Predator-Created Domino Effect Leads To Ecosystem Changes
June 17, 2012

Predator-Created Domino Effect Leads To Ecosystem Changes

Creatures that are feeling the pressure from the presence of predators are known to alter their diets, thus having a noteworthy impact on their habitats, claims new research published in the journal Science.

According to the National Science Foundation (NSF), researchers from Yale University and the Hebrew University of Jerusalem teamed up to study changes in the types of plant life consumed by grasshoppers under different circumstances.

Ordinarily, grasshoppers eat nitrogen-rich grass, which helps stimulate their growth and reproduction, but that all changes when spiders enter the picture.

Once they detect predators, the grasshoppers will switch to carbohydrate-rich plants, which alter their body chemistries towards carbon and away from nitrogen.

As a result, when a grasshopper dies, its body will decompose less rapidly, thus "depriving the soil of high-quality fertilizer and slowing the decomposition of uneaten plants," the foundation added.

"Under stressful conditions they go to different parts of the 'grocery store' and choose different foods, changing the makeup of the plant community," Oswald Schmitz, study co-author and Yale University ecologist, said in a statement.

"It only takes a slight change in the chemical composition of that animal biomass to fundamentally alter how much carbon dioxide the microbial pool is releasing to the atmosphere while it is decomposing plant organic matter," he added. "This shows that animals could potentially have huge effects on the global carbon balance because they're changing the way microbes respire organic matter."

Based on their findings, Schmitz and colleagues believe that organic matter of leaves decomposed between 60% and 200% faster in stress-free conditions versus those where predators are causing anxiety. While they said that climate and litter quality have a greater impact on the decomposition of organic matter, they claim that they have demonstrated how predators can alter how microbes help break down such material.

"What it means is that we're not paying enough attention to the control that animals have over what we view as a classically important process in ecosystem functioning," Schmitz said.

"Traditionally people thought that animals had no important role in recycling of organic matter, because their biomass is relatively small compared to the plant material that's entering ecosystems," he added. "We need to pay more attention to the role of animals, however. In an era of biodiversity loss we're losing many top predators and larger herbivores from ecosystems."