How great white sharks hunt Cape fur seals, and how their quarry escapes comes down to one thing: physics.
The interaction between great whites and seals inhabiting False Bay in South Africa was studied by researchers Neil Hammerschlag at the University of Miami, and the late R. Aidan Martin at Canada’s University of British Columbia.
They detailed how the shark’s dark grey back, coupled with optical scattering through dimly lit water, helps the aquatic hunter elude detection by its prey. The prey is not without its defenses, however.
“Animal hunting in the ocean is rarely observed by humans,” said Hammerschlag in a press release. “The high frequency of attacks by white sharks on seals at our study site in South Africa provides a very unique opportunity to uncover new insights about predator-prey relationships.”
Shark predation on the seals peaks between May and August, when young Cape fur pups are most vulnerable.
As small groups of seals forage offshore, the great whites stalk them from below, well camouflaged against the darkness of the reef, while their targets are back lit by the sky above.
“Stealth and ambush are key elements in the white shark’s predatory strategy,” said Hammerschlag.
The sharks are most successful during the few hours around sunrise when the environment remains poorly lit. But as light begins penetrating into the depths of the bay, their hit rate drops off dramatically.
Moreover, a shark does not get an easy second chance after a failed initial attempt, as the small prey can agilely maneuver itself away from its hunter’s jaws.
The study was published online in the journal Marine Biology Research on Nov. 30.
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