Tiny Fake Caterpillars Uncover Strange Global Predation Pattern
Thousands of dummy caterpillars played a huge role in identifying the global trends of predation on insect herbivores.
According to a report from the University of Oxford, the experiment revealed that predatory behavior in the tropics is determined not by birds or mammals but by ants and other small arthropods. The international team observed a fraction of caterpillars eaten from the Arctic Circle to southern Australia and found that a caterpillar near the equator is eight times more likely to be eaten than one at the poles.
The study involved the researchers gluing thousands of fake plasticine caterpillars to plants in 31 different sites across the world. A total of 2,879 were distributed and left at the sites for four to 18 days. Predators such as birds and ants take a bite before realizing it's a dummy and moving on.
"Tomas had used plasticine caterpillars in Greenland and thought they didn't work when he found very low attack rates," one of the lead authors Dr Eleanor Slade of the Universities of Oxford and Lancaster said. "I had used them in Borneo, and detected very high attack rates. Just imagine if these are the two end points of a global pattern, we thought. And that is exactly what they turned out to be."
Slade also said that the dummy caterpillars were able to tell them the type of predator that attacked with the bite marks.
"People often think of vertebrates as the most important predators in the tropics, but birds and mammals weren't the groups responsible for the increase in predation risk towards the Equator," ETH Zurich postdoctoral research associate Dr Will Petry, who contributed data and supported analysis from California, pointed out. "Instead tiny arthropod predators like ants drove the pattern."
The study was published in the journal Science.