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Charismatic Megafauna

Charismatic megafauna? This is just a pretentious way of saying large and awesome animals.

If you spend a lot of time underwater on the Great Barrier Reef you will eventually be confronted by a variety of large animals, many of them beautiful, some of them potentially dangerous, and the occasional one terrifying.

Dolphins and whales are often seen from the boat as we move between dive sites and are always welcomed with delight. Underwater, dolphins on the Barrier Reef are rare and elusive visitors, usually passing quickly by with only a cursory look. Whales have visited us underwater on a few exciting occasions, and we have often been bathed in the, incredibly powerful notes of the humpback whales eyrie and moving songs.

Click here for a larger picture. Manta rays, several metres from wingtip to wingtip, are sometimes seen, and are often curious. With slow motion flaps of their enormous wings they bank and dive gracefully around us, distracting us from our work for a while.

Click for a larger image Sea snakes are found on many southern reefs, their venom many times more powerful than the most deadly land snakes. Only the olive sea snake is common, a species that grows to about 1.2 metres long, but the rarer stokes sea snake may reach twice that length and can be quite intimidating. All sea snakes are attracted to movement and can swim faster than a diver but if you stay completely still they will lose interest and go about their business. It took us several years to become comfortable working around sea snakes but now they do not slow us down at all.

Click for a larger image And then there are sharks! Everyone asks about the sharks. On the Great Barrier Reef sharks are seen on most dives, usually harmless whitetip reef sharks up to about one and a half metres in length.

Click for a larger image Also common are the aggressive grey reef sharks, a solidly built whaler shark reaching two metres or so. These sharks can be very annoying, making fast, close approaches as they warn you not to interfere. Divers are sometimes bitten by these sharks; a single quick bite designed to frighten you away, but non-threatening behaviour usually calms them down before they reach that dangerous stage.

Larger, more dangerous sharks are fortunately rare and their normal daylight behaviour towards divers is usually quite relaxed. Silvertip whalers and black whalers may make one or two close passes before fading into the distance but their two to three metre size commands attention. Hammerheads and tiger sharks are at the top of the food chain, and always raise the pulse rate, not least because of their huge size.

Hammerheads may reach five or six metres and tigers four to five metres. These are the sharks that are equipped to handle large prey and easily capable of eating you if they choose. However, their normal behaviour is quite benign as long as they are not excited by the smell of dead or dying fish. We have left the water on a few occasions because of worries about aggressive shark behaviour but with familiarity it is usually possible to act non-threateningly and cautiously go about your work.

Click here for a larger image Closely related, but in a different category is the whale shark, the largest member of the shark family. This harmless species may grow to over 10 metres in length and is rarely seen. In 20 years of diving on the Barrier Reef we have only seen them underwater on two memorable occasions. With their blunt snouts, vast tail and white spotted pattern they make an unforgettable sight as they cruise effortlessly past.

The most horrific of the large animals that may be encountered on the reef are saltwater crocodiles. Yes, this largest member of the crocodile family is quite happy at sea, far from the rivers and estuaries where it is usually found. On the northern Great Barrier Reef crocodiles are often seen on reefs and islands tens of miles from the coast and we confronted one underwater on one unforgettable and terrifying occasion.

- Tony Ayling

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