EUGENE, Ore. -- (Dec. 9, 2010) -- When their razor-sharp mandibles wear out, leaf-cutter ants change jobs, remaining productive while letting their more efficient sisters take over cutting, say researchers from two Oregon universities.
Their study -- appearing online ahead of regular publication in the journal Behavioral Ecology and Sociobiology -- provides a glimpse of nature's way of providing for its displaced workers.
"This study demonstrates an advantage of social living that we are familiar with -- humans that can no longer do certain tasks can still make very worthwhile contributions to society, even if they could not live on their own," said the paper's lead author Robert Schofield, a scientist at the University of Oregon. "While division of labor is well documented in social insects, this is the first suggestion that some social insects stop performing certain tasks because they are no longer as good at them as they used to be. As social organisms, these ants have the luxury of being able to leave the cutting task to their more efficient sisters."
Leaf-cutter ants slice leaves, carry pieces back to the underground nest for further processing and, like tiny mushroom farmers, grow an edible fungus on the resulting substrate. The ants doing the cutting are usually members of the generalized forager caste, one of four size-based behavioral castes of workers. The foragers are second in size to the majors, the large workers that protect the colony and do heavy clearing work on the trails constructed to connect the nest to the leaf sources. In addition to cutting, the foragers transport the cuttings, scout for new resources and also help protect the colony.
"Cutting leaves is hard work. Much of the cutting is done with a V-shaped blade between teeth on their mandibles that they use like a tailor who holds a pair of scissors in a fixed V shape to slice through cloth," Schofield said. "This blade starts out as sharp
|Contact: Jim Barlow|
University of Oregon