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Tuesday, May 31, 2016

Do Sharks Mistake Wetsuited Humans With Seals?

Courtesy of WOWSA, Huntington Beach, California.

A recent shark attack in Southern California brought up a commonly held belief among swimmers, triathletes and ocean-goers.

This commonly reported belief is almost held sacrosanct among swimmers: "Wearing a wetsuit will make you look like a seal and therefore more likely to be attacked by a shark."

This oft-used quote is an indication how risky it is to avoid wearing a black wetsuit in areas where there are sharks.

But is it true?

According to researchers at the University of Western Australia and the University of Queensland, sharks are completely color blind and have only one type of photoreceptor in their retina.

This means they only see in monochrome and according to Professor Nathan Hart from the University of Western Australia, "It’s the high contrast against the water rather than the color itself which is probably attractive to sharks. So you should wear perhaps more muted colors or colors that match the background in the water better. It may now be possible to design swimming attire that has a lower visual contrast to sharks and is therefore less attractive to them."

That is, these researchers suggest that wearing a light blue wetsuit that matches the color of the sea will make surfers and swimmers less likely to become the victim of a shark attack.

While the U.S. Navy has conducted tests that suggested sharks were able to see yellow most clearly, Professor Hart said it was more the high contrast of yellow, not the color itself, that would increase the visibility for sharks.

During World War II, Japanese soldiers who were lost at sea due to naval conflicts were told to unwrap their fundoshi (traditional Japanese men's underwear) and let the fabric float behind them in order to make their appearance (silhouette) larger in order to ward off sharks. So instead of color, the Japanese believe that size is a greater impediment to attacks than color.

This line of thought is consistent with shark divers who work on the film crews for the episodes of Shark Week broadcast on the Discovery Channel.

But Fred Buyle, a Belgian freediver who is considered to be one of the world's foremost shark taggers, has a unique perspective and experience with sharks. Because sharks co-exist peacefully with freedivers, Buyle can attach transmitters to their dorsal fins so they can be tracked by scientists.

Buyle and his fellow freedivers wear wetsuits to deter accidental attacks. Sharks reportedly bump their noses into potential prey and emit electrical signals. If the signals conduct, the chances of an attack increase. Wetsuits do not interact with these electrical signals like human skin does. As Buyle says, "I am happy to dive with them; sharks don't like to eat humans."

But he also has an oft-stated reminder, "We will never change the shark's behavior. The most important thing is to respect that the ocean is a wild environment. This is the shark's home. You are just a visitor to it."

Whether as a neoprene-clad triathlete, an open water swimmer or a freediver, Buyle reminds us that sharks are disturbed by things other than wetsuits:

While many (most?) people believe that sharks mistake a human with a black wetsuit for a seal (i.e., meal), we have never agreed with that assumption. It just does not make any evolutionary sense to us. We think sharks are much too intelligent and selective to make that assumed mistake, primarily because sharks have been around the oceans for 400 million years.

Sharks thrived in the world's oceans for 200 million years earlier than the dinosaurs and nearly 400 million years before the first hominids - they are evolutionary marvels. Sharks have what it takes to exist in a world where many species have come and gone. But as the apex predator in the oceans, the sharks have not only survived, but clearly thrived with their remarkable biological characteristics and well-developed hunting and eating abilities. For 400 million years, sharks have known what is what in the ocean by their well-honed senses.

But then throw in humans and, over the last few decades, wetsuits have been introduced into the world's oceans. Shark's senses must be well-used as they studied the new phenomena of mankind in the ocean. This new commercial development of neoprene in the ocean is something that the world's shark radar must recognize. But to think that sharks are confused between seals and a human with a black wetsuit is to not give the senses of sharks enough credit. Sharks did not evolve and exist for 400 million years by making mistakes in its hunting strategies and choices.

E.O. Wilson, the famous sociobiologist, said about humans, "We are not afraid of predators, we’re transfixed by them, prone to weave stories and fables and chatter endlessly about them, because fascination creates preparedness, and preparedness, survival. In a deeply tribal way, we love our monsters."

Contemporary society has certainly made a modern-day monster out of sharks.

Are sharks' complex hunting behavior truly reduced to making mistakes between sea lions and humans wearing neoprene? After all these milleania, a shark's confusion between a seal and a triathlete in a wetsuit or a surfer with neoprene is not a natural conclusion to us. Sharks' abilities are much more profound and developed.

Sharks, according to scientists who track and study them, spend not only a great deal of time migrating from point to point, but also spending time simply swimming around and hanging out swimming in circles (see video below by Save Our Seas of the whereabouts of a Great White Shark in False Bay over a 24-hour period).

We would think that sharks might be curious as to what a human might be or might taste like to a shark, but we do not imagine that sharks mistake a human for a seal, or vice versa, whether or not the human is attired in black neoprene. Sharks have a profound understanding of what seals do, how they smell, how they swim, how they swim, their heart rate, difference between juvenile and adult seals, and where they live. Here is a video captured of the interaction between a shark and seal. We can imagine any human moving similarly to that frightened seal.

People believe sharks are attracted by splashing and vibrations in the water that can lead to shark encounters. But what animal or fish in the oceans resemble the highly inefficient movement of humans in the water? The way seals or other shark prey move in the water is a far cry from even the most efficient freestyler among homo sapiens.

Sharks are sometimes described as wild animals. But 'wild' has an implication of being unsophisticated. But that is not the case with sharks. Sharks can identify any prey and can do it as well as any other creature in the ocean. Like sea lions and other prey in the oceans, sharks can easily sense humans in wetsuits via their sense of smell, sight, movement, and its bioelectrical facilities. For the shark, a denizen of the ocean that has evolved over 400 million years, a human is a new creature. Sharks do not often run into humans, at least relative to all the other creatures it encounters in the course of its natural life in the oceans.

So while sharks may be curious, and may take an exploratory bite every now and then among its innumerable encounters with humans, we find it illogical and implausible to think a shark cannot distinguish between a human and its other prey - black neoprene or not.

But perhaps this film and marine biologists have the answer to these questions:

(1) Do sharks indeed mistake humans in wetsuits for seals?
(2) If there is human blood in the water, does a shark mistake this blood for the blood of its natural prey?

Similar to human smelling senses that are developed to trigger hunger when a delicious meal is cooking, we wonder if human blood truly triggers hunger and a need to initiate a feeding frenzy among sharks.

Our belief is that the answers to these questions is no.

Copyright © 2016 by World Open Water Swimming Association

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