Friday, June 05, 2009

Breathtakingly elegant and beautiful!

A woman has been killed by a Shark in the Red Sea.

According to this news flash, the Shark was an Oceanic Whitetip.
I was impressed by the official reaction. Much of what is being said makes perfect sense and the snorkeling and night diving ban is exactly what we have in place on Shark Reef, along with the rule that all tourists be supervised by experienced dive guides and that they descend and ascend along the reef. Not happy about the total chumming ban (cages being the logical alternative) but the Law is the Law and needs to be respected.
All-in-all, this is exactly how such an accident needs to be handled and big Kudos to the authorities for having done so.

I've gone rummaging for footage from those sites and have come up with the following two clips.
If only all Sharks were so easy to approach! And look at how gracefully they maneuver in total 3D: absolutely stunning!

I've never quite managed to dive with Oceanic Whitetips myself and chances for that are becoming slimmer by the day as this is one of the species most affected by the Shark fishing industry.

Can you guess why they have those conspicuous white tips on their fins?
I wasn't able to find the original paper (Myrberg, Arthur A., Jr. 1991. Distinctive Markings of Sharks: Ethological Considerations of Visual Function. J. Exper. Zool., Suppl. 5: 156-166) but this fascinating paper about possible explanations for the coloration of Whale Sharks carries this synopsis of Myrberg's assumption that they may be a case of aggressive Mimicry.

Myrberg’s (1991) examination of the functional relevance of the huge white tipped fins of the oceanic whitetip shark, Carcharhinus longimanus, clearly demonstrates this concept.
His ‘spot-lure’ theory describes how the silhouette of a nearby oceanic whitetip is easily seen; but from a distance the body’s silhouette becomes indistinct and only the moving white-tipped fins (‘spots’) remain visible. An observer would see a ‘pack’ or a ‘school’ of small, white objects moving closely together at a distance.
Oceanic whitetips are known to prey upon some of the fastest oceanic predatory fishes and it is unlikely they could chase down or sneak up on them in open water. Since many small prey fish are lightly coloured and move in schools, it is postulated that predatory fish would likely investigate by moving toward such ‘prey’. The scenario is that the whitetips spots lure faster moving prey to a distance where the shark’s rapid acceleration could overcome veering by the predatory fish.
Evidence is also provided that young oceanic whitetips hide their lures, as they may attract predators, by wearing a transitional ‘costume’ of black tipped fins.

Isn't that just amazing?
Anyway - Enjoy!

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