With its healthy populations of black and grizzly bears, wolves and wolverines, the Yukon stands out as a stronghold for large meat-eating animals. On a global scale, its carnivore guilds are even more of a standout, as the territory is one of the few places in the world where the ranges of five or six large carnivores overlap with one another.

The study of carnivore guilds, a relatively new concept in the field of conservation biology, is giving scientists helpful insights into the importance of animals at the top of the food chain.

"Carnivore guilds are groups of animals that have evolved together in a single habitat type," explains Alan Rabinowitz, the director of Science and Exploration for the U.S.-based Wildlife Conservation Society. One of the oldest conservation organizations in North America, this group takes a science-based approach to protecting wildlife.

Rabinowitz, who recently paid a visit to the Yukon, has been involved in numerous efforts to save individual species of carnivores, from jaguars in the jungles of Belize to tigers in the mountains of northern Myanmar, the country formerly known as Burma.

But after two decades of working on carnivores, he gradually began to realize that trying to protect just one species does not work, particularly when that animal is a carnivore at the top of the food chain.

For example, in Thailand and Myanmar, Rabinowitz and his colleagues controlled poaching, set up protected areas, and increased the numbers of prey, but still the number of tigers did not rebound.

"The animals were not coming back, even though we thought we were taking care of all of the things that we thought were problems. Then I started to realize that they were not coming back because other carnivores that they had been living with had also increased in numbers and were now out competing them."

In this case, the numbers of dholes (Asian wild dogs) and leopards had increased, and these co-competitors seemed to be out-competing the tigers in their own backyards.

The Yellowstone ecosystem has also presented its share of surprises. When wolves were reintroduced to this area, biologists expected to see a drop in the number of coyotes as these animals had skyrocketed in numbers over the last half of a century.

The coyote population did indeed decline by half, but the wolves also had an unexpected impact on cougars, which had been expanding their range back into the Yellowstone area for some time. To everyone's surprise, the wolves soon began to give these cats the boot, chasing them away from their kills and forcing the cougars to beat a hasty retreat to the highlands.

These insights into carnivore guilds have changed some basic ideas about healthy ecosystems. For example, conservation biologists have long stressed the need to protect focal species, animals such as grizzly bears that are at the top of the food chain.

They had assumed that if you protect enough habitat for these top predators, the animals lower down on the chain should also fare well. But carnivore guilds present a more complex view of nature.

"You cannot focus on just on one animal," says Rabinowitz. "We were finding that just by looking at a particular focal species, you might not be getting at the certain ecological processes; so you have to know what is happening with the system."

A global mapping exercise sparked Rabinowitz's interest in this part of the world. Combining Global Information System (GIS) techniques with known ecological data, he and his colleagues looked for places with intact, healthy carnivore guilds.

"Only a few places popped up, and the largest place in the entire world with the largest guilds of the largest carnivores was clearly northwest Canada and Alaska," he says.

"It was a very simple first step but no one had ever done it before. People had talked about ecological hot spots or important areas for large carnivores, but no one had ever looked at the guilds."

The Yukon is one of the few places in the world where guilds of five to six species coexist together. In large parts of the territory, the ranges of wolverines, black bears, brown bears, wolves and coyotes all overlap and in the far north polar bears are also part of the mix.

Carnivore guilds also present a different way of looking at biodiversity. While this part of the world might not have the huge number of species found in tropical areas, it has not lost any of its major species of carnivores, and that fact is a major indicator of the health of ecosystems here.

"You can have a very biologically diverse system in the tropics where a large predator has been eliminated. In some ways, natural large carnivore guilds are even more representative of intact systems than biodiversity."

But, Rabinowitz warns, that lack of diversity also makes places like the Yukon even more vulnerable to outside threats than more complex tropical systems. While Yukon ecosystems might be fit as a fiddle now, losing even one species of predator could quickly change the health of the territory's carnivore guilds.

For more information on the Wildlife Conservation Society, check their website at www.wcs.org.