Dolphins and Whales

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.

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.

Seals and Sealions

Seals and sea lions are mammals that live in the oceans all around the world. The ancestors of seals and sea lions were land mammals that returned to the oceans millions of years ago. It is thought that these ancestors were related to early dogs, cats and other carnivores. Being mammals, they breathe air, are warm-blooded and give birth to live young which they suckle with milk produced by the mother. They are all amphibious, able to live on land or in the water. They are more at home in the water, however, and often only come ashore to give birth to their young and shed their fur and grow a new layer (moult). All the pinnipeds have 4 flippers - 2 at the front (foreflippers) and 2 at the back (hind flippers). These flippers are the same as the four legs of most other mammals, but have become specialised for swimming. There are two main groups - the otarid seals which includes the fur seals and sea lions, and the phocid seals, sometimes known as true seals. The most obvious difference between the two groups is that the fur seals and sea lions can turn their hind flippers forwards and walk on land, whereas the phocid seals have to wriggle along on land like giant slugs.

What do they look like?
Pinnipeds come in a great variety of sizes, but all have a similar basic appearance. They all have streamlined bodies for fast and agile swimming. They all have fur, short on some, very thick on others, and long whiskers on their muzzles. In most species the male is bigger than the female. All pinnipeds have 4 flippers - 2 at the front (foreflippers) and 2 at the back (hindflippers). Some can turn their hind flippers forwards and walk on land, whereas others have to wriggle along on land like giant slugs, dragging their hindflippers behind them. The males of elephant seals have noses with enormous sacs which flap when they move. Most seals are a brown or grey colour but lighter on the belly. Some have spotted coats. Young seals (pups) often have very different fur to their parents. They have to stay on land until this fur is replaced by proper fur that will keep them warm in the water. Many seals and sea lions form large breeding colonies on beaches but can also be found in smaller numbers on land. At sea they are usually solitary.

Where do they live?
Seals and seal lions are found in most seas of the world. Some are found only in inland seas. Others live on and under the ice of the polar oceans. Still others live in the sub-tropics. Each species, however, tends to have their own preferred climate. All species must come ashore at least once a year for the females to give birth and for all to moult their fur. They may ‘haul-out’ on beaches, rocky headlands or even onto floating ice floes. As they are more visible when they are ashore, more is known about this part of their lives than their activities at sea. There they are usually solitary and may wander enormous distances in both deep and shallow waters, but generally return to their original haul-out site, coming ashore to breed and moult. During the breeding season, they can become very territorial, mainly on the land but also sometimes underwater. In some species the males have territories they try to fill with many females, defending it aggressively against any other males that attempt to “steal” their females.

How and what do they eat?
All seals and sea lions are carnivores. They need speed and agility in the water to catch their main food, fish. Squid is the main diet of some species. Most species have large canine teeth for gripping their prey. They have developed a special ability to dive to great depths for up to two hours and have enormous eyes for seeing in the gloomy depths. Others eat shrimp-like zooplankton (krill) which they strain through specially shaped teeth. Still others eat penguins and even other seals! They have large cutting teeth for demolishing prey that is too large to swallow all at once. Some forage among rocky reefs in shallow coastal waters looking for fish. They are important top predators, in some ecosystems, being the only significant predator of some animals. When seals and sea lions are on land to breed and moult, they can go without food for many weeks at a time.

What eats them?
Seals and sea lions are close to the top of the food chain. In the water they are hunted by sharks but are usually too agile and fast to be caught. However, some of the larger seals that are not so agile or are diseased may be hunted by white pointer sharks. Killer whales are probably the main predator of most temperate and polar species and have been observed throwing themselves onto beaches to take seals, then sliding back into the water. Some seals are also eaten by other, larger species of seals. On land the main predators are humans and many seals and fur seals are killed each year by commercial sealing operations for their fur and meat. Some species have disappeared as a result of sealing and several species are currently endangered.

How do they grow and reproduce?
Seals and sea lions usually form large groups on land or on ice floes during the breeding season (once a year for most species). Mating and giving birth (whelping) occur at these times. Some species may mate in the water, but all have to return to land (or ice) for whelping. Most pinnipeds have a gestation period of about one year. Some species can stop the development of the young pup during pregnancy for a few months, resuming development later on so that pups are born about one year after mating. Very few mammals can do this. Only one pup is born at a time. The pups are sometimes born with a thick fur coat that is warm in air but not in water, and so have to stay on land or ice until their first moult. After this they grow an adult coat that will keep them warm in water. All seal and sea lion pups spend at least their first week or two on land where they grow at a great rate on their mother’s very rich and fatty milk. Most seals and sea lions mate again soon after giving birth or weaning their young.

Who do they live with?
Seals that beach themselves on land often gather in huge colonies consisting of many thousands of animals. Those that gather on ice, however, tend to be found in smaller, less sociable groups. Little is known about the activity of many seals when at sea, but they are usually seen alone or in small groups. Seals and sea lions also have their own species of parasites, both internally (like intestinal worms) and externally (like lice). In some parts of the world, seals and sea lions live very close to humans, and may follow fishing boats looking for scraps thrown overboard.

Their connection with people.
People have hunted seals and sea lions since ancient times. For many coastal native tribes in the colder parts of the world, seals and sea lions have been important sources of food and skins. Many species were over-hunted last century and at the beginning of this century, and some were wiped out. Others are still endangered today. Commercial hunting of seals continues in many places in the world. Many seals are shot by fishermen who believe the seals are stealing their fish. Others are drowned when they get caught in fishing nets. Some good news, though, is that the numbers of many species of seal and sea lion that were once hunted are now increasing. In many places, seals have become a tourist attraction and people visit them just to see them in the wild and photograph them. Scientists study seals around the world, counting them, seeing what they eat and how deep they can dive. Seals and sea lions are also kept in captivity in many countries where their agility and playful natures are admired by visitors, especially when they perform tricks like balancing balls on their muzzles.