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Thursday, December 16, 2010

Leaf cutter ant blades

Researchers from the University of Oregon and from Oregon State University have been studying the leaf cutter ants Atta cephalotes. In doing so, they’ve made two interesting discoveries. One is that the tiny creatures have incredibly sharp and durable cutting blades on their mandibles. The second is that the ants have a retirement program for older workers.

Leaf cutter ants make their living by cutting up leaves and carrying them back to their nests. The ants don’t eat the leaves, rather, they use the leaves to feed a crop of fungus which the ants actually eat. Yes, leaf cutter ants are tiny farmers. It takes a lot of effort to slice through those thick leaves (in comparison to the ants) and a sharper slicing blade makes the job that much easier. Robert Schofield, lead author of the paper in Behavioral Ecology and Sociobiology, and his team have found that the slicing blade on the ants mandibles is made of a zinc-rich biomaterial that starts out as sharp as any man-made knife edge. These biomaterials have been found in the sharp parts (stings and claws) of other small invertebrates.

You can watch some leaf cutter ants at work below.

Even this sharp, durable substance does get dull over time, and the ants have no way of sharpening them. The video below shows an ant with a dull cutting blade. Notice how inefficient the ant is at cutting through the leaf.

Once the ants are taking three times as long to cut the same number of leaves, they retire from leaf-cutting and become leaf carriers. Their new job is to carry the leaf pieces back to the nest. Thus, they continue to perform useful tasks even after they are too old to continue at their previous jobs.