Up to about fifty million years ago both whales' and dolphins' ancestors lived on land. As mammals, whales and dolphins are warm blooded, have mammary glands to suckle their young and need to surface to breathe air. Since adapting to life in the water, whales' and dolphins' nostrils have moved to the top of their heads and are called 'blowholes'.

They have no hind limbs and their skin is extremely sensitive and smooth. Rather than having body hair to keep them warm, they have a thick insulating layer of fat or blubber under their skin. Their bodies are streamlined and their forelimbs are compact flippers used for balance and steering through the water.

Whales are divided into two groups: those with teeth and those without. Those with teeth are known as toothed whales, and include the sperm whale. Dolphins and porpoises are actually small-toothed whales. The other group of whales is known as baleen whales, and includes the blue whale and the humpback whale. These species are larger and they use baleen plates to sieve their prey from the sea.

As this humpback rolled onto its back you get a
chance to see the barnacles and cookie cutter
shark bites on it long wing like fin.
Photo courtesy Oceania Project

Toothed Whales
Whales with teeth are active hunters. Some, such as killer whales, eat sharks, seals, dolphins, birds, squid, fish and even other whales. Beaked whales and pilot whales all have teeth. The largest toothed whale is a sperm whale and can be up to 18 metres long.

Baleen Whales
Whales without teeth have baleen which consist of vertical plates fringed with stiff bristles hanging down from the upper jaw. Seawater is passed through the baleen and schools of tiny animals such as shrimp-like krill and microscopic plankton are filtered from the water.

Some baleen whales are called 'rorquals.' These whales have deeply grooved skin around their lower jaw and throat which forms a pouch that can expand allowing the whale to take in large mouthfuls of water. The tongue forces the water out again, filtering it through the baleen. Rorquals, found in the Great Barrier Reef include the humpback, minke and brydes whales. Those baleen whales that don't have throat grooves swim through the water with their mouths open, allowing the water and food to continuously flow through the baleen.

Feeding and breeding habits cause baleen whales to undergo some of the longest migrations of any animal. They spend the summers in the polar regions because food is plentiful with huge populations of krill, plankton and small fish. In winter, the whales move to warmer tropical waters like the Great Barrier Reef. Here they mate, or give birth.

Breathing in the sea
Whales and dolphins breathe air through their lungs and therefore must surface regularly. A small dolphin needs to surface for air about every two or three minutes. Baleen whales have blowholes divided into two, while toothed whales have a single blowhole. All whales and dolphins can stay submerged longer when feeding.

Senses
Whales and dolphins obtain much of the information about their surroundings from touch-sensitive organs in their skin and from sounds in the environment. Toothed whales, including all dolphins, use the added facility of echolocation to help them find food and navigate. This highly sophisticated sense involves producing a series of clicks that travels through the water, echoes off any object in its path and returns to the sender for interpretation. The sound is focused by fat deposits in the animal's forehead and lower jaw. This method of 'seeing' with sound is similar to ultrasound scanning.

Toothed whales seem to have the ability to sense the Earth's magnetic field. This assists them with navigation but can also lead them astray. It may be the reason for the mass strandings of whales that occur from time to time along the shoreline.

There is concern about apparent declines in populations of Indo-Pacific hump-backed dolphins and Irrawaddy dolphins throughout much of south-east Asia. Populations of these species around Australia may be the only ones that will survive into the next century.

Globally, despite restrictions on whaling, humans continue to have an impact on whale and dolphin numbers. Whales and dolphins are subject to a wide variety of impacts from human activities. Key human-related impacts include whale watching, boat strikes, and entanglements in nets. Other impacts that are thought to affect whales and dolphins are prey depletion, pollution, noise and habitat destruction from coastal development. Indirect impacts on whales and dolphins also include pesticides, heavy metals, pollution, oil spills and other contaminants accumulating in their bodies. These threats are difficult to control and the entire community should be aware of our individual responsibility to try to preserve these magnificent creatures.

A rare humpback on our doorstep
Recently, people visiting or living along the Australian east coast have had the rare and exciting opportunity to see a white humpback whale. It has been sighted over a number of years and has created a lot of interest. It was given the name Migaloo. In 2003 research was undertaken to see if it is a really an allbino.