The predatory behavior of sharks has has been a mystery for centuries. Now, researchers from the United States and Canada are using geographic profiling -- a criminal investigation tool used to track a connected series of crimes and locate where serial criminals live -- to examine the hunting patterns of white sharks in South Africa.
Great whites reach lengths of more than 6 meters (20 ft) and weighing up to 2,240 kilograms (4,938 lb), arguably the world's largest known predatory fish. It is the only surviving species of its ancient genus, Carcharodon (from the Greek words karcharos, which means sharp or jagged, and odous, tooth). The greatest concentrations of great whites are off the southern coasts of Australia, off South Africa, California, Mexico's Isla Guadalupe and to a degree in the Central Mediterranean, Adriatic Seas and New Zealand, where they are a protected species. One of the densest known population is found around Dyer Island, South Africa where this research was conducted
Using this geo profiling, scientists looked at the predatory interactions between white sharks and Cape fur seals at Seal Island in False Bay, South Africa. They found that sharks possess a well-defined anchor point or search base for hunting, but not where the chances of prey interception were greatest. Instead the attacks seemed to take place at strategic locations that could offer a balance of prey detection, capture rates, and inter-shark competition.
"Sharks are apex predators, so studies of shark hunting behavior are important for understanding their ecology and role in structuring marine communities," said Neil Hammerschlag, Ph.D. candidate at the University of Miami's Rosenstiel School of Marine and Atmospheric Science. "Our need for more knowledge of these fascinating animals has become critical because of recent drastic declines in their populations globally."
In an awesome display of power and acrobatic prowess, white sharks attack prey with a sudden vertical rush that propels them out of the water. "They hunt solitary juvenile Cape fur seals when light levels are low, stalking them from near the ocean floor to remain undetected, before launching a vertical attack," Hammerschlag said. "This strategy maximizes a shark's chances of catching a seal unaware thus initiating a fatal first strike. Stealth and ambush are key elements in the white shark's predatory strategy."
Hammerschlag and his collaborators from the University of British Columbia and Texas State University collected data on 340 natural predatory attacks by sharks on seals in False Bay. They were able to observe natural predation by great white sharks because attacks occur at the water's surface where they can be seen from a distance.
This could mean that white sharks refine their search patterns with experience, and learn to concentrate hunting efforts in locations with the highest probability of successful prey capture. It might also suggest that larger sharks competitively exclude smaller sharks from the prime hunting areas.
In addition to applications in law enforcement, geographic profiling has also been applied to studies of the foraging behavior of bats and bumblebees, the spread of infectious diseases in Africa, and the structure of terrorist cells in the Middle East. For more information about geographic profiling visit: www.txstate.edu/gii.
Edited and posted by Jason McManus.
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