By Ashley Mackin
By Ashley Mackin
Since surfing is one of the most popular activities in La Jolla, those who ride the waves at our beaches have heard the warnings about sharks.
And it’s not just surfers who may fear an encounter. Many kayakers and paddle-boarders have heard the theory that, to a shark, they look like seals or whales, a Great White’s favorite snack.
To assuage concerns, shark expert Ralph Collier set out to educate attendees at the “Sharks and You” lecture on Sept. 27, held in the former Neuroscience Institute Auditorium at 10640 John J. Hopkins Drive.
“From time to time, sharks and humans come together,” Collier told the crowd of approximately 100. “Sometimes it’s just by a bump on a surfboard, sometimes a shark will swim by and look you over — divers call it ‘being checked out’ — and some other times it’s not so lucky.”
He said sharks will investigate humans, surfboards, kayaks and boats using sight, smell and electronic currents. After that, if the shark cannot determine what it is, it takes a bite.
“Kayaks don’t look like grey whales ... [and] grey whales don’t scoot across the top of the water ... so when a shark bites a kayak, he’s biting because he doesn’t have the slightest idea what it is,” Collier said.
There are three different types of “attacks,” Collier explained. Predatory, when the shark is hunting; displacement, when they feel attacked and go on the defense; and investigative, when they are exploring.
Collier said in a separate interview with the
La Jolla Light
La Jolla Light
that many encounters with sharks involve no physical contact, and is the shark being inquisitive, not predatory.
Also addressed at the lecture was the childhood rumor that sharks can smell a drop of blood from miles away; apparently, they can sense more than that. Collier said sharks detect concentrations of one in 20- 30 million parts of water.
“Sharks have often been referred to as a ‘swimming nose’ ” he said. This is because water is constantly flowing through a sharks’ nose, providing fresh concentrations all the time. Collier used the analogy of walking into a house that smells like garlic. When you first walk in, it’s a strong smell, but after a few minutes, you’re used to it. Sharks don’t have that in the open ocean, so they move around in the water to see where scents are stronger and weaker. “That’s what sharks use when they hunt,” he said.
He explained that near the shark’s nose are Ampullae of Lorenzini, electro-receptors all sharks have. While some are more sensitive than others, most sharks have the ability to detect currents at five one-trillionths of a volt.
“That’s the equivalent of me standing in New York City and you standing in Los Angeles, taking a little flashlight, turning it on — and assuming there are no mountains — I would be able to see it,” Collier said.
Sharks use these sensors to detect muscle movement and heartbeats. “They are extremely sensitive,” Collier said. Hence why it’s suggested that you punch a shark in the nose if attacked.
Despite the notion of sharks being killing machines, Collier said sharks have cognitive ability, memory, and the ability to learn. He discussed past experiments in which sharks received training, which they remembered months later.
Collier’s research determined that Great White sharks are involved in many of the recorded attacks on humans. Seemingly common knowledge now, Collier’s research came 12 years before the movie “Jaws” was released.
See a video of a recent shark encounter off the La Jolla Coast here: