Environment

Shark Week is here — and this University of Miami expert plays a big part

Shark Week: Psychology and physiology

How a shark's predatory senses work.
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How a shark's predatory senses work.

Neil Hammerschlag wants to share his love of sharks. They are not the man-eating beasts stereotyped in pop culture lore. They do not rampage through oceans to the foreboding beat of “Jaws” theme music.

“They are incredibly amazing creatures,” said Hammerschlag, a renowned shark scientist and associate professor at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science and the Abess Center for Ecosystem Science and Policy.

The Discovery Channel and ravenous shark fans agree with Hammerschlag. The 31st edition of “Shark Week” airs July 28-Aug. 4. Hammerschlag stars in two of the 18 shows featuring spectacular footage of sharks in their native habitat.

In “Andrew Mayne: Ghost Diver,” which will be shown Aug. 2 at 9 p.m., Hammerschlag trains celebrity illusionist Mayne how to dive with great white sharks. Mayne’s goal is to make himself invisible to the sharks swimming around him.

“The idea is for Andrew to come out of the shark cage and be undetected, crazy as that sounds,” Hammerschlag said. “He uses a high-tech covering over his wetsuit to confuse or deceive the sharks into not noticing that he is among them. You have to watch the show to see if it works.”

The personality of great whites made Mayne’s trick extra tricky.

“They are very curious animals and if you’re in an area where they are feeding, I wouldn’t recommend getting out of the cage,” Hammerschlag said. “They can sneak up on you out of nowhere. They are super silent and built to be an ambush predator.”

The teeth of great whites are as sharp as scalpels. The top teeth are serrated like steak knives. The thicker bottom teeth act as a fork. When a tooth breaks, another grows in to replace it.

“They have an unlimited supply of teeth and they use their teeth to investigate objects,” Hammerschlag said. “So it can be an unpleasant experience for the person being investigated. It’s like if I pick up an ant as gently as possible, it’s probably still not a good end for the ant.”

To Hammerschlag, the show was an opportunity to teach Mayne and a large audience about the sensory system of sharks that puts them at the top of the food chain.

“Their nasal cavities are adapted so that they can smell chemicals in the water at low concentrations, particularly those emitted by fish, from a mile or two away,” he said. “They are like underwater bloodhounds.”

Sharks can’t see colors or make out sharp edges but the high number of rods in their eyes make them extremely light-sensitive with good vision in a dark, murky blue-green environment.

As for touch, sharks can sense movement, vibration and electrical fields.

“Salt water is a conductive medium and they have evolved to take advantage,” Hammerschlag said. “A breathing fish creates a weak electrical field by pumping water over its gills and a shark can detect that from three miles away.”

Sharks hear through the inner ear, the lateral line (which runs along both sides of the shark’s body and is filled with cells that sense vibration and movement) and body pores.

“The ocean is a loud and noisy place,” Hammerschlag said. “They are sensitive to low-frequency sounds and repeated sounds, like the ringing of a dinner bell.”

Hammerschlag’s first show, “Air Jaws Strikes Back” (Tuesday, July 30, 10 p.m.) takes him back to his native South Africa to study a great-white hot spot where sharks hunt seals in shallow water and seals mount their own brave counterattack.

These seals mobbed a shark and chased him off.

Great whites have been disappearing from South Africa’s waters since 2015 for reasons that remain unexplained. At Hammerschlag’s former research site, Seal Island, no great whites — famous for leaping out of the water during their attacks — have been spotted for more than a year, and seven-gill sharks have moved in from offshore kelp beds. So he and naturalist Chris Fallows explored a new hot spot beneath a cliff on the Robberg Peninsula in Plettenberg Bay.

“What’s exciting is it’s close to shore and you can stand on the cliff and watch predator-prey interaction in shallow water,” Hammerschlag said. “Everything we’d previously learned about great white hunting strategies occurred in dark water at sunrise and sunset when they’d launch a vertical attack from very deep targeting single seals.”

With a bird’s-eye view, Hammerschlag observed how feeding attacks unfolded with 10-foot, 1,500-pound sharks charging into groups of Cape fur seals in five feet of clear water.

“We learned about the seals’ defense tactics and documented like never before how they try to fend off the sharks,” he said. “They are not as helpless as they seem. They will bite back. But the constant stress on prey can affect their nutrition, reproduction and population.”

Hammerschlag and Fallows also witnessed illegal fishing for great whites, which is a protected species in South Africa. They are collaborating with LiveSpotr, a smartphone app that allows the public to report great white sightings or harassment.

“We need citizen scientists to upload what they see,” he said. “We hope it will act as a deterrent and a way to gather data.”

Hammerschlag, director of UM’s Shark Research and Conservation Program, embraces “Shark Week” because it creates an educational platform for scientists. He reinforces the message that sharks are in trouble. Of the 511 known species, 20 percent face the threat of extinction, including hammerheads. About 100 million sharks per year are being killed and removed from oceans.

“The biggest threat is overfishing for meat and fins,” said Hammerschlag, who runs a shark-tagging lab at UM and recently co-authored a study in Nature magazine. “Habitat destruction and pollution are causing certain populations to decline. It is difficult for sharks to recover in light of these worsening synergistic effects.

“’Shark Week’ is such a popular summertime event that it’s a great way to spread the word on shark conservation.”

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