Sharks, The Perfect Predator
Shark facts by Alessandro De Maddalena
What have coal, shoes, car licence plates, paint-cans, a hat, a roll of tar paper, two tins of green peas, an unopened can of salmon, a 900g coil of copper wire, small barrels, nuts and bolts, driftwood, a tom-tom, a wallet, boat cushions, the head and forequarters of a crocodile, hyenas, monkeys, chickens, pigs, cattle, donkeys, the hind leg of a sheep, a dog and rats got in common?
The answer is that these items have all been found in the stomachs of dead tiger sharks.
How does any shark get the fresh water it needs? Bony fish drink sea water, but sharks do not. The salt content of shark tissue is higher because it retains metabolic waste. Water naturally diffuses through external cell membranes in an osmotic process, and a rectal gland removes excess salt from the blood.
The nurse shark literally sucks its prey out of its hiding place, into its mouth, often accompanied by a loud popping noise.
Sting rays are the preferred prey of the great hammerhead. All this is the sort of useful information I gleaned from this book.
It's not an easy read, nor is it a coffee-table book liberally illustrated with fine colour plates. It's written more in the manner of a degree-course textbook, but ingest some of the thousands of facts and figures in its pages and you will be well ready to flaunt useful snippets.
On the dive deck this may set you apart as a perceived expert - and if you manage to retain, say, 50% of it, you may well be one!
John Bantin
Jacana Media
ISBN 9781770095595
Softback, 198pp, 15 euros
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