Just how sharp are shark senses like sight, smell and hearing?

posted: 04/11/12
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Shark Senses
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The evolutionary triumph of sharks is displayed in many of their characteristics, but perhaps nowhere as definitively as in their tremendous ability to sense their environment. Seals, surfers and swimmers alike can run afoul of a shark's ability to see, smell, hear and detect signals humans can't even perceive. While not all sharks exhibit each of these senses to a T, here's what some of the top dogs can do.

Sharks have great hearing, and it's usually the sense they employ first when they're on the hunt because sound travels so well underwater. Sharks can start to pick up underwater noises farther away and at lower frequencies than people can, and those wavelengths are just the ones that are often most helpful in the ocean depths. For example, the sounds from swimming usually register in this range

Next comes scent. Sharks have a renowned talent for sniffing out the tiniest quantities of chemicals in the water surrounding them, but not over extremely vast distances — they tend to max out at around 450 yards (411 meters). They focus in on an odor by swinging their heads from side to side as they swim, so that their powerful nares can zone in on the source of the smell. Swimming into the current is another common shark strategy — it's often the direction a scent is arriving from.

It's only when they're about 50 feet (15 meters) away in clear water that most sharks really get a good look at what they're hunting, and muddy or murky waters can decrease that even farther. Recent evidence has also led researchers to suspect some shark species can also see colors to a certain degree, although much more than this is currently unknown. Despite these limitations, sharks do have some interesting ocular features well-suited to their environment. For example, they have reflective eyes like cats, so they get light through their retinas twice — but at levels about two times as efficiently as cats and about 10 times more than we could manage. So even though sharks don't have the sharpest vision in the animal kingdom, they're still better off in the depths than we are — and their other senses give them an advantage over much of their prey.

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