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Don't damn beavers, study says
The tree-gnawing rodents are environmental saviours that create ponds which support frogs and toads essential to the ecosystem, Alberta researchers discover

Bill Mah, CanWest News Service
Published: Thursday, January 11, 2007

EDMONTON -- Reviled as a pest in some quarters for gnawing down trees, the beaver may actually be something of an environmental saviour, helping reverse falling frog and toad populations, a University of Alberta study suggests.

Scientists surveying the calls of male frogs and toads wooing female amphibians counted 5,062 boreal chorus frogs, wood frogs and western toads at 54 beaver ponds over a two-year period in the boreal forests of west-central Alberta, between Drayton Valley and Nordegg.

In contrast, no frogs or toads were found on streams undammed by beavers over 2001 and 2002, says the study published in this month's issue of Biological Conservation.

Using bucket-traps, researchers also caught nearly six times the number of wood frogs, 29 times more western toads and 24 times more boreal chorus frogs than on nearby free-flowing streams.

"That there was such a large effect, that was surprising for sure,'' said lead researcher Cam Stevens.

Beaver ponds with their still waters create good habitat for frog and toad breeding, Stevens said.

Small ponds and wetlands are vanishing because of warmer, drier weather, he said.

"But the beaver is able to create these ponds that would otherwise not be available.''

The study calls the beaver a "surrogate species'' that can naturally assist other co-occurring species such as frogs.

"The idea is to develop a monitoring and conservation plan around beaver which would be an easier task and a more cost-effective way of protecting the amphibian population.''

Stevens said the findings suggest developers, foresters and energy companies make room for beaver dams in their environmental plans -- which often require addressing threats to frogs and toads.

"By promoting beaver habitat, they're essentially contributing to the conservation of amphibians,'' said Stevens, who named his German shepherd dog, Rana, after a group of frogs.

Conserving frog and toad species has taken on urgency since research starting in the 1980s shows many species are declining worldwide.

Besides being important parts of the ecosystem, Stevens suggests another reason for helping amphibians survive.

"I just want my kids to be able to see frogs and toads like I did when I was a kid growing up in the North.''

Stevens admits promoting more beaver dams in order to boost frog and toad numbers will be a challenge because of the damage often caused by beavers.

The Alberta Sustainable Resource Development website describes beavers as a costly problem for the government.

"More money is spent on preventing and paying compensation for flood damage caused by beavers than all other wildlife,'' the website says.

"Thus, trappers provide a service by removing surplus animals that may otherwise cause problems.''

Stevens says land managers will have to be creative. He suggests preventing beavers from damming sensitive areas, say a culvert near a road, but enhancing beaver habitat nearby.
© The Vancouver Sun 2007