03 April, 2014

Why these wetsuits will never protect you from sharks


Shark repellents seem to creep up in the news once every three months or so.  Some make me laugh, some show promise, and others straight up vex me.  The above wetsuits fall into the latter because they can never work, definitely not for the reasons the sellers are trying to convince you, at least.  So let’s examine the pseuodoscience behind this, delve into the true science, and see how these suits measure up. 

The concept behind the wetsuit is that the coloration on them mimics the colouration of sea snakes, and that sharks will avoid sea snakes (or anything black and white striped) because they are poisonous. Therefore any shark would recognize the coloration of the sea snake on your wetsuit as poisonous and avoid you – thus preventing shark attacks. 

This idea is based on Batesian mimicry, which is when non-harmful species mimic the 'warning'coloration of a harmful species in order to reduce their predation risk from a common predator.  The classic example of this is the monarch butterfly and the viceroy:


The monarch (on the right) is poisonous.  If a predator – like a Blue Jay – consumes the monarch, it will be instantly sick.  This instantaneous negative reaction is key, because the Blue Jay immediately associates being ill with the consumption of that orange and black coloured prey.  If the negative reaction is delayed, say a few minutes later after the Blue Jay has eaten another beetle, the Blue Jay will not learn that it was the monarch that caused the reaction.  So, the monarch has taught the Blue Jay to avoid orange and black coloured butterflies.


The non-harmful viceroy, through the random luck of mutations and natural selection, mimics the coloration of the monarch butterfly.  This is because these warning colours are highly advantageous, thus increasing the viceroy’s fitness.    

The same applies to the Eastern coral snake and the scarlet king snake, several species of dart frogs, and my personal favourite – the Hawkmoth larva and green parrot snake.    

Do you see the failings of taking this concept and applying it to snakes and wetsuits?

For one, aversion of particular colourations is a learned behaviour.  Predators, like the Blue Jay, are not born knowing to avoid orange and black.  They have to experience it first. 
a.       This means that a shark must have already eaten a sea snake and then something negative happened to it immediately.  This wetsuit would only work on that individual shark, not all sharks.
b.      Tiger sharks eat sea snakes – some poisonous - as part of their diets.  So you’re dressing up as a tiger shark prey item, smart.
c.       As for the sharks that don’t eat poisonous sea snakes, they would have not learned aversion to the colouration now would they?    

Secondly, the effectiveness of warning colouration is measured on the species level (less monarchs are eaten overall – the species survives) not the individual level.  So even if sharks did avoid anything with black and white stripes, that doesn't necessarily mean you would be 100% safe.  This is because learned behaviours often have to be relearned.  The Blue Jay in the above example won’t eat another monarch for quite some time, but next season he may very well have forgotten and experience another negative reaction to orange and black butterflies to remind him that they should be avoided (unless he eats a viceroy first and has no negative reaction... see how this goes?).   

So, applying what we now know from above, what are the odds that a non-Tiger shark will approach you in the water combined with 2) the individual shark approaching you has recently eaten a poisonous snake of black and white colouration and 3) it was ill immediately after eating that snake, therefore has learned an aversion??  ZERO. 

The second hypothesis, and style of wetsuit, concerns cryptic colouration.  They say,

“So while a shark may locate its prey through a number of different means, it is less likely to attack if the target cannot be seen.

Yes, because sharks only attempt to eat what they can see.  This is why sharks only eat prey in clear water and high light levels... wait, what?  Bottom line is, if you are in the water near a shark, it has already noticed you.  Several variables afterwards will determine whether or not it comes in for a closer inspection, and none of those variables concern what color your wetsuit is.  

And remember, you are still more likely to be killed by a hot dog.  

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