麻豆传媒

The best-hidden creatures wear high-vis outfits (Image: Jim Richardson/National Geographic Creative)

For animals like zebras, being conspicuous is the best way to avoid becoming dinner. New research shows how it helps soldiers and citizens hide in plain sight

TO BECOME invisible, first make yourself conspicuous. It sounds absurd, especially once you learn that this concept was the brainchild of an eccentric American artist. Now, more than a century after it was put forward, the idea is finally being tested. The findings have revealed surprising insights into how camouflage fools 鈥� or fails to fool 鈥� the eye of the beholder.

In 1909, the prevailing belief was that animals hid themselves by matching their surroundings. Then the painter and naturalist Abbott Handerson Thayer suggested a different mechanism was at work: highly conspicuous markings, such as the zebra鈥檚 stripes and the oystercatcher鈥檚 black-and-white plumage, are actually disguises. Predators, he reasoned, locate their prey by looking for their outlines, so animals with high-contrast markings that disrupt telltale edges and create false ones can evade detection.

With this and other ideas about animal markings, Thayer earned himself the title 鈥渇ather of camouflage鈥�. But although disruptive camouflage was cited in countless textbooks, it remained largely untested until 2005, when Innes Cuthill, Martin Stevens and their colleagues at the University of Bristol, UK, devised an experiment using fake moths made from paper triangles. By pinning them to oak trees, the researchers found that 鈥渕oths鈥� with black markings on their edges were less likely to be attacked by birds than those with central markings or uniform colours. 鈥�,鈥� says Stevens, now at the University of Exeter, UK. Using a similar approach, he and Cuthill later discovered that high-contrast markings become less effective once their contrast exceeds that in the creatures鈥� natural environment. One way to avoid this is for .

Cuthill and Stevens revived interest in disruptive camouflage, but . Richard Webster at Carleton University in Ottawa, Canada, asked volunteers to search for virtual moths on a computer screen while an eye-tracker monitored their gaze. 鈥淲e could almost get inside people鈥檚 eyes,鈥� he says. He found that the more patches moths had on their edges, the more often volunteers failed to notice them, and they needed to fixate their gaze on them for longer to have any chance of spotting them. The eye-tracking vindicated Thayer again: by breaking up an animal鈥檚 outline, disruptive camouflage does impair a predator鈥檚 ability to spot its prey.

Although instructive, the experiment had an obvious shortcoming: humans do not prey on moths, let alone computer-generated ones. To test whether disruptive colouring fools its intended audience, Stevens has started field trials. In Zambia and South Africa, his team is studying ground-nesting birds that rely on disruptive camouflage, including nightjars and plovers. His team measures the patterns on the birds鈥� feathers to quantify how well hidden they are in their environment. They also track the birds鈥� survival to determine how effectively they evade predators.

Nightjars and plovers are difficult to spot in the first place, so the researchers have employed sharp-sighted local guides to help find them. This raises the question of whether predators, like the guides, might be less easily fooled by disruptive markings as they become more familiar with them. Last year, Stevens and his team found that , especially if they see several at the same time. He suspects that the volunteers learn to stop the futile search for outlines, and instead start scanning for the high-contrast markings.

Whether non-human predators adopt the same tactic is hard to say. They may not even see camouflage markings in the same way that we do. But if predators can learn to see through disruptive camouflage, it would suggest that this concealment strategy is more likely to evolve in prey that face short-lived or generalist predators than long-lived or specialist ones.

Another open question is whether one disruptive pattern might work in a variety of environments. Webster found that camouflage can fool humans even when the colours do not match the background, provided they are not too garish. 鈥淎 jester鈥檚 costume is highly disruptive, but he鈥檚 always going to stand out,鈥� he says. Perhaps that explains the British army鈥檚 recent decision to replace its long-standing woodland and desert camouflage patterns with a single 鈥渕ulti-terrain pattern鈥� that includes green, brown and sandy yellow, following field trials indicating this print was better at concealing soldiers. 鈥淐ynics may say this is just a cost-cutting exercise,鈥� says Webster. 鈥淏ut maybe they鈥檝e worked out how to get the most out of disruptive colouration.鈥�

In fact, the military has a long history of using conspicuous patterns to fool observers. During both world wars, several US and British ships were painted with striking black-and-white geometric patterns. Some looked like floating checkerboards, others like Cubist zebras. Rather than hiding the vessels, these gaudy designs, known as 鈥渄azzle camouflage鈥� in the UK and 鈥渞azzle-dazzle鈥� in the US, were supposed to make it harder for the enemy to judge a ship鈥檚 speed, size and bearing. There was scant evidence to support the idea, so . He found that people consistently underestimated the speed of on-screen dazzle patterns, such as checks and zigzags, by around 7 per cent 鈥� but only when the patterns moved quickly. Large warships are probably too slow to benefit from this 鈥渕otion dazzle鈥� illusion, he concludes, but it could allow a speeding Land Rover to evade enemy fire. Conspicuous markings might, likewise, help a fleeing zebra elude a pursuing lion.

The army is not alone in wanting to exploit Thayer鈥檚 insights. Governments鈥� efforts to keep an eye on their citizens are changing rapidly, and this year , run by the US intelligence community, will start collecting photographs from social media websites and public video feeds, to identify faces in the images by using algorithms that match them to those on existing web profiles. Face recognition could also feature in drones, which are set to become a common feature outside war zones. Alarmed by the steady rise in surveillance, aims to thwart facial recognition technologies by being conspicuous. The bold make-up and bizarre hairstyle showcased in his project are certainly eccentric; whether they can foil an AI system is another matter. But it鈥檚 tempting to think that Thayer would have approved.

鈥淏old make-up and bizarre hairstyles might thwart facial recognition鈥�

Fool your eyes some more in our gallery: 鈥�Invisible: Animals and machines hiding in plain sight鈥�

Read more: 鈥�The invisible issue: The world as you don鈥檛 see it鈥�

This article appeared in print under the headline 鈥淩azzle dazzle 鈥檈m鈥�