Many years ago my brother and I hiked mile after mile through tangled brush along a small, winding stream. After several hours we reached our destination, a large beaver pond that had held large brook trout. Only this time the pond—which had been the size of a small lake—was dry. We hiked out on the ridgeline and never spoke one word. Five years later I hiked back in and found a field of grass and reeds. The pond was gone, and so were the fish. But why?
After five years of study a team of scientists using GPS to track wolves in the Voyageurs National Park had found that wolves preying on beaver affect water flows in the park.
Voyageur researchers tracked 30 wolves fitted with GPS collars.
What those researchers learned was that when beaver were killed, dams weren’t completed. In one case a beaver pond dried up after wolves had taken the beaver, and five years later the pond was still dry.
As young beaver leave their families to start new homes they are vulnerable to wolves. Many unfinished beaver dams dry out and are replaced with grass and shrubs. Dubbed “ecosystem engineers” beavers create dams that make up much of the wetlands in boreal forests and those wetlands become habitat for a variety of animals.
It was noted in the study, “By affecting where and when beavers engineer ecosystems, wolves alter all of the ecological processes such as water storages, nutrient cycling, and forest succession.”
A study of wolves in Alberta, Canada, revealed that beaver make-up about one-third of a wolf ’s summer diet.
Researchers also learned that wolves prey on fish and blueberries.
An earlier predator-prey study conducted in Yellow Stone National Park found similar results. After wolves had been reintroduced to cull the Elk herd, researchers found that once elk numbers were reduced that more willows were growing along streams, slowing erosion on the those waterways. Elk eat willow.
Wolf predation of beavers doesn’t affect the number of beavers adversely in Voyageur Park, noted the study, but did affect movement of water.
“As a top predator and a critical boreal ecosystem engineer, the relationship between wolves and beavers has a broad impact on the landscape. The Voyageurs Wolf Project has now added another piece to this complicated network of animals, plants, and waterways,” noted the report.
Results of the on-going Voyageurs Wolf Project, which is a collaboration between the University of Minnesota and Voyageurs National Park, with funding assistance from the Minnesota Environment and Natural Resource Trust Fund, were published last week in the Sciences Advances journal.
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