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Wild Things

The weird and wonderful in the natural world
Sarah Zielinski
Wild Things

Dazzle camouflage may fool a locust

During World Wars I and II, some U.S. and British naval vessels, such as the U.S.S. Nebraska, shown here in 1918, were painted in a type of camouflage known as dazzle painting. Though evidence is scant that humans are fooled by the camouflage, a new study suggests that dazzle patterns do confound locusts.

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The guys who painted American and British naval ships with bold, black-and-white patterns during World Wars I and II probably thought their commanders were nuts. But the idea behind this dazzle camouflage wasn’t completely crazy. The thinking was that the complex patterns would make it more difficult for an enemy to estimate the ship’s size, type, speed and heading, thus making the ship harder to hit with a torpedo.

Though scientists are still on the fence about whether humans are truly tricked by such striking paint patterns, there is some evidence that the ships’ painters might have been right: A study published earlier this year in PLOS ONE, for example, found that in a computer game, an object’s striped patterns disrupted players’ perception of speed and their ability to hit the object.

Dazzle markings can also be found in nature, seen as bands or zigzags on animals such as snakes, fish, invertebrates and, perhaps, even zebras. These patterns are often thought to protect a creature from a predator, but they might also conceal a predator from its prey, says Roger Santer, a zoologist at Aberystwyth University in Wales. Santer recently set out to test whether such markings could dazzle the locust Schistocerca gregaria. His study was published December 3 in Biology Letters.

Santer’s experiment began in a strikingly similar way to the method used to test dazzle camouflage on humans — with a locust parked in front of a computer screen. Santer inserted copper wires into the heads of his test locusts to monitor the activity of neurons connected to the insects’ vision. He then showed each locust a series of squares. Each square would rapidly expand to look like it was coming at the locust. Some of the squares were split in two, with one half bright and the other dark.

The visual neurons responded more weakly to the split squares than the solid dark ones, Santer found. With the solid squares, the locusts see something coming toward them. But with the split light-and-dark squares, they get competing messages, seeing the dark bit as something approaching and the light half as something moving away. Confused, the locust’s visual neurons respond at a lower rate, indicating that they themselves are dazzled, Santer says. These “results demonstrate that dazzle patterns can decrement looming motion perception,” Santer writes.

That said, dazzle camouflage may not be the best kind of camouflage in nature, Santer admits. He notes that cuttlefish, which can control the patterns of colors that appear on their skin, choose to reduce high-contrast color elements when on the move; it’s better for them to blend in.

And the jury is still out on whether the dazzle patterning put on ships in the early 20th century was really the best choice. “For humans, contrasting patterns make translating targets difficult to capture, but low-contrast uniform targets are still harder to capture,” Santer writes. However, one of the reasons behind the choice of the bold painting was that the variety of weather conditions that the ships sailed through was too varied to make any one color a good choice for low-contrast camouflage. Even if the dazzle paint was less effective, it would have worked rain or shine.

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