Reality TV: Camera-toting sharks hunt seals in kelp forests

phys.org | 2/13/2019 | Staff
Cocoa_Candy12 (Posted by) Level 3
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Great white sharks fitted with cameras on their dorsal fins have been filmed for the first time stalking prey in dense kelp forests long thought to be no-go zones for the top-level predators.

The thrilling, shark's-eye views show the massive carnivores manoeuvering effortlessly thought thick kelp fronds suspended in the water like giant bean stalks.

Shark—off - Coast - South - Africa—spots - Cape

Suddenly one shark—off the coast of South Africa—spots several Cape fur seals, and the chase is on.

"The shark drastically increased its activity when it saw the seals, and all sharks raised activity in the presence of kelp," Oliver Jewell, a graduate student at Murdoch University in Western Australia and lead author of a study in Biology Letters, told AFP.

Great - Whites—which - Metres - Feet - Kilos

Great whites—which can grow up to six metres (20 feet) long and weigh more than 2,500 kilos (5,500 pounds)—gather along the coast of South Africa in winter to feed on seals that congregate on rock formations at the water's edge.

To execute an "open-water ambush," previous research has shown, the sharks close in on colonies at dawn or dusk, swimming in deep waters below their unsuspecting prey.

Seals - Dim - Light - Sharks - Silhouette

Invisible to the seals in the dim light, the sharks scan from below for a silhouette.

Zeroing in on a victim, a great white "charges up to grab the seal at the surface and breaches clear of the water," Jewell said.

Dyer - Island - Jewell - Colleagues - Field

Near Dyer island, where Jewell and his colleagues conducted their field research in 2014, this kind of attack appears to occur less frequently.

One reason, they speculated, may be the region's thick kelp forests, long thought to be a natural barrier to sharks and a refuge for seals avoiding their razor-sharp teeth.

Jewell - Team - Whites - High-resolution - Motion

To find out if that was true, Jewell and his team fitted eight great whites with high-resolution motion sensor tags—the equivalent of underwater Fitbits—with in-built cameras.

"We attract the sharks using a line baited with a...
(Excerpt) Read more at: phys.org
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