WASHINGTON - Like many online video games, the one developed by scientists at the University of Exeter challenges players to quickly find hidden objects, but with a twist. They're not looking for gold or swords or magical mirrors in an imaginary universe, but for birds in real photos. And everyone who plays "Where is that Nightjar" is contributing to a study of animal vision.
Nightjars are ground-nesting birds, whose mottled feathers help them disappear into the fallen leaves and twigs where they lay their eggs. They are hunted by a variety of predators and rely on their camouflage for their survival.
Some predators, such as mongooses, are color-blind and cannot see reds and greens. They are called dichromats. Others, like baboons and humans, are trichromats, and can see a wider range of colors. Researchers wanted to know how color vision affected an animal's ability to find camouflaged prey.
"A huge number of mammals are dichromats," ecologist Jolyon Troscianko explains. "But it does not take a huge evolutionary leap to develop this third color channel. So it is surprising that this has not happened more often in nature, suggesting there could be some advantage to being a dichromat."
The game uses actual photos of nightjars, manipulated so the images appear as they would through the eyes of a dichromat predator, and also as we would see them. People could choose to play as a trichromat or a dichromat, and they had just 30 seconds to try to find each camouflaged bird.
After 30,000 volunteers played the game, the researchers got some surprising results, published in Behavioural Ecology.
Scientists assumed that dichromats, which are better at differentiating between light and shadow, would be better at finding camouflaged prey. But the trichromat competitors found the birds and their eggs faster, at first. Troscianko says as the game progressed, the dichromats improved faster, and were performing equally well by the end of the game.
"That shows that there is a huge element of learning, which has previously been largely ignored in the importance of camouflage. But if a predator in the wild is learning to try to find one type of prey, one type of camouflage faster than another, that could actually change the whole dynamics of an ecosystem where there is now a disadvantage to having a camouflage type that is easily learned by predators over time."
The Exeter Sensory Ecology Group has also developed games to study camouflage in other animals, like crabs and moths.