We already know that great whites use their remarkable set of senses to track down prey, but it turns out they also use something else to their advantage: the sun. According to new research, these animals exploit the angle of the sun’s rays when hunting, possibly because it improves camouflage. Interestingly, this could be the first known example of a non-human animal using the sun as part of its hunting strategy.
Although we know that great white sharks are not quite the mindless man-eaters "Jaws" would have you believe, they are highly evolved predators. Sitting comfortably at the top of the marine food chain, they have no natural predators of their own and are equipped with an impressive set of features that collectively make them the skilled hunters that they are. Their streamlined, torpedo-shaped bodies and powerful tails allow them to propel through the water at speeds of up to 35 miles (50 km) per hour, which is fast enough for them to burst out of the water entirely.
But great whites are far more than just straight-up brawn: their brains have to coordinate all of their highly-developed senses, such as olfaction (smell) that allows them to sniff out one drop of blood in 100 liters of water, or a seal colony two miles away. They even have special sensing organs that allow them to pick up electrical signals generated by animals, for example by their beating hearts.
While these animals have been documented attacking during the day, they tend to focus their hunting at dawn and dusk. Scientists believed that this was likely due to the fact that the sun is unable to penetrate deep into the water during these times and thus increases camouflage, but researchers wanted to probe this idea further and investigate whether the sun’s position on the horizon plays an important role in their hunting strategy.
To find out more, scientists from Flinders University set out to the sea off the southern coast of Australia and began enticing the animals towards their boat using stinky ground-up fish bits, colloquially known as “chum.” They then tossed in huge chunks of tuna attached to a rope as bait and observed how they approached it.
As described in The American Naturalist, they documented 44 different great whites making an impressive total of 1,000 advances, although only 37 were actual attacks. From these data, they quickly saw a pattern emerge: Sharks tend to beeline along the direction of the sun, positioning it directly behind them. At dawn, they usually approached from the east, but at dusk they came in from the west. Interestingly, they also found that when the sun’s rays were obscured by clouds, they had uniformly distributed approach directions, which further suggests that they are exploiting the fluctuating sun during predation.
As pointed out by New Scientist, there are likely a number of reasons that the sharks are doing this. For example, it could avoid overstimulation of the retina, or possibly make them more difficult to spot by prey hanging around at the surface because they are concealed by the glare reflecting off the water. Alternatively, it might be that prey is better illuminated at these angles, but ultimately it’s likely to be a combination of factors.
