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Marine Mammals Including Whales & Dolphins

Superficially at least, whales and dolphins look like fish, however the fact that they are mammals becomes obvious on closer inspection since they are warm-blooded, breathe air with lungs, suckle their young with milk, and have elaborated brains.

Whales are divided up into two main groups; those with teeth and those without.

Whales without teeth feed by filtering water containing food through curtains of "baleen" - up to 300 individual flattened plates, which hang from the roof of the whales mouth in the fashion of vertical blinds. The inner surface of the plates is fringed with bristles, frayed at the edges like a worn paintbrush, which trap prey such as krill (shrimp-like crustaceans up to 5cm long), plankton or small fish. These whales are also characterised by double blowholes.

The other group, the Odontocetes, have teeth and actively chase prey such as fish and squid. This group includes the Beaked Whales, Killer Whales, Pilot Whales, Dolphins and Porpoises and is characterised by a single blowhole.

Generally the larger Whales are members of the Baleen group, producing their massive bulk from the smallest prey. Of the toothed whales the sperm whale is the only giant, measuring up to 18 meters in length. Interestingly, the developing foetus of a baleen whale has tooth buds at early stages.

Whale (And Dolphin) Watching

Each year, as the waters of the Antarctic begin to freeze over, whales move north. Fat with blubber from their summer feast of krill, some females pregnant from the previous season's frolics, they move into warmer waters of the Great Barrier Reef to engage in courtship, mating, birthing and calf-rearing activities. In Australia, the past ten years have seen a growing fascination with the observation of marine mammals in their natural environment. The timing of this trend has come several decades after the last commercial exploitation of these species in this country. In the past whalers studied the movements of humpbacks and lay in ambush. Now it is the whale watchers who anticipate their arrival.

Keeping close to the coast, the majority head up the East Coast of Australia from June and enter the sheltered waters of the Great Barrier Reef. Sightings are regular from then through until late October and include: Humpback Whale

  • Irrawaddy Dolphin
  • Indopacific Humpback Dolphin
  • Bottlenose Dolphin
  • Minke Whale
  • Humpback Whale
  • Bride's Whale
  • Shortfinned Pilot Whale
  • Spinner Dolphin

Further offshore, sightings can include:

  • Sperm Whale
  • Fraser's Dolphin
  • Melonheaded Whale
  • False Killer Whale
  • Striped Dolphin
  • Pygmy Killer Whale
  • Killer Whale (Orca)
  • Pygmy Sperm Whale
  • Dwarf Sperm Whale

Many of the various operators will stop or slow up and observe whales during the season. There are restrictions on how close you may go so vessels keep a certain distance. However during the whale season many whales have approached divers, coming quite close to them and seemingly studying them. This is a rare and wonderful experience with those privileged few feeling touched by the experience and lost for words.

Environmental Concerns

Despite restrictions on the whaling, we humans still mange to kill great numbers. Some Dolphin species associate closely with tuna and as a result are caught in nets. Half a million dolphins were killed by Tuna fisherman in 1974. Restrictions on net lengths in Australian Waters have cut down on mortalities while adaptations to nets including who assist the dolphins to escape, will hopefully, make tuna genuinely "Dolphin friendly"

Discarded materials, particularly plastics continue to kill many animals, which become entangled in them or swallow them. An estimated 100 000 tonnes of plastic fishing gear is discarded or lost each year worldwide while an estimated 450 000 plastic containers are dumped at sea everyday.

Another major threat to Whales is chemical pollution. Toxins enter the ocean as sewerage discharge, run-off, and waste from industrial facilities, from atmosphere and from ships. The result is interference with reproduction and the immune system as well as direct mortalities.

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Diving Cairns - The ultimate guide to a diving holiday on North Queensland's Great Barrier Reef