Biodiversity #5 – The shark has the greatest electrical sensitivity of any animal, and use the ampullae of Lorenzini to detect the electromagnetic fields that all living things produce. Sharks have keen olfactory senses with some species able to detect one part per million of blood in seawater; they can also determine the direction of a given scent. Though they have good night vision they are effectively colourblind. Many sharks need to keep moving to breathe, but it has been found that the spinal cord, rather than its brain, coordinates swimming, so many sharks can swim while sleeping.
Most sharks live 20 to 30 years, but a few species live for over 100 years. Only four species have been known to attack humans, and all four have been filmed (without a cage) in the wild. It is reliably estimated that 100 million sharks are slaughtered annually by humans, with an exploitation rate of up to 7.9%. With an average rebound rate of 4.9% many species may be driven to extinction with a few decades. There are places in Australia where you can dive in the presence of sharks both in the ocean and out of it. Plan to while you still can.
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