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Prey not hard-wired to fear predators

June 21, 2007

Are Asian elk hard-wired to fear the Siberian tigers who stalk them" When wolves disappear from the forest, are moose still afraid of them?

No, according to a study by Wildlife Conservation Society scientist Dr. Joel Berger, who says that several large prey species, including moose, caribou and elk, only fear predators they regularly encounter. 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. Berger's study is published in the latest issue of the journal Conservation Biology.

The goal of re-introduction isn't simply to save a species; it is to restore the natural functions of wild places. 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. By contrast , where wolves and grizzly bears were lost, migratory birds including warblers and hummingbirds were less abundant because moose over-browsed vegetation used by these migrants. "It is not just changes in climate or disease may alter our big remote wild landscapes, but so do the actions of conservationists and public agencies by restoring ecosystems to bring native carnivores back to where they once thrived." said Dr. Berger.

Berger's study, which looked at 19 areas including the Russian Far East, Greenland, Canada, and the U.S., demonstrated that caribou, elk, and moose are all affected by both the loss and return of their predators in ways that are important for conservation and ecosystem integrity.

These findings come at a time when, after more than $23 million was spent to re-establish wolves in the northern Rocky Mountains, the animals are to be down-listed from federal protection. The states of Wyoming and Idaho have already proposed plans that would allow for as much as 85 percent of these once-protected wolves to be killed. So even as the goal of re-instilling fear of predators in prey species has been successful, the question remains whether enough wolves will be left to maintain the larger goals of natural function and balance, according to Dr. Berger.

Notes on the Study

The study compared the behaviors of four species of prey animals in three different prey situations:

* Locations were native predators still exist. (Eastern Siberia, Boreal Canada and Alaska)

* Locations where the top predators no longer exist. (the polar islands of Greenland and Svalbard, Norway)

* Locations where native predators have been re-established after once being extinguished. (Yellowstone and Grand Teton National Parks )

To test reactions of animals living without their traditional predators, Berger played recordings of wolves and tigers and chronicled their reactions. 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. 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.

Wildlife Conservation Society