Monday, July 19, 2010
How The Cape Fur Seal
Evades The Great White
Methodical Shark Ambush vs. Seal Speed and Skill …
Who Wins When and Why? Shark Expert Ryan Johnson Joins
Marine Scientists as They Deploy Innovative Real-World Experiments
to Rewrite Predator-Prey Science in National Geographic Channel Special
Escaping the Great White Premieres Friday, July 23, 2010, at 9 PM ET/PT
The great white shark is a tenacious predator that strikes with explosive power. But its favorite prey, the feisty Cape fur seal, manages to evade the jaws time and time again — a puzzle that has baffled scientists. Now, National Geographic Channel (NGC) heads to an epicenter of seal activity in South Africa’s Seal Island to investigate seals’ great escapes from the great white.
In Escaping the Great White, premiering Friday, July 23, 2010, at 9 PM ET/PT, shark scientist Ryan Johnson and colleague Alta de Vos plunge into a key battlefield between shark and seal to conduct a series of experiments that explore the many tactics in seals’ anti-shark defenses. Is the escape rate mostly a function of sheer swimming speed and instinctual reflexes? Why do seals exploit opportune hours when venturing into the sharks’ kill zone? And how does a strategic “buddy system” keep the seals out of the bellies of the mighty killer beast?
Head to South Africa’s Seal Island, where tens of thousands of seals gather on the shores, and sharks wait out farther at sea — invisible in deeper, darker water — preparing to ambush from below when seals venture out to feed. Johnson and de Vos’s first task is to find out why most shark victims are juveniles. Do sharks prefer the younger seals, or are they making more mistakes than the adults?
Using rubber decoys of one big seal and one small seal, the experiment is put into play and instigates awe-inspiring displays of power. Given the choice, Escaping the Great White shows sharks leaping out the water to target adult seals. The results clearly indicate that while sharks prefer adult seals, in real life, the adults have better mastered their survival strategies.
Escaping the Great White then tackles a puzzle that has baffled scientists for decades: the strategy of swimming in herds. One theory, called the Selfish Herd Hypothesis, is that individuals form a compact group to selfishly minimize their own chance of being eaten. But for nearly 30 years, the hypothesis has been scientifically elusive. Now, Johnson and de Vos devise an ingenious, yet simple experiment to test it.
They utilize expertly grouped seal decoys within shark-infested waters. The decoys fool the sharks into exploding out of the water to attack again and again. But the seals’ odds of getting hit are not equal, giving the scientists the first evidence to confirm the theory. Their observations confirm that the seal buddy system works … the closer a decoy is to its neighbor, the smaller its chances of drawing a deadly hit.
Finally, see how seals’ superior night vision leverages their escape strategies. Johnson and de Vos dive below to observe for themselves what the shark sees looking up from the depths at various times of day. They find that beginning just after sunrise, the shark has a clear silhouette view of his prey, while the seals are disadvantaged with a shadier image of their predator below. To steer clear of a shark hit, savvy adult seals avoid swimming during the time when they could easily be seen, and focus instead on late-night dives.
From beautiful, serene footage of seals playing underwater to magnificent, powerful displays of great whites breaching the water, Escaping the Great White opens a stunning window that illuminates new understanding in predator-prey science.
Escaping the Great White is produced by Africa Wildlife Films for National Geographic Channel. For Africa Wildlife Films, producer is Lynne Richardson, director is Phil Richardson, writer is Jonathon Cumming. For NGC, executive producer is Mike Welsh, senior vice president of production is Michael Cascio, executive vice president of content is Steve Burns.
For more information http://www.natgeotv.com/natureuntamed.
Posted by News 24/5 at 12:31 AM