When great white sharks attack - and how seals try to get away

By Colin Ricketts - 10 Dec 2011 20:45:0 GMT
When great white sharks attack - and how seals try to get away

Great white shark via Shutterstock

Scientists have shed new light on what they call 'predator-prey interactions in the marine environment', or to put it more simply, why great white sharks are such bad news for Cape fur seals.

The research team of Dr. Neil Hammerschlag from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a University of British Columbia scientist looked at the ways in which great white sharks go about getting their teeth into Cape fur seals in South Africa's False Bay.

"Animal hunting in the ocean is rarely observed by humans," said Hammerschalg, director of the RJ Dunlap Marine Conservation Program at UM. "The high frequency of attacks by great white sharks on seals at our study site in South Africa provides a very unique opportunity to uncover new insights about predator-prey relationships."

The paper examines how the sharks, which are ambush predators, try and get as close as possible to their prey without blowing their cover. And, how the seals try and get away from their deadly predators.

Important factors in this relationship are both animals' senses (primarily sight), their speed and the prey's response to attack.

Hammerschlag found that sharks are cunning. Knowing that one of the seals primary defences is to gather in groups to benefit from extra pairs of eyes, they target their attacks against youngsters in smaller groups and particularly pick out those who have recently fed and are suffering a post feeding slump in energy.

Great White Shark

Great White Shark Attack via Shutterstock

Examining the way water and light react together was also vital to the study's explanation of why sharks attack first thing in the morning. The shark's dark back is better camouflage in low light conditions - and light is scattered by the water in the mornings - and the success rate of their attacks rises to 55% as against 40% in better lighted times of the day.

Great white sharks also rely on getting their prey first time, with their attack burst reaching around 11 metres per second and often propelling them high out of the water. Once they have lost that initial battle, the seal starts to even up the score with its shorter turning distance and greater manoeuvrability - the hunted can even become the hunters and seriously injure their would-be killers.

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Topics: Sharks / Mammals