Decline of top predators causing increase of smaller predators

Posted By: Staff
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Washington, October 2 (ANI): A new study has determined that the catastrophic decline around the world of "apex" predators such as wolves, cougars, lions or sharks has led to a huge increase in smaller "mesopredators" that are causing major economic and ecological disruptions.

The findings revealed that in North America, all of the largest terrestrial predators have been in decline during the past 200 years, while the ranges of 60 percent of mesopredators have expanded.

For example, in parts of Sub-Saharan Africa, lion and leopard populations have been decimated, allowing a surge in the "mesopredator" population next down the line, baboons.

"This issue is very complex, and a lot of the consequences are not known," said William Ripple, a professor of forest ecosystems and society at Oregon State University (OSU).

"But there's evidence that the explosion of mesopredator populations is very severe and has both ecological and economic repercussions," he added.

According to the researchers, in case after case around the world, primary predators such as wolves, lions or sharks have been dramatically reduced if not eliminated, usually on purpose and sometimes by forces such as habitat disruption, hunting or fishing.

Many times, this has been viewed positively by humans, fearful of personal attack, loss of livestock or other concerns.

But, the new picture that's emerging is a range of problems, including ecosystem and economic disruption that may dwarf any problems presented by the original primary predators.

The elimination of wolves is often favored by ranchers, for instance, who fear attacks on their livestock.

However, that has led to a huge surge in the number of coyotes, a "mesopredator" once kept in check by the wolves.

The coyotes attack pronghorn antelope and domestic sheep, and attempts to control them have been hugely expensive, costing hundreds of millions of dollars.

"The economic impacts of mesopredators should be expected to exceed those of apex predators in any scenario in which mesopredators contribute to the same or to new conflict with humans," according to the researchers.

"Mesopredators occur at higher densities than apex predators and exhibit greater resiliency to control efforts," they added.

At OSU, Ripple and colleague Robert Beschta have done extensive research and multiple publications on the effect that loss of redators such as wolves and cougars have on ecosystem disruption, not only by allowing increased numbers of grazing nimals such as deer and elk, but also losing the fear of predation that changes the behavior of these animals. (ANI)

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