Taking a bite out of science: Experiments with Great White Sharks

A lot of the research that we do in psychology involves experiments with people. Usually we’ll put a bunch of people through a task that we’ve designed. Some of them may find it easy and some difficult, but usually we’re interested in understanding the way that they perform the task rather than simply how well they do. Hopefully, under all the messy data that they give us is a meaningful pattern in what they are doing.

I study visual perception, so experiments in my lab usually have undergraduates at the University of Auckland come along to a quiet room where they sit at a computer and press keys on the keyboard when they see certain things (faces, objects) on the screen. We can explain to the participants the task they have before them, and apart from occasionally getting a little bored our participants seem satisfied enough by the session. In general, my students and I don’t need to worry about our personal safety.

But what if you want to perform experiments with great white sharks? It’s scary enough just imagining being anywhere near these giant carnivores; and of course they are etched in our subconscious as a manifestation of terror:

My colleague Dr Alex Taylor is interested in understanding intelligence, and particularly how it has evolved. To do this, most of his work focuses on problem-solving in non-human animals. He and his colleagues at Auckland, particularly Prof Russell Gray, have worked extensively with New Caledonian crows and demonstrated how, like humans, chimpanzees, and orang-utans, they use tools that they craft in order to get food. A video from BBC last year featured Alex’s work with these crows and just how clever they are:

Recently, he has worked as part of a team of researchers to study complex behaviour in great white sharks. Much is known about these sharks’ athletic gifts, and their ability to smell tiny specks of blood in the water. But sharks also use vision to locate and approach prey. The research team was interested in the flexibility of this behaviour. That is, do the sharks simply identify a source of food and immediately head straight for it? Or do they use some shark-cunning and approach their upcoming snack in such a way as to maximize success (for the shark, rather than the lunch)?

The question Alex and the team wanted to answer was whether the direction with which great white sharks would approach their prey was affected by the direction of the sun. Potentially, coming out of the same direction as the sun would be a sensible strategy, since it might make it harder for the prey to see the shark, and might make the prey stand out more clearly against the dark background. However, the sun is continually shifting position in the sky and so the use of this cue would require some flexibility on the part of the shark.

So that’s a pretty interesting question – but how do you ask a shark to take part in your experiment? In this case, the team took a boat out to the cold waters off South Australia, which are known to have populations of great whites. They then attached tuna bait to a float, and essentially waited for the sharks to turn up. They didn’t have much trouble getting willing participants. In 30 days, there were almost 1000 shark visits to the bait; in the end, they classified 337 as being predatory and occurring on sunny days.

Although the approaches did occur from all directions, by far the most popular direction was when the sun was behind the shark (statistical tests were able to show that this occurred much more often than expected by chance). This was also shown by differences in approach in the morning (when the sun was in the east) and evening (when it was in the west).

Interestingly, there were big variations between different sharks. The researchers were able to identify a few sharks that came back again and again. Some of the sharks used the sun on many more approaches than others did. This shows us that different sharks seem to be using the strategy more or less.

If it was cloudy, sun direction had no effect. This is not very surprising, since it just shows that the sun doesn’t affect behaviour if the sharks can’t see it.

So great white sharks are sensitive to changing features of their environment, and are able to exploit them in order to get a meal. This work has important theoretical implications, since it helps us understand the commonalities of intelligence across species (including our own). But it also has practical importance for us, since the more we know about shark behaviour and the cues they use, the better we can design beach environments that keep them safely swimming in the deep and the us safely playing in the shallows.

For more information on Alex Taylor’s research, click here:
http://www.psych.auckland.ac.nz/people/alexander-taylor
http://alexhtaylor.com

You can find the research paper here:
http://www.jstor.org/discover/10.1086/680010?uid=3738776&uid=2&uid=4&sid=21105519120811

For a short video from Flinders University describing this study, click here:
http://mtu.flinders.edu.au/events/White_Sharks_and_the_Sun.cfm

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