"Nature's Engineers"
Beavers (Castor canadensis) can gnaw through a 6-inch (15-centimeter) tree in 15 minutes. A single busy beaver chews down hundreds of trees per year. The trees are used to build lodges and large dams that provide their aquatic habitat. Dams can range from 2 to 10 feet (2 to 3 meters) in height and stretch more than 100 feet (30 meters) in length.
Streams and lakes are favorite stomping grounds, but water sources like farm ponds, wetlands, and other areas will do, as well.
Picone notes that beavers are among Connecticutt's most problematic animals for humans, likely ranking just behind deer in terms of economic damage. Their tree-felling and large-scale flooding can damage timber and agricultural crops and wash out property and often roads.
"Where humans and beavers can coexist, we encourage it," Picone said. "Beavers create great habitat for other animals. Wood duck, great blue heron, river otter—they all benefit from that habitat that beavers create."
Other benefits include, ironically, flood control through water management, and water storage and purification.
"Everybody sees the negative impact, Mueller-Schwarze said. "People remember the beaver that took down the cherry trees in the [Washington, D.C.] Tidal Basin. The positive effects are harder to see."
The positives are real, but unfortunately for the beavers, so are the negatives.
"The benefits have to be balanced with the damage [beavers cause] to people's property and with flooded roads," Picone said. "It's a tough balance."
Trapping: Cruelty or Conservation?
Solutions—such as fencing off trees and installing free-flow water devices through dams—can mitigate beaver problems and leave habitat intact. But reviews on their effectiveness are mixed.
Another beaver control method is contested for both its results and its application—trapping. As trapping for valuable pelts has declined, nuisance-control trapping has grown. States like Connecticut and New York facilitate the process.
"Here in New York they have a management plan where they want to keep the population limited to 20 or 30 percent of the available [habitat] sites along streams, with food and water, in areas where they won't do damage to human works," Mueller-Schwarze said. "The idea is that when the colony produces young beaver [who go off in search of their own turf], they will have a suitable place to go—the remaining 70 percent of those sites."
The policy is managed by lethal trapping, though Mueller-Schwarze would prefer to see the animals relocated when possible.
The Washington, D.C.-based Humane Society of the United States (HSUS) opposes lethal trapping.
"We oppose the kinds of traps that drown these animals," said biologist John Hadidian, director of HSUS's Urban Wildlife Program. "We oppose the traps that crush them, those that are supposed to break their backs but often don't."
Hadidian argues for better management methods that can help mitigate beaver problems and leave the animals in place with naturally determined numbers.
"We understand that there are people who have trouble dealing with these conflicts, but we don't agree that they need to be lethally disposed of in order to solve these problems," he said. "Even if it was necessary, there are humane ways to do it. These devices that trap them and drown them are inhumane."
NTA's Scott Hartman says that modern traps are a humane way of controlling beaver populations. He notes that in states like Massachusetts, where trapping has been banned, debate rages over the costs and impact, for good or ill, of the policy of not trapping beavers.
"The animal rights folks have made it an emotional issue," he said. "They're dealing mainly with quality of death and we deal with quality of life. You can't stockpile wildlife, you can only have so many animals living in an area. When populations become too high you get disease and you have more animal-human conflict," he said.
For some that conflict's bottom line is defined by dollars and sense.
"It depends how tolerant the local people are," Mueller-Schwarze said of reactions he's seen to beavers in the neighborhood. "Some are excited and some are annoyed, and the same person may tip from one to the other if the damage gets worse. There was a Cornell University study some years ago that determined that the magic number was 400 [U.S.] dollars. People didn't mind up to that point, but after more damage was caused, they often wanted someone to 'take care' of the beavers," he said.
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