Last year there were eight shark attacks recorded around near Perth in Western Australia, almost double the annual average over the last decade. Seven of those eight were attacks from the infamous great white shark.
Now a team of researchers from the University of Western Australia has come to the rescue. Professor Nathan Hart's research on shark vision has inspired the design of a wet suit that should be less visible to sharks or may even be shark-repelling. He spoke to Victoria Gill
Nathan - Well, there are actually two suits which have been designed based on the science we've done. The first is a black and white banded suit which is really designed to mimic a sea snake. So, it's warning coloration. There's anecdotal evidence that certain species of shark don't like eating sea snakes although we know that some do. There's also a camouflage design which works on the same principles as camouflage you see army people running around in, but in this case, specifically designed for the underwater light environment.
Victoria - The warning suit then is essentially you're disguising people as sea snakes.
Nathan - That's the idea, yeah. There's obviously some disruptive element to that pattern as well. What we did was to take our knowledge of the shark's spacial resolution, in other words their ability to resolve detail, to set the banding widths and that information was taken by the company who were designing the suits.
Victoria - So, what we're essentially looking at is quite a stripy suit.
Nathan - That's right. It's a stripy suit. We wanted to make sure that it would be visible to the shark from a certain distance away. Although sharks have very sensitive eyes for brightness, they're not actually acute in their vision. So, we're used to being able to discern very fine print in a book for example. Sharks have nowhere near that kind of ability and have very coarse vision, if you like. Because obviously, if you make the bands too small, the black and white eventually, just merge into grey at a certain distance. So, we needed to make sure it was very bold pattern and the sort of allied technology was really making sure that it resembled the sea snake. So, we needed to make sure that it was biologically proportionate.
Victoria - If we move on to the camouflage suit then, can you describe what that looks like first of all?
Nathan - If you think of a usual camouflage pattern, you might see someone in army gear. You normally have slightly different shades of green. In this case, it's slightly different shades of blue that are woven together in fairly large sort of swirls of colour. This specific pattern of the camouflage has come up with in concert with a wetsuit designer. So, it obviously has to be fashionable. But the different colours used are designed to match the light environment you see underwater.
Victoria - And what do you know about the shark's vision in order to understand how this camouflage would work for their visual system?
Nathan - So, although suits to us look blue. To a shark, they'll probably actually look like shades of grey because it turns out that sharks are probably colour blind. Now, we've looked at a range of shark species from things like bull sharks to carpet sharks and we're currently working on tigers and white sharks. But we expect they're going to be all very similar, basically that they have a single type of cone in their retina which makes them cone monochromats and then probably colour blind. So, the task then becomes matching brightness against the background rather than worrying about colour.
Victoria - So, these cones, these are pigment sensitive sensors in our eyes. So, we have three and if the shark only has one, then it would not be able to discern the different shades of colour that we can see. How did you discover that?
Nathan - So, we used a couple of different techniques. The first is a photometric technique where we actually take a piece of retina out the back of the shark's eye. We lay it flat and shine a very narrow beam of light through individual photoreceptor cells at the back of the eye, scan through the spectrum and find out what parts of the spectrum they're most sensitive to, and we think that's what colour they'd be most sensitive to. Doing that, we found that by surveying the retina, there was only one type present and we confirmed that using genetic techniques which is a way of screening what's expressed in the eye in terms of a protein or gene and we could confirm there was only one cone pigment there.
Victoria - Once you have made that discovery, did you immediately jumped to being able to take advantage of what you knew of the limitations in a shark's vision in order to camouflage people and prevent them from shark attacks? How did the work progress from there?
Nathan - That kind of connection was an application that's obviously always been there, but we're actually quite coincidentally approached by a company here who was interested in the space after the spate of shark attacks in WA. They sort of put their heads together and thought, "We must be able to design some sort of wetsuit that's harder for sharks to see or that scares sharks away." They found our group here UWA and so, it was very timely, based on the discoveries that we'd made.
Victoria - How do you test a shark proof wetsuit? It sounds like it could potentially be a very terrifying test.
Nathan - Well, we have lots of PhD students who are willing to swim with these suits on (just joking!). Really, it is very hard, in actual fact for all shark deterrents to test these things. Limited testing can be done in the lab, but ultimately, you have to take the product out into the wild, try and induce sharks to come up and investigate. Then you have to see how effective it is. We're at the very early stages of helping the company to test their wetsuit and it would be really nice to validate it and see if the science really works. There's likely to be no downside of the suit, but it would be really nice to know whether it decreases your chances.
Victoria - Does that really involve putting dummies in different wet suits underwater and inducing sharks to come and investigate and see what happens?
Nathan - Well obviously, there are ethical problems in putting either a person or even just an entire wetsuit, a mannequin in the water. So, we have to do it in a slightly more controlled way which is to use a piece of the wetsuit material, wrapped around something which doesn't resemble a human because obviously, we have to be very careful that we don't want to make any association between humans and food in an area where there are sharks.