The Ecology of Fear

Grasshoppers in fear of predation die with less nitrogen in their bodies than unstressed grasshoppers, which can affect soil ecology.

Jun 15, 2012
Edyta Zielinska

A red-legged grasshopperFLICKR CREATIVE COMMONS, ARRANET

Looking at the interplay between living organisms and the soil chemistry that in turn supports life, researchers have found that stressed insects die with less nitrogen in their bodies, providing fewer nutrients to the soil and slowing the rate of plant-matter decomposition.  The study, published last week (June 14) in Science, suggests that insect interactions and diversity can have a dramatic impact on the soil fertility, and consequently, on ecosystem health.

“We were interested in bridging two subfields of ecology—organism ecology and biogeochemistry—in a way to make predictions about how food web structure can affect nutrient cycling,” first author Dror Hawlena of the Hebrew University of Jerusalem told Nature.

The researchers housed one set of grasshoppers together with predatory spiders, which had their mouth-anatomy glued shut so that the experimental grasshoppers would not actually be eaten, while another set was housed with no spiders. When the grasshoppers died, the researchers added their decomposing bodies to soil along with leaf litter.  After 3 months, the plant matter in the soil seeded with afraid grasshoppers had decomposed 200 percent less than the plant matter in soil treated with unafraid grasshoppers.

“The traditional view is that plants and microbes are the main players linking the biotic and the abiotic world, but here we have shown that predators can actually regulate microbes by affecting the chemical composition of their own prey,” Hawlena told Nature.