The fear large predators instill in their prey may be the glue holding ecosystems together, according to a new study. Aside from hunting prey, and therefore controlling population size, large carnivores paint what researchers call a "landscape of fear," inhibiting prey from feeding and restricting them to designated areas only. It is believed that this sense of "fear" can facilitate cascading effects down the food chain.
In the latest study, researchers from Canada's Western University and Simon Fraser University played threatening sound recordings of large carnivores over speakers. In this case it was the sound of barking domestic dogs, which are the main predators of raccoons on the Gulf Islands of British Columbia, Canada. To compare, researchers also played the calls of seals and sea lions, which also live on the islands but are not a threat to raccoons.
Overall, researchers found the dog sounds cut the raccoons' foraging time by 66 percent over the course of a month. As a result, this also triggered an increase of crabs, fish and worms that raccoons generally feed on in the intertidal areas.
"These results have critically important implications for conservation, wildlife management and public policy," Liana Zanette, a wildlife ecologist from Western University, said in a news release. "We have now experimentally verified that, by instilling fear, the very existence of large carnivores on the landscape -- in and of itself -- provides an essential 'ecosystem service,' and failing to consider fear risks dramatically underestimates the role large carnivores play in structuring ecosystems."
Large carnivores are feared by many, including humans. This is why conservation actions -- like the reintroduction of wolves to Yellowstone National Park -- are viewed as controversial, and why the need to prevent animals like deer, coyotes and raccoons from eating everything in sight is often overshadowed by humans' need for safety, as larger animals have a reputation for being violent.
"We've succeeded in wiping out large carnivores in most of the globe, and we're only now beginning to understand the ecological consequences," Ph.D. student Justin Suraci, one of the study authors from Simon Fraser University, added. "The real message here is that we need large carnivores."
Their findings were recently published in the journal Nature Communications.
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