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How Great White Sharks Hide in Plain Water

Excuse me for gushing, but great white sharks are bad ass. If the fact that they haven't changed much in millions of years doesn't mean that their true super-predators, I'm not sure what would. The thing is, great whites are hard to study, and not just...

Excuse me for gushing, but great white sharks are bad ass. If the fact that they haven’t changed much in millions of years doesn’t mean that they’re true super-predators, I’m not sure what would. The thing is, great whites are hard to study, and not just because of their prodigious toothiness. With their large ranges and small numbers, great whites are hard to find. That makes a new study on their feeding habits by the University of Miami just that much cooler.

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A group led by UM assistant professor Dr. Neil Hammerschlag studied the techniques employed by the great whites in their hunting of Cape fur seals in False Bay, South Africa. The study helps confirm a notion, long held by surfers whose silhouettes look somewhat like a seal’s, that great whites always stalk their prey from below. While that in itself isn’t surprising, Hammerschlag’s research, published in Marine Biology Research, showed that the sharks camouflage themselves by taking advantage of water’s light-scattering properties. In low light conditions, when sunlight is hitting the water at a sharp angle, light does not penetrate deep into the water, and what light does is heavily distorted, essentially hiding the shark in otherwise clear water.

Combine all that with great whites’ gray backs, which blend in against False Bay’s reef bottom, and the sharks are nearly impossible to see during the dim daylight hours. In fact, Hammerschlag’s team found that predatory activity was most intense within two hours of sunrise. As the day went on, and more direct sunlight was able to penetrate deeper into the water, the sharks slowed their hunt.

It’s not all hopeless for the seal, however. Hammerschlag found that most attacks were on groups of youngsters, potentially because older seals are more adept at detecting sharks. The seals also tend to be more maneuverable in the water than the great whites, and if a shark’s first bite doesn’t totally disable them, the seals are capable of escaping to safety. And as vicious as the sharks are, it’s not unheard of for a seal to injure one as it escapes.

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