This moth caterpillar might have one of the best disguises in nature. It looks like a pile of bird poop! While resting on branches or leaves, the caterpillars curl up to resemble bird droppings. They use the trick to hide from predators like birds.

Many animals use camouflage to blend in with their surroundings. Coloring and body shape can all be part of the trickery. The moth caterpillars’ disgusting disguise is a type of camouflage called masquerade. “Masquerade is a defense that makes prey resemble inedible objects such as bird poo, stones, or twigs,” says Toshitaka Suzuki, a biologist at the Graduate University for Advanced Studies in Japan. 

Suzuki found that the caterpillars’ curled pose was the key to fooling hungry birds. He and his research partner made more than 400 fake caterpillars out of pastry dough and placed them in cherry trees. Their fake caterpillars were either green or poop-colored, and their “bodies” were either curled or straight. 

In real life, poop-colored caterpillars curl at rest, but those with other coloration are typically straight when resting. For the green caterpillar replicas in Suzuki’s study, posture didn’t affect the number of attacks by birds. However, straight poop-colored replicas were three times as likely to be attacked by birds as those that were curled up. Without the poop-like pose, the fake caterpillars’ cover was blown.

In nature, caterpillars masquerading as bird poo can’t rest all the time, though. They need to straighten their bodies to eat, says Suzuki. “Some caterpillars with bird-dropping coloration keep a resting posture during daytime, when predators are active, and then eat leaves at night.”