Trophic Cascades from Wolves to Grizzly Bears in Yellowstone?

Commentary by George Dovel

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In Outdoorsman No. 51, the article on pages 8-9 Titled, “Top Wolf Scientist Charges Wolf Researchers Have Become Advocates Rather Than Scientists,” tells how Dr. L. David Mech charged that when wolf advocates began to claim the wolves’ presence was vital to restore healthy native ecosystems, a large number of university researchers invaded Yellowstone Park with the intention of proving trophic cascades caused by wolves.

Then Mech rebutted their claims with facts. He pointed out that the addition of 27 days of growing season in Yellowstone in recent years undoubtedly created healthier and taller willows and aspens and said there was no scientific evidence that wolves were responsible for creating more food for other predators.
He cited a study of 19 chapters of reviews concerning the ecological role of large carnivores, and said a research team concluded that scientists likely will never be able to predict cascading impacts on biodiversity other than prey. After a review by other wolf scientists, it was then accepted for publication in Biological Conservation on March 12, 2012.

But despite Mech’s pointed claims being published a year ago, a new study by William J. Ripple et al claims that wolves reducing the number of elk browsing on serviceberry provided more food for grizzly bears.

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The Ripple study said it measured 778 bear scats in 2007-2009 and determined from those measurements that the bear stools contained more fruit than were found in older studies before wolves were introduced.
The study also determined that the serviceberry bushes grow taller and have less browsing than were found in previous years. That, of course, correlated with the 27-day annual increase in the Yellowstone Park growing season provided by Mech.

The study published by the British Journal of Animal Ecology on July 29, 2013, included a series of unproven hypotheses that: elk and grizzly bears competed for berry-producing shrubs; after wolves were introduced there would be a decrease in elk and an increase in berry-producing shrubs; and the percent of fruit in the grizzly bear diet would be greater after wolves were introduced.

In reality, the killing or alleged relocation of elk by wolves resulted in far fewer elk available as prey for the grizzly bears when they emerged from hibernation and desperately needed the protein provided by elk prey until green-up occurred.

Such thinly veiled attempts to try to promote the trophic cascade myth illustrate how far science has been prostituted by the current crop of students and professors who lack the wisdom and integrity to be scientists.
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Thank you,
George Dovel