The loss of once-plentiful wolves in a part of Canada's west allowed the elk population to mushroom, pushing out beavers and songbirds and showing the importance of top predators, Canadian researchers said. Although scientists have long noted that the loss of even one species can have profound effects, the report is one of the first large-scale studies to show clearly the widespread consequences of losing a predator at the top of the food chain. Mark Hebblewhite of the University of Alberta, and colleagues studied what happened in "a serendipitous natural experiment" when wolves returned to part of the Bow Valley of Banff National Park in Alberta.