TORONTO, Oct. 27 (UPI) -- The mere presence of a predator can stress a dragonfly enough to kill it, even if the predator can't actually get at it to eat it, Canadian researchers say.
The scientists suggest their findings could apply to all organisms facing any amount of stress.
"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," University of Toronto evolutionary biologist Locke Rowe said.
In an experiment, juvenile dragonfly larvae were raised in aquariums. Some were raised alone, and others were raised in tanks where they could see and smell their predators, although the predators could not actually eat them.
"What we found was unexpected -- more of the dragonflies died when predators shared their habitat," Rowe said.
Larvae exposed to predatory fish or aquatic insects had survival rates 2.5 to 4.3 times less than those not exposed, he said.
And subsequently, 11 per cent of larvae exposed to fish died as they attempted to metamorphose into their adult stage, compared to only 2 percent of those growing in a fish-free environment.
"We allowed the juvenile dragonflies to go through metamorphosis to become adult dragonflies, and found those that had grown up around predators were more likely to fail to complete metamorphosis successfully, more often dying in the process," Rowe said.
