Ecology

Fish mismatch makes bears eat elk

    In bringing lake trout to Yellowstone National Park humans may have inadvertently triggered a cascade of changes with consequences for migratory elk.

    A team led by Arthur Middleton, then at the University of Wyoming in Laramie, looked at the long-distance effects of introducing lake trout to the park in the western United States. The lake trout have caused a marked decline in native trout and, unlike the natives, the interlopers spawn on lake bottoms — out of reach of grizzly bears.

    Earlier research suggested that, when fish are in short supply, grizzlies prey on elk calves. The authors used a demographic model to calculate that this dietary shift has cut the growth of elk populations by as much as 11% — even in groups that overwinter well outside the park. The decline of these elk is often blamed, perhaps erroneously, on the reintroduction of wolves.

    Credit: BARRETT HEDGES/GETTY

    Proc. R. Soc. B http://dx.doi.org/10.1098/rspb.2013.0870 (2013)

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    Fish mismatch makes bears eat elk. Nature 497, 412 (2013). https://doi.org/10.1038/497412a

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