Tag Archives: How Wolves Change Rivers

Two Stories about Wolves that Say a Lot about Us

We never seem to let up on wolves. They’ve been a wet nurse for Romulus and Remus, a sexual predator in Little Red Riding hood, but more often just cattle-rustling thieves. We’re still into mythmaking but now we’re spinning our tales from stuff we pick up from biology and ecology, stuff we find psychologically affirming. Where once we saw demons, now we see critters in need of rescuing. Two wolf stories recently in the news illustrate this point.

DM show shot 2This past February in the depths of one of the harshest winters in 20 odd years, Isabelle, a lone female left her enfeebled wolf pack on Isle Royale in Lake Superior and set off across an ice bridge for the mainland in search of a mate, maybe food. And there she died on the shores of Minnesota leaving behind on the island a pack comprised of six or seven adults, including possibly only one potential breeding-age female plus three pups, all that remains of a peak population of 50 wolves.

Seventeen years earlier, a solitary alpha-male had made the reverse journey from the mainland to the island where he took over a pack, drove another to extinction and eventually came to dominate the gene pool, resulting in debilitating back deformities affecting virtually all his descendents.

There is an operatic symmetry—especially when you consider the death—to these to and fro journeys across the ice, both in search of a mate. These are odysseys undertaken across a forbidding landscape, Canis lupus versions of a polar expedition. The alpha male succinctly delivers a story of male over-reach, genetic domination that comes at a terrible cost, aggression gone too far. Isabelle could be painted as a mate-desperate, getting-on-in-years female or maybe as a plucky girl not willing to settle for the same-old, damaged goods on her home turf.

The other prominent story, somewhat more familiar, has to do with the wolves of Yellowstone Park that has been recently revived with a highly engaging YouTube video “How Wolves Change Rivers” with 3,300,000 views. You really must see this.

Using time-lapse photography, the video paints a picture of a miraculous “terrestrial trophic cascade.” It tells the tale of the reintroduction of wolves into Yellowstone Park in 1990s, which has kept the elk population in check, which has allowed the vegetation to be recover from over grazing, which has corrected the erosion problems on the river banks, which has led to different, more satisfactory river courses.

This is a powerful story about redemption. A creature once thought to be a killing-for-killing’s-sake psychopath is reconstituted as keystone species masterminding the return to health of an entire ecosystem. And because we humans made this happened, we also have been redeemed.

DM snow shot 3But a fall from grace quickly followed. A fulsome article in Nature with the requisite scientific bells and whistles, an editorial in the New York Times, which rarely steps out of the world of people to discuss animals, and a blogger writing for the Ecological Society of America, all debunked the assertion that the reintroduction of wolves to the Park has delivered the benefits claimed for it. Our keystone/alpha species has been cast into ecological irrelevance—or maybe not.

Kristin Marshall, an ecologist with the U.S. National Oceanic and Atmospheric Administration in Seattle Washington told Nature that, “the predator was gone for at least 70 years. Removing it has changed the ecosystem in fundamental ways. Wolves did meaningfully structure the Yellowstone ecosystem a century ago, but that reintroducing them cannot restore the old arrangement.”

Recent research suggests that willow shrubs did not do well whether they were protected from elk grazing or not. Where the plants have done well is attributed to beavers, another keystone species, having raised the water table to counteract the effects of drought. And to the extent that the elk population has declined, the debunkers question whether this can be attributed entirely to wolves. Grizzly bears and hunting have also been thinning out the herds.

Two things are being questioned here: one, the facts on the ground in the case of the impact on particular plant species; and two, the “terrestrial trophic cascade”, that predators have a crucial impact on the behaviour of an ecosystem. This top-down theory replaced an earlier notion of a bottoms-up cascade, that the health of plants determines the entire food chain. And not to be left out, some researchers favour the guys in the middle, grasshoppers, herbivores, and beavers, all of which integrate influences from the top and the bottom.

Despite the holes punched in it, the top-down theory is still viable, at least some people think. As quoted in Nature, “James Estes, an ecologist at the University of California, Santa Cruz, and one of the fathers of the trophic-cascade idea, says that the evidence for cascades mediated by changes in animal behaviour rather than by changes in animal number is ‘thin’, at the moment — and that many of the effects that have been documented are spotty and badly need to be rigorously mapped out. Still, he adds, ‘When all is said and done, and everyone is dead 100 years from now, [the trophic cascade] will be closer to right.’”

So the Yellowstone wolf may not have been relegated to some ecological trash heap, quite. He has been caught up in a turf war among ecologists who have learned to resist the anthropomorphic projections the rest of us happily wallow in every time we watch some spectacular National Geographic or Planet Earth extravaganza, porn for nature lovers.

Animals just used to be there. Now as a result of our actions we are put in the position of saving them, especially clever, team players like wolves, who make other species strong by preying on the weak among them. However, it goes without saying, don’t try this at home.

Ecological Society of America: Wolves Take a Blow to Their Rep, March 11, 2014 http://www.esa.org/esablog/ecology-in-the-news/yellowstone-wolves-take-a-blow-to-their-rep/

Detroit Free Press: Lone Female Wolf Found Dead after Crossing Ice Bridge, February 26, 2014, http://www.freep.com/article/20140226/NEWS06/302260064/Michigan-wolf-population-Isle-Royale

YouTube Video: How Wolves Changes Rivers, by Sustainable Man, February 13, 2014, https://www.youtube.com/watch?v=ysa5OBhXz-Q

New York Times: Is the Wolf a Real American Hero? March 10, 2014 http://www.nytimes.com/2014/03/10/opinion/is-the-wolf-a-real-american-hero.html?_r=0

Nature: Rethinking Predators: Legend of the Wolf, March 7, 2014 http://www.nature.com/news/rethinking-predators-legend-of-the-wolf-1.14841

Photography: Doug McKenzie