Gray wolves are a premier example of how predators can transform ecosystems through trophic cascades. However, whether wolves change ecosystems as drastically as previously suggested has been increasingly questioned. We demonstrate how wolves alter wetland creation and recolonization by killing dispersing beavers. Beavers are ecosystem engineers that generate most wetland creation throughout boreal ecosystems. By studying beaver pond creation and recolonization patterns coupled with wolf predation on beavers, we determined that 84% of newly created and recolonized beaver ponds remained occupied until the fall, whereas 0% of newly created and recolonized ponds remained active after a wolf killed the dispersing beaver that colonized that pond. By affecting where and when beavers engineer ecosystems, wolves alter all of the ecological processes (e.g., water storage, nutrient cycling, and forest succession) that occur due to beaver-created impoundments. Our study demonstrates how predators have an outsized effect on ecosystems when they kill ecosystem engineers.
Bibliographical noteFunding Information:
This work was supported by the Minnesota Environment & Natural Resource Trust Fund, Voyageurs National Park, the National Park Service, the Department of Fisheries, Wildlife, and Conservation Biology at the University of Minnesota, the NSF (grants to J.K.B.; NSF ID no. 1545611 and NSF ID no. 1556676), Van Sloun Foundation, Bell Museum, Thomas H. Shevlin Fellowship, Voyageurs National Park Association, Rainy Lake Conservancy, and numerous small donors and hardworking volunteers.
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