Monday, June 25, 2007

Fear of predators is learned behavior, study says

By Ed Stoddard
Thu Jun 21, 2:41 PM ET

DALLAS (Reuters) - Fear of predators is not instinctive but is a learned behavior that only develops when prey species share space with animals that eat them, according to a new study released this week.

The study's conclusion: remove the lions, and the zebras will lose their fear of them. But add wolves to a new territory and the resident elk or moose will soon learn they spell trouble.

Conducted by Dr. Joel Berger of the Wildlife Conservation Society, or WCS, the study compared the behavior of four prey species in three different settings: locations where predators still prowled; areas where top predators no longer exist; and places where carnivores had been reintroduced.

Such research is regarded as important to understanding the dynamics of reintroducing predators to ecosystems where they had been exterminated by humans.

"If you take away wolves, you take away fear. That is a critical piece of knowledge as biologists and public agencies increase efforts to re-introduce large carnivores to places where they have been exterminated," WCS said in a statement.

"When the predator-prey relationship comes back into balance, impacts ripple through the system. For example, when wolves returned to the Yellowstone region, they caused a cascade of events including a change in elk distribution, more wariness in moose, and a change in coyote densities," it said.

Wolves were re-established a decade ago in Yellowstone National Park in the western United States.

Berger tested reactions of animals living without their historic predators by playing recordings of wolves and tigers.

"As expected, in the absence of predators, the elk, moose, bison and caribou did not show the kind of vigilance, clustering behavior and flight observed in the same species living with wolves, bears or tigers," the WCS said in a statement.

"For example, elk in the mountains of Siberia -- who subsist alongside tigers, wolves and bears -- responded five times faster to the recordings than did elk in Rocky Mountain National Park (Colorado) where major predators have been absent for some 90 years," it said.

The study adds to previous work such as that on the evolution of flightlessness in birds on islands without predators. Such birds were often exterminated after the arrival of humans in part because they had no fear of predators.

The study is published in the latest issue of the journal Conservation Biology.

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