Fear is a horrible thing, and new research suggests that its effects can extend even beyond death. In a field experiment, scientists raised red-legged grasshoppers (Melanoplus femurrubrum, image), a North American species, in the presence of predatory spiders (Pisaurina mira, the nursery web spider, inset). Analyses revealed that the fear-addled grasshoppers ended up with a higher carbon-to-nitrogen ratio in their bodies than the presumably stress-free insects raised without spiders -- largely because their constantly amped-up metabolism obliged them to burn nitrogen-bearing protein to generate energy-providing glucose. The lower amounts of nitrogen in the carcasses of fearful grasshoppers didn't affect how quickly they decomposed in soil after death, but it did substantially slow down the decay of leaf material later added to the soil , the researchers report online today in Science. That slowdown, in turn, likely stems from the decreased efficiency of soil microbes and fungi, which need nitrogen to perform their decomposition duties. Because the metabolic changes triggered by fear are likely common to all prey species, the new findings reveal a new way that animals—both predators and prey—influence the cycling of nutrients through ecosystems.
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