Keystone Species: How Predators Create Abundance and Stability

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Long reviled as beasts of waste and desolation, wolves — along with other keystone predators — actually bring ecological stability to the habitats in which they live.
Long reviled as beasts of waste and desolation, wolves — along with other keystone predators — actually bring ecological stability to the habitats in which they live.
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Bears delay, or even forego, total hibernation when they can scavenge deer, elk and moose carcasses left by wolves. 
Bears delay, or even forego, total hibernation when they can scavenge deer, elk and moose carcasses left by wolves. 
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Cougars in Yellowstone National Park, in the absence of wolves, had expanded their hunting range beyond its natural boundaries. 
Cougars in Yellowstone National Park, in the absence of wolves, had expanded their hunting range beyond its natural boundaries. 
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The reclusive wolverine climbs trees and towering mountain walls with equal agility. 
The reclusive wolverine climbs trees and towering mountain walls with equal agility. 
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Reintroduction of wolves to Yellowstone thinned the excessive population of elk, enabling much-needed regrowth of willow, aspen and cottonwood trees.  
Reintroduction of wolves to Yellowstone thinned the excessive population of elk, enabling much-needed regrowth of willow, aspen and cottonwood trees.  
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Attracted by the regrowth of trees and other woody plants, beavers built dams that created pond and marsh habitats for moose.
Attracted by the regrowth of trees and other woody plants, beavers built dams that created pond and marsh habitats for moose.
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Elephants so profoundly affect their habitat that they’re known as “ecosystem engineers.” 
Elephants so profoundly affect their habitat that they’re known as “ecosystem engineers.” 
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Aspen trees in Yellowstone once again flourish because wolves keep the elk population in check.
Aspen trees in Yellowstone once again flourish because wolves keep the elk population in check.

The day came clouded and wind-tossed, with 5 inches of fresh snow in the valley and a lot more piling up overhead on the peaks. It was early December in Montana in Glacier National Park. Although winter wouldn’t officially start for another two weeks, blizzards and bitterly cold temperatures had long since sent the bears into their dens.

But not every bear.

Very large, very fresh paw prints on the trail in front of me said at least one grizzly wasn’t ready to call it quits for the year.

Sleeping in underground dens keeps bears safe and insulated through the snow-smothered months while they live off reserves of fat. The biggest and most powerful ones — adult male grizzlies — sometimes leave their hidden chambers to roam about during midwinter thaws. Before, few naturalists realized these heavy-bodied bears could stay out through much colder conditions as long as they were able to take in more energy from food than they burned trying to find it. Then wolves returned to the American West.

The Food Web Surrounding Wolves

  • Published on Mar 8, 2021
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