World's biggest beaver dam discovered in northern Canada

A Canadian ecologist has discovered the world's largest beaver dam in a remote area of northern Alberta, a structure made of animals so large that it is visible from space.

Jean Thie researcher said on Wednesday that used satellite imagery and Google Earth software to locate prey, which is about 850 meters (2,800 feet) long on the south end of Wood Buffalo National Park.

Average beaver dams in Canada are 10 to 100 meters long, and only rarely extended to 500 meters.

First discovered in October 2007, the gigantic dam is in an almost inaccessible area of the park south of the Lake Claire, about 190 kilometers (120 miles) northeast of Fort McMurray.

Dam construction likely began in the mid-1970s, said Thie, who made his discovery by accident while tracking the melting of permafrost in the far north of Canada.

"Several generations of beavers working on it and is still growing," he told AFP in Ottawa.
Mike Keizer, park spokeswoman, said rangers flew over the wetlands heavily forested last year to try to "take a look." They found significant vegetation growing on the same prey, suggesting that it is very old, he said.

"A new dam would have a lot of cool clubs," said Keizer. "This is grass growing on it and is very green."

Part of the dam may have been set up by the felled trees, of course, and beavers "opportunistic fills the gaps."

Thie, said recently identified two smaller dams sprouting on either side of the main dam. In 10 years, the three structures that could merge into one mega-dam measuring just under a mile long, he said.

The region is flat, so the Beavers have had to build a massive structure to contain the flow of water wetlands, Thie said, noting that the dam was visible on satellite images from NASA since the early 1990.

"It's a unique phenomenon," he said. "Beaver Dams are among the few animals structures visible from space."

North American beavers build dams to create deep pools of water to protect against predators, and to float food and construction materials.

A 652-meter structure in Three Forks in the U.S. state of Montana previously held the record for the world's largest dam beaver.

Thie said he also found evidence that the beavers were repopulate habitats of age after having been hunted extensively for fur in past centuries.

"They are invading their former territories dramatically in Canada," he said. "I found large dams across Canada, and the colonies of beavers with a maximum of 100 of them in one square kilometer."