‘Dummy caterpillars’ reveal global predation patterns

May 18 (UPI) — If you’re an insect trying to not get eaten, head the opposite direction of the equator.

New research suggests predator-prey interactions are more common near the equator than near the poles. The global predation pattern was revealed by an analysis of bite marks left in tiny green “dummy caterpillars.”

The bright green dummy worms were carved from plasticine, a type of modeling clay, by researchers at the University of Helsinki and distributed to scientists around the world. The dummies were systematically adhered to leaves at a full range of latitudes and elevations all over the globe.

After a period of exposure, the caterpillar dummies were mailed back to Finland, where scientists tallied and analyzed the bite marks left by the pinchers and beaks of hungry predators.

“The great thing about this method is that you can track down who the predator was by inspecting the attack marks,” Eleanor Slade, a researcher at the University of Oxford, said in a news release. “The jaws of an insect, like an ant, will leave two small piercings, whereas a bird beak will cause wedge-shaped marks. Mammals will leave teeth marks — well, you get the idea.”

When researchers compared the rates of predation at different latitudes, they found a caterpillar at the equator was eight times more likely to be preyed upon than a caterpillar close to the poles.

“What was most fascinating was that the pattern was not only mirrored on both sides of the equator, but also appeared across elevational gradients,” said study leader Tomas Roslin. “Moving up a mountain slope, you find the same decrease in predation risk as when moving towards the poles. This suggests a common driver could be controlling species interactions at a global scale.”

Researchers say their findings — published in the journal Science — are a reminder of the scientific potential of collaboration.

“As ecologists, we typically ask questions about patterns and processes much larger than we as single researchers or teams can examine,” said researcher Bess Hardwick. “But by designing experiments that can be split into smaller work packages, we can involve collaborators all over the world, and work together to understand the bigger picture.”