In the latest evidence of what Indigenous Peoples have known for thousands of years—namely, that everything is interconnected in ways that we cannot understand—researchers have learned that wolves help bears eat better by catching the elk that eat the berries that are a bear mainstay.
It works like this, says a study published on Monday July 29 in the Journal of Animal Ecology by researchers at the universities of Oregon and Washington State: More wolves mean fewer elk. Fewer elk mean more berries. More berries mean more food for grizzlies, for which the fruit is a major source of nourishment. More grizzly food means, of course, more grizzlies.
“Wild fruit is typically an important part of grizzly bear diet, especially in late summer when they are trying to gain weight as rapidly as possible before winter hibernation,” said OSU professor William Ripple, who teaches in the Department of Forest Ecosystems and Society and was the lead author on the article. “Berries are one part of a diverse food source that aids bear survival and reproduction, and at certain times of the year can be more than half their diet in many places in North America.”
Bonus: Berry-bush flowers that draw pollinators such as butterflies, insects and hummingbirds, Oregon State University said in a statement. The bugs in turn are food for other mammals, and the whole arrangement offers “special benefits to birds,” the statement said.
Among the abundance of nutritious berries in Yellowstone are the serviceberry, chokecherry, buffaloberry, twinberry and huckleberry, OSU said. Highly palatable to bears, their shrubs are favorites of elk, which gobbled most of them up before they had a chance to flower and grow fruit.
“With the return of wolves, the new study found the percentage of fruit in grizzly bear scat in recent years almost doubled during August,” OSU’s statement said.
This is just one way in which having wolves in Yellowstone benefits the entire ecosystem, according to an earlier study by OSU. In December 2011, Ripple published the results of his initial study in the journal Biological Conservation.
“Yellowstone increasingly looks like a different place,” said Ripple in a statement at the time, 15 years after the wolves had been reintroduced. “These are still the early stages of recovery, and some of this may still take decades. But trees and shrubs are starting to come back and beaver numbers are increasing. It’s very encouraging.”
That OSU statement called it an “ecosystem renaissance.”
“The wolves have made a major difference in Yellowstone,” said Robert Beschta, a professor emeritus of forestry at OSU and co-author on the earlier study, in the 2011 statement. The newer study only buttressed those conclusions.
“Studies like this also point to the need for an ecologically effective number of wolves,” Beschta, an OSU professor emeritus who also co-authored the current study. “As we learn more about the cascading effects they have on ecosystems, the issue may be more than having just enough individual wolves so they can survive as a species. In some situations, we may wish to consider the numbers necessary to help control over-browsing, allow tree and shrub recovery, and restore ecosystem health.”
There was a caution, as wildlife expert Arthur Middleton of Yale University told BBC News. In 1988 the northern elk population in the park was as high as 19,000, Middleton said, but last winter it had dwindled to 3,900. Grizzlies also eat elk calves, Middleton said, so an elk decline could just as easily threaten the grizzly as help it.
All parties, including the U.S. Geological Survey, one of the recent study’s sponsors, concurred that Yellowstone is a complex ecosystem and bears much further research.
Below, a National Parks Service video explains the so-called cascade effect of having wolves back.