Lacking the presence of wolves or other main predators in both terrestrial and marine environments, populations of smaller predators have greatly increased. Other studies have documented mesopredator impacts on everything from birds to lizards, rodents, marsupials, rabbits, scallops and insects. This includes much higher levels of attacks by coyotes on some ranch animals such as sheep, and efforts attempting to control that problem have cost hundreds of millions of dollars.
Scientists have concluded that exploding mesopredator populations can be found in oceans, rivers, forests and grasslands around the world.
"In the absence of wolves, coyote densities and distributions generally expanded in the U.S., into the Midwest, to the northeast as far as Newfoundland, and as far northwest as Alaska," the researchers wrote in their report.
Where wolves recovered, as in Yellowstone National Park, coyote populations were initially reduced by 50 percent, Ripple said. Although more sampling will be required, early evidence indicates that a snowshoe hare recovery may be taking place.
As these issues are factored into decisions about how to manage wolves, the researchers said, it's also important to maintain what they call "ecologically effective" wolf populations, the researchers wrote in their study. The full value of these top predators, and the numbers of them it takes to achieve a wide range of ecological goals, should be more thoroughly researched and better understood, they said.
|Contact: William Ripple|
Oregon State University