Wolves and beavers interact throughout North America. Find out how their relationship has a profound impact on wetland habitats.
There’s a large, shallow pond down the road from our cottage called Lake Scugog. It forms out of the Crane River as it flows out into Lake Huron, one of the Great Lakes.
As we move up the river, we see a series of smaller ponds. Each of them is a little higher than the one before. Exploring them means lifting your canoe over one beaver dam after another.
The beavers have engineered this little local ecosystem along with a network of lodges near the water’s edge. This wetland also provides a habitat where plant life like water lilies, cattails and marsh ferns thrive.
BEAVERS HAVE ENGINEERED THIS LITTLE ECOSYSTEM
So do pollinators like hummingbirds and butterflies. Larger animal species include pike, bass, kingfishers, osprey and what people up there tend to call brush wolves. People in other places call them coyotes, and it turns out that they are just as influential as beavers in this habitat.
Beavers are safe from predators in the water, but they can be vulnerable on dry land. The brush wolves snap up younger beavers as part of their omnivorous diet.
The wolves eat mainly small rodents, but also nuts, berries and just about anything else in the forest. Coyotes are intelligent and adaptable creatures.
BOTH HAVE A DISPROPORTIONATE EFFECT ON THEIR ECOSYSTEMS
Ecologists have learned that top carnivores like brush wolves have a disproportionate effect on their environments, just like beavers. Their predatory habits tend to determine the number and distribution of all the other species living in their habitat right down the food chain.
Our local pocket of wetland ecology is a balancing act among the species within it. Even so, these two species, brush wolves and beavers, are the biggest influences on the rest of this ecosystem and most other wetlands.
Brush wolves and the other wolf species have a troublesome reputation with many people. Opinions on the natural role of wolves can get controversial.
OPINIONS ON THE ROLE OF WOLVES CAN GET CONTROVERSIAL
Farmers and ranchers hunted them almost to extinction. Then, unsurprisingly, their fields were overrun with prey species like rodents and deer. Conservation officers started reintroducing wolves to bring things back into balance.
Yellowstone National Park is one of the best-known examples of this reintroduction strategy. Wolves and beavers play an integral role in the success story of the Yellowstone Wolf Project.
The rangers introduced 31 grey wolves from Jasper National Park in Canada into Yellowstone in 1995. Wolves had been eradicated from the park back in the 1930s.
AN EXPLOSION IN YELLOWSTONE’S ELK POPULATION
The hunting led to an explosion in Yellowstone’s elk population. The elk got into the habit of staying in one place all winter and consuming all the willow, aspen and cottonwood saplings.
In turn, the lack of willows adversely affected the beaver population. Beavers live on willow shoots throughout the winter.
Readers might be expecting to learn that reintroducing the wolves cut down the elk population. As it turns out, there are three times as many elk in Yellowstone today as there were in 1968. Yet, there are more willow shoots than ever before.
THE WOLVES GET THE ELK ON THE MOVE
Rather than decimating the elk population, the wolves kept the elk on the move throughout the winter. They didn’t have the chance to stay in one place and munch on the same plants until spring.
The beavers prospered under these conditions and started fanning out to build their dams. They created a new system of ponds, re-balancing the water table.
The new habitats attracted fish and songbirds to the area for the first time in years. Wildlife biologist Doug Smith explained the ripple effect, saying, “It is like kicking a pebble down a mountain slope where conditions were just right that a falling pebble could trigger an avalanche of change.”
THE BALANCE BETWEEN WOLVES AND BEAVERS
The balance between wolves and beavers was also the subject of a study published last week in the journal Science Advances. Professor Tom Gable is the lead author of the study and a member of the Voyageurs Wolf Project at Voyageurs National Park in northern Minnesota.
The study found that wolves and beavers have a surprisingly pervasive effect on the landscape and its inhabitants. As with the Yellowstone elk, it’s not so much that wolves keep beaver populations in check. Their impact has more to do with determining where beavers decide to build their lodges and dams.
Professor Gable explains, “Looking at it over time, you start to see how interconnected wolves are to wetland creation.” The investigators caught 32 wolves over four years and fitted them with tracking collars.
“HOW INTERCONNECTED WOLVES ARE TO WETLAND CREATION”
They tracked the wolves and looked at the remains of animals they had eaten. A lot of them were beavers.
That makes sense because beavers are very plentiful in Voyageurs National Park. In fact, more than 13% of the park’s land area is covered by beaver ponds.
Although the wolves kill many beavers, the overall number of beavers in the park doesn’t diminish. Instead, the beavers who leave their colonies with the idea of starting a new one fall prey to the wolves.
FORESTED AREAS ARE STILL INTACT
This prevents the more enterprising beavers from creating even more ponds. As a result, Voyageurs’ forested areas are still intact instead of transforming into additional wetlands because of beaver dams.
The relationship between wolves and beavers has a profound impact on wilderness habitats. “Given the fact that wolves and beavers co-occur across a substantial portion of the Northern Hemisphere,” Gable says, “this mechanism is likely occurring everywhere wolves are preying on beavers.”
Ecosystems are full of ripple effects like these. Our biosphere is an intricate web of interrelated sub-systems that balance and support one another.
INTRICATE WEB OF INTERRELATED SUB-SYSTEMS
When we disturb those systems, we unwittingly cause our own cross currents that can interfere in ways we can’t begin to anticipate.
Studies like these at Yellowstone and Voyageurs are helping us to understand these processes more clearly. They provide us with stories that give meaning to nature’s complexity.
“There’s been a lot of interest in trying to understand how large carnivores are connected to riparian ecosystems and wetlands,” Gable says. “Our work has presented this simple mechanism that you could explain to a 5-year-old.”
We always have more to learn if we dare to know.
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