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Marine biologists and shark conservationists are concerned and confused by an upcoming Shark Week special. Entitled Zombie Sharks, it focuses on a physiological state called tonic immobility. Essentially, tonic immobility occurs when sharks that are flipped onto their backs go into a catatonic state, and it is used by researchers and aquarium veterinarians to safely study sharks. In Zombie Sharks, however, a SCUBA diver will attempt to become "the first person to induce underwater tonic immobility in a massive great white shark". Experts are asking a very important question about this plan to flip over a free-swimming great white shark: Why?
Dr. Edd Brooks, the manager of the shark research program at the Cape Eleuthera Institute, explains: "[Tonic immobility] is triggered by capture or restraint. It occurs after neither fight nor flight has worked and is designed to maximise the probability of surviving capture by a predator. To anthropomorphise it, it is the point where you know you cannot get away and fighting harder will only burn more energy and/or cause more injury, so you wait it out for another chance to escape."
Although Shark Week claims that tonic immobility is unique to sharks, Dr. Brooks points out that it has been seen in several other animals, including chickens and even humans who have been the victims of rape or other trauma. "In humans it has been described as the out-of-body 'it felt like it was happening to someone else' experience," he says.
“Experts are asking a very important question about the plan to flip over a free-swimming great white shark: Why?”
Researchers are sceptical about the educational or scientific value of flipping over a large shark underwater. The premise of the show is to duplicate the behaviour of orca whales flipping over great whites, but this has been known to scientists for at least 15 years. The description of Zombie Sharks correctly notes that scientists have been studying tonic immobility for years, and have studied it in many other species.
"I certainly don’t see the scientific value," says Dr. John Mandelman, the Director of Research at New England Aquarium. "Why do they need to confirm this other than to mess with a white shark for the sake of messing with a white shark?" Marine biologist Ivy Barremore, technical coordinator for the Mar Alliance, agrees. "It might be good TV, but it wouldn’t be good for anything else, including the shark," she notes.
Ocean conservationists are concerned that flipping over a free-swimming great white shark to see what happens is part of a growing trend of SCUBA divers harassing sharks, behaviour that Zombie Sharks host Eli Martinez has been criticized for participating in. "Tonic immobility is not something that should be used lightly on sharks," says Susana Navajas, the US coordinator for Shark Aid International. "[It] should only be performed on sharks when they're being studied scientifically or to help them. This kind of harassment of a protected species should not be allowed."
While research performed by Dr. Brooks and Dr. Mandleman has shown that tonic immobility is unlikely to have a lasting negative effect on the shark, there's simply no good reason for the events depicted in this show to occur.
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