Fish can scare insects to death!

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Fish have the power to scare some insects to death, a new study has found.

The work by biologists at the University of Toronto found that the stressed placed on dragonflies exposed to predatory fish often resulted in their death.

The team raised juvenile dragonfly larvae (Leucorrhinia intacta) in aquariums or tanks along with their predators.

The two groups were separated so that while the dragonflies could see and smell their predators, the predators could not actually eat them. They found that larvae raised together with predatory fish had survival rates 2.5 to 4.3 times less than those not exposed.

When allowed to progress to metamorphosis it was found that dragonflies exposed to fish were over five times as likely to die compared to those 'fish free'.

Professor Locke Rowe, chair of the Department of Ecology and Evolutionary Biology said: "How prey respond to the fear of being eaten is an important topic in ecology, and we've learned a great deal about how these responses affect predator and prey interactions."

"As we learn more about how animals respond to stressful conditions – whether it's the presence of predators or stresses from other natural or human-caused disruptions – we increasingly find that stress brings a greater risk of death, presumably from things such as infections that normally wouldn't kill them," says Rowe.

For more information see: Shannon J. McCauley, Locke Rowe, Marie-Josée Fortin.The deadly effects of 'nonlethal' predators. Ecology, 2011; 92 (11): 2043 DOI: 10.1890/11-0455.1

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