Bird dropping disguise proves to be effective camouflage

orb-web spiders and webs

SPIDER OR BIRD POOP?  The first and third rows show examples of bird feces found in a forest in Taiwan. Rows 2 and 4 are orb-web spider (Cyclosa ginnaga) web decorations from the same area.

Min-Hui Liu/National Chung-Hsin Univ.

As people who have owned both dogs and cats have probably realized, some dogs have no qualms about eating feces. But most critters will leave dung alone, and that makes camouflaging yourself as someone else’s poop nearly a perfect disguise.

Take the orb-web spider Cyclosa ginnaga, for example. This species uses its silver body and white, blotchy web decorations to masquerade as bird droppings, Min-Hui Liu of National Chung-Hsin University in Taichung, Taiwan, and colleagues report May 29 in Scientific Reports. The camouflage is good enough to fool predatory wasps. When the researchers colored the spider and its web decorations black, the spiders were subject to more wasp attacks.

The finding was the first to suggest that web decorations “might be used to form part of a bird dropping masquerade to avoid predators,” the researchers noted. But it was not the first time anyone had found an animal that disguised itself as dung. Here are some other examples of animals using the façade of bird feces to hide out:

Bird dropping spiders: Cyclosa ginnagamay have been the first-known spider to use its web to help it look like bird poo, but there are several other species can do that without any webby assistance. Celaenia escavata, a.k.a. the bird-dropping spider, from the eastern and southern coasts of Australia, is often hanging out in orchards and looks like one of the local birds may have excreted it. Some species of Mastophora spiders are also thought to mimic bird droppings. And then there’s the bird-dung crab spider (Phrynarachne sp.) of Singapore. Some of those spiders not only look like dung, but they also produce an odor that smells like feces or urine. Their camouflage may serve a purpose other than predator protection, though — the smell may attract flies for the spiders to eat.

Asian swallowtail caterpillar: Long before Asian swallowtails (Papilio xuthus) grow up to be beautiful black-and-white butterflies, and before they take on the appearance of fat, green leaves, the young caterpillars looks like little logs of bird poop. The change in form from bird dropping to green leaf relies on only three genes, researchers at the University of Tokyo reported in Science in 2008. By applying a hormone that regulates those genes to the back of young caterpillars, the scientists discovered they could make big caterpillars that look like feces.

Pied warty frog: This frog (Theloderma asperum), found in China and Southeast Asia, is colloquially knows as the “bird poop frog.” Not much is known about the tiny frog, which is just a few centimeters long and lives in water-filled tree cavities. But the species is thought to be on the decline due to the loss of its forest habitat. Given that, it seems that people purchasing wild-caught bird poop frogs as exotic petsmight want to rethink their pet choice. Besides, who really wants to own something that looks like poo?

Sarah Zielinski

Sarah Zielinski is the Editor, Print at Science News Explores. She has a B.A. in biology from Cornell University and an M.A. in journalism from New York University. She writes about ecology, plants and animals.

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