Environmental reporter Josephine Marcotty writes about our place in nature through her coverage of the outdoors, wildlife, pollution and sustainability.

Who's on top shifts the balance of nature

Posted by: Josephine Marcotty Updated: August 30, 2011 - 5:23 PM

 

The return of wolves to northern Minnesota may be bad for the coyote, good for the endangered Canada lynx, and most likely a wash for the snowshoe hare. Because they all eat the hare.

That's how it works in the balance of nature, according to a new study published this week by researchers from Oregon State University. 

 

 

 

 

Photo by Ron Moen, courtesy of the Natural Resources Research Institute at the University of Minnesota

 

The decline of the Lynx has been linked to the disappearance of snowshoe hares -- the primary food for Lynx. What happened to the hares? The coyotes eat them. Why do we have so many coyotes in Edina and throughout most of the state? When wolves disappear, coyotes thrive. It's what scientists call ad "trophic cascade" that completely realigns an ecosystem. It happens all over the world, with all kinds of animals.

When the top of the food chain, in this case wolves, disappear then secondary predators called "mesopredators" take their place. In this case, coyotes.

“The increase in mesopredators such as coyotes is a serious issue," said William Ripple, a professor in the Department of Forest Ecosystems and Society at OSU, and the author of the study that appeared today in the Wildlife Society Bulletin. "Their populations are now much higher than they used to be when wolves were common in most areas of the United States,” he said. 

But before wolves were killed off, they used to kill coyotes. They would scare them into different behavior, the "ecology of fear," he said.

But when coyotes dominate, they prefer rabbits and hares (which of course is whey have become so common in suburban areas.) But in the forest up north and elsewhere they kill snowshoe rabbits, and, indirectly, the lynx.

“Coyotes have a flexible, wide-ranging diet, but they really prefer rabbits and hares, and they may also be killing lynx directly,”  Ripple said.

 
Between the decline of their central food supply and a possible increase in attacks from coyotes, the Canada lynx has been in serious decline for decades and in 2000 was listed as a threatened species. It also faces pressure from loss of habitat, the scientists said, and perhaps climate change as lower snow packs in winter further reduce the areas in which they can find refuge.


Wolves have a similar impact on other species as well. In Yellowstone National Park, for instance, the return of the wolf has also brought back streams and riverbanks that were eaten out by Elk.  But where coyotes take the place of wolves, they have had an enormous impact on ranch animals.

This YouTube video explains it.


 
“In the absence of wolves, coyote densities and distributions generally expanded in theU.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 research is needed to document it, early evidence indicates that a snowshoe hare recovery may be taking place, he said.

 

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