I had hoped, but didn’t expect, to see wolves in Yellowstone. Ever since I was a young lass, they held a certain fascination for me. There is a dangerous grace; a beauty even, about wolves – something fundamentally wild. So on my first trip to the US two years ago, I stumped up the cash for a short detour to Wyoming and the world’s oldest national park.

At first, I mistook it for a coyote. I was tramping near Crystal Creek in the northern part of the park when I spied her trotting across the snow. She was stunning. She was bigger than I’d expected. And she was just a few hundred meters away. It was like a thousand National Geographic episodes come to life. I couldn’t reach my camera. I didn’t want to. I just sat in my ass in the snow and stared, for the longest time, until she wandered out of sight.

I was lucky, not just to be in the right place – but to be there at the right time. As recently as 20 years ago, there were no wolves in the park. Yellowstone’s wolves are a symbol of a massive shift in national park policy precipitated by discoveries in biology and a new school of conservationist thought called rewilding.

“Today, it is difficult for many people to understand why early park managers would have participated in the extermination of wolves,” the National Park Service writes. “But this was an era before people, including many biologists, understood the concepts of ecosystem and the interconnectedness of species.”

Rewilding is based on an assumption that top predators play a disproportionately large role in keeping ecosystems healthy and diverse. It has come out of a field called island biogeography, which is concerned with the relationship among species in isolated patches of habitat (and is a fascinating field in itself: see resources below). Removal of these top-tier predators changes the way other species interact, commonly resulting in a population explosion of the species which would usually be the top predator’s food. This is one form of a trophic cascade which, as the name suggests, often have devastating effects across the whole ecosystem.

But some of the effects are not as clear-cut as you’d expect. In a short film released last month by Sustainable Man, rewilding advocate George Monbiot explains how the wolves have changed the course of rivers in the 3,468 square miles of Yellowstone National Park.

In the absence of wolves, deer populations in the park were out of control. They had overgrazed and the flora was struggling. As soon as the wolves arrived, however, their impact was striking.

“First, they killed some of the deer but that wasn’t the major thing. Much more significantly, they radically changed the behavior of the deer,” Mr Monbiot said. “The deer started avoiding certain parts of the park, and immediately those places started to regenerate.”

The increased trees brought birds, and beavers, which made dams that housed otters, ducks, fish and reptiles. Wolves controlled the coyote population, which let the rabbits and mice recover and that brought weasels, badgers and birds of prey like bald eagles. The regrown vegetation helped the river banks to stabilize and prevented erosion.

“The wolves, small in number, transformed not just the ecosystem of Yellowstone National Park but also its physical geography,” Mr Monbiot said.

It’s not just big, national parks that benefit from rewilding. An astonishing 2007 film shows wild coyotes living in tiny refuges of land, isolated by miles of suburban San Francisco.

Still Wild at Heart filmmaker Melissa Peabody told a forum at the Wild Equity Institute last night that coyotes were so wily and resourceful that they had found homes in these tiny parks – one of them, Bernal Heights, measures only 26 acres and has a tiny stand of trees for shelter. The Bernal Heights coyote had been blood-tested and identified as being from a population north of San Francisco. To get there, it must have navigated the Golden Gate Bridge and 11 miles of suburbia.

Unbelievable, isn’t it? But you’ve seen the cartoons so you know what coyotes can do.

Ms Peabody said the presence of coyotes in cities like Chicago, which has a suburban population estimated between 400 and 2000, had kept other predators in check and reduced the city’s reliance on poison for pests.

It is not just about science, either. Groups like the Nebraska-based Cougar Rewilding Foundation want cougars (aka mountain lions) reintroduced to the Rocky Mountains. Why? Because they’re beautiful.


The National Parks Service examines the lessons learnt from the reintroduction of wolves at Yellowstone.
A long-term study of Chicago’s coyotes.
The Rewilding Institute explains its goals.
George Monbiot’s engaging TED Talk on rewilding.
A beginner’s guide to island biogeography is David Quammen’s excellent book Song of the Dodo. Also check out IslandBiogeography.org