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Issue 73
May 31, 2007


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EnviroZine:  Environmnent Canada's On-line Newsmagazine
You are here: EnviroZine > Issue 73 > Nature

 Nature

The wolf has a story to tell in Banff National Park
This article appears courtesy of Time for Nature,
a Parks Canada series

In Banff National Park, the wolf is an important factor in controlling herbivore numbers. Photo: © Parks Canada, 1998
In Banff National Park, the wolf is an important factor in controlling herbivore numbers. Photo: © Parks Canada, Guindon, A., 1998. -- Click to enlarge.

Maintaining healthy ecosystems in National Parks is a priority for Parks Canada, but it is not a simple task. Ecosystems are complex, so scientists need concrete data to understand an ecosystem and how all of its parts are faring.

Sometimes, that information comes from an unusual source. In Banff National Park of Canada, wolves are providing park managers with important ecological insights into the health of the park ecosystem.

How wolves affect the food chain

Most people know that predators such as wolves affect ecosystems by preying on elk and other herbivores. The wolves help to control these species' populations; however, the wolves' impact on an ecosystem does not end there. Changes in herbivore numbers can in turn affect plant communities and other animals that depend on these plants for food or shelter.

Therefore, whatever affects the wolf should have a cascading effect all the way down the food chain; this is known as a trophic cascade.

Testing a theory

Trophic cascades have been witnessed in other ecosystems, so it seemed likely that they would in occur in national parks. Nevertheless, scientists had little real-world evidence from Canadian parks. Then, quite by chance, the wolves of Banff National Park provided a perfect research opportunity.

In the past, hunting, trapping and other human activities had driven wolves from much of southern Alberta, including the Bow Valley in Banff National Park. Parks Canada worked hard to encourage the wolves to return, and by the mid-1980s, the first wolf pack re-colonized the Bow Valley. Some parts of the valley became high-wolf population areas while some adjacent areas remained low-wolf population areas, primarily due to high levels of human activity.

Large numbers of elk can reduce the growth of the aspen and willow vegetation that other species depend upon. Parks Canada photo provided by Cliff White
Large numbers of elk can reduce the growth of the aspen and willow vegetation that other species depend upon. Parks Canada photo provided by Cliff White. -- Click to enlarge.

Researchers investigated the effects of different levels of wolf activity between the two areas. They looked at wolf predation on adult female elk and their calves, and they also considered effects on the vegetation that elk eat. More elk would likely mean reduced growth of aspen and willow. Finally, the researchers considered how these vegetation changes might affect other species such as beavers (which eat willow) and riparian songbirds, who use willow vegetation as habitat.

As the researchers anticipated, elk were much more numerous in the low-wolf population area than the high-wolf population area. As a result, both willow and aspen showed decreased growth where elk were numerous because more elk fed on the vegetation.

Additionally, as the growth of willow and aspen was reduced in the area, the number of beaver lodges were reduced, and there were also reduced numbers of and fewer species of riparian songbirds.

Wolf and elk numbers also have implications for beavers as part of the trophic cascade documented in Banff National Park. Parks Canada photo provided by Cliff White
Wolf and elk numbers also have implications for beavers as part of the trophic cascade documented in Banff National Park. Parks Canada photo provided by Cliff White. -- Click to enlarge.

This appears to be a text-book case of the trophic cascade concept at work. In fact, researchers had not expected that ecosystems in the low-wolf and high-wolf population areas would be so dramatically different. "We were quite surprised it was such a dramatic effect," said researcher Mark Hebblewhite. Human activity, which kept wolf numbers low in some areas, had clearly made a significant difference.

The research has provided valuable data for park managers who need to balance populations of wolves and elk as part of a healthy park environment.

Fast Facts:

  • Banff National Park has three ecoregions: montane, subalpine, and alpine.
  • Banff National Park is 6641 square kilometers.
  • Wolves have been exterminated in many parts of North America
  • The wolf works hard for its food-a pack kills only about one large mammal for every 10 chased.

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