses being worth a great deal of money.
|Enviro Facts - Dolphins|
|WWF - Dolphin and Porpoise Facts|
|Whales on the Net - discovering whales|
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