Fear affects predator-prey relationship: study

Dec 08, 2011

(PhysOrg.com) -- Franklin D. Roosevelt famously warned the only thing we have to fear is fear itself. New research from The University of Western Ontario reveals that FDR’s rhetorical flourish also accurately reflects a fundamental truth within the animal kingdom too.  

In a study published in Science, findings from a team led by University of Western Ontario biology professor Liana Zanette prove perception – in this case, – of predation risk is powerful enough to affect wildlife populations even when are prevented from directly killing any prey.

“The traditional view of predators is that they kill prey, and that direct killing is the only way predators can affect prey numbers,” says Zanette, a principal investigator at Western’s Advanced Facility for Avian Research. “But predators also scare prey and wildlife live with this fear of being torn limb from limb by some predator every moment of every single day of their entire lives. This state of fear can be as important as direct killing in reducing prey numbers.”

The ground-breaking research was conducted on song sparrows nesting in British Columbia’s southern Gulf Islands. The researchers first protected every song sparrow nest from predators by surrounding them with netting and electric fences.
The researchers then played different sounds to different groups of birds throughout the four-month breeding season. One group heard sounds associated with their natural predators while the others heard non-threatening natural sounds. 

Zanette and the team discovered that the birds that heard the predator sounds produced 40 per cent fewer offspring. Such large reductions in numbers due simply to the sound of fear, unambiguously show for the first time in any wild bird or mammal that predators do significantly affect the population sizes of their prey not just by killing prey, but by scaring them as well.

“This has important implications for conservation and wildlife management because it suggests that the total impact of predators on populations will be underestimated if the effect of fear itself is not considered,” adds Zanette. “This means that the adverse effects of introduced predators are likely worse than previously imagined and the disturbance to native ecosystems due to the loss of native predators has probably been greater than we previously thought.”

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not rated yet Dec 08, 2011
"The ground-breaking research was conducted on song sparrows nesting in British Columbias southern Gulf Islands. The researchers first protected every song sparrow nest from predators"

Are they really saying that they protected every, sparrow nest. The article does not tell us much about the specifics of the the experiment (including sample size). Also, the results are from a singular experiment and we do not even no if there were any others. This leaves the claims with little to no evidence. Why even post this story?
not rated yet Dec 09, 2011
"The ground-breaking research was conducted on song sparrows nesting in British Columbias southern Gulf Islands. The researchers first protected every song sparrow nest from predators"
What so fundamental about it? The 11th-century Persian doctor Avicenna placed the lamb and wolf into neighbouring cages and the lamb died soon for stress. This experiment is quoted in all psychology textbooks about stress of work in cubicle environment. Why do we pay for trivial re-search again and again?

Apparently, when civilization and volume of its information grows sufficiently, then the researchers can repeat the same experiments again and again, because these older ones are simply forgotten well before they can be used.
not rated yet Dec 09, 2011
I think that it has already been shown that at least some birds are choosy about nesting in a "good area", so the reduced breeding may be a rational policy of the birds not to waste their breeding effort if their area suddenly turns "bad" after they've made a nest, rather than being a direct fear effect. If they had had the choice, they might not have made a nest in that area in the first place.

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