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  Seaweek 2004    

I live in the sea: Whales and Dolphins
The giants of the sea!

courtesy Great Barrier Reef Marine Park Authority

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.


Along the East and West coast of Australia you are most likely to see Humpback whales. In the southern waters Southern Right whales are sighted on their migration journey. Humpbacks have long fins while southern right have shorter, broader fins and rock like lumps around their chin and head.
Drawing courtesy Wet Paper
   


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

Interesting Fact
Whales and dolphins produce sounds (high-pitched whistles and groans) to communicate. Humpback whales are the most vocal of all and produce elaborate 'songs' that last for hours. Humpbacks in the same area sing the same songs and only the males sing. Singing seems to be most frequent at or near breeding grounds.
More than 30 species of whales and dolphins have been recorded in the Great Barrier Reef. The most commonly seen whales on the Reef are humpback and dwarf minke whales.

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.

   
Breeding
Female whales and dolphins give birth to one live young at a time after a ten to twelve month pregnancy. Most whales give birth in warmer waters during winter. For example, many humpback whales migrate from the Antarctic to give birth in waters along the Australian coastline. At birth, their offspring, called calves, can be over four metres long. The young calves gain weight rapidly during the first few months, however they remain close to their mothers and accompany them on the return journey of about 5000 kilometres to the Antarctic. After one year, the calves have grown to eight metres (more than half as long as their parents) and are independent.

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.

Threats to whales
Since the beginning of commercial harvesting many years ago, whales were hunted in the Great Barrier Reef for their blubber which was boiled into oil for lighting, lubrication, margarine, soap and cosmetics. Their baleen or 'whalebone' was softened and trimmed to make stiffeners for clothes, whips and umbrellas. However, as a result of whaling it was not long before whale populations began to dramatically decline, with a 95% reduction of the humback whale in Australian waters over a decade. Today, all whales are protected in Australian waters and since the cease of whaling in Australia in the early 1960s, their numbers have slowly started to increase. There are now believed to be around 5000 humpback whales and their population is increasing at about 10% per year.
Interesting Fact
The Blue Whale can be up to 30 metres long and is the largest creature ever to have lived.

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.


What you can do
· Do not kill, take, injure and/or interfere with whales and dolphins. Interference includes blocking their path, and harassing, chasing and herding them.
· Be alert and watch for whales and dolphins at all times when on the water.
· Avoid disturbance to mother whales and their calves especially from June to October.
· Slow down to minimise the risk of collision in areas where whales and dolphins have been sighted.
· Be quiet when you are around a whale or dolphin.
· If there is a sudden change in whale or dolphin behaviour, move away immediately.
· Report sick, injured, stranded or dead whales or dolphins to the Marine Animal Hotline, phone 1300 360 898 (24 hr).

When watching whales or dolphins:
· a vessel must not approach closer than 100m of a whale or 50m of a dolphin (or 300m of a whale in the Whale Protection Area in the Whitsunday Planning Area)
· if a vessel is closer than 300m of a whale or dolphin the vessel must be operated at a constant slow speed with negligible wake
· if there are two vessels within 300m of a whale or dolphin, all additional vessels must remain outside a 300m radius from the whale or dolphin
· you must not use a personal motorised watercraft (including jetskis) closer than 300m of a whale or dolphin
· you must not enter the water closer than 30m to a whale or dolphin
· you must not purposely touch or feed or attempt to touch or feed a whale or dolphin
· a fixed-wing aircraft must not approach below 1000 feet or within 300m of a whale or dolphin
· a helicopter must not approach below 1000 feet or within 1000m of a whale or dolphin
· in the Whitsunday Planning Area a helicopter must not approach below 2000 feet or within 1000m of a whale.

 
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Seaweek 2004 Home
1 Get started for
Seaweek 2004
2 Harmful Marine Debris
3 The EAC (East Australian Current)
4 Fish Fact File
5 Dugongs
6 Ghost Fishing -
Reducing the impact of fishing on non target species
7 First View - Giant Crab at home on the Slope
8 I live in the sea: Turtles the ancient mariners of the sea
9 I live in the sea: Sharks & Rays - they're more scared of us!
10 Sea stars
11 Marine algae
12 Sea jellies
13 Crustaceans
14 Echinoderms
15 Marine reptiles
16 Fisheries and Aquaculture
17 Whales & Dolphins
18 Protection of precious wetlands - success in New Zealand
19 Seaweek Discoveries in Vic Marine National Parks
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