Caterpillars contort their bodies to look like bird poop
Toshitaka Suzuki

Caterpillars contort their bodies to look like bird poop

How to ward off hungry birds if you're a tasty caterpillar? Try to look like something really distasteful: bird poop. Some caterpillars are masters of disguise, fine-tuning their poo mimicry with a grab bag of tricks—using color, pattern, choice of resting place, and, sometimes, contorting their bodies to match the squiggly shape of bird droppings. In a paper published online this month in Animal Behaviour, scientists used artificial edible caterpillars created from pastry dough to see if a bent shape made birds less likely to gobble them up. The replicas resembled moth larvae Apochima juglansiaria, shown above, and Macrauzata maxima, both of which masquerade as bird droppings. They pinned the models on cherry trees, the natural habitat of moth larvae, bending some into squiggles while keeping others straight. Birds attacked the bent ones almost three times less often than the straight ones. When the researchers performed the same experiment with green caterpillars that do not mimic bird droppings, there was no difference in attack rate between the bent and unbent models. This is the first experimental demonstration of how posture can help caterpillars masquerade as inedible objects.