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Doug Smith, Yellowstone Beavers and Salmon

Although most people hear the name Doug Smith and associate him with the Yellowstone Wolf Biologist, he also wears another hat.  Smith did beaver projects beginning as far back as 1984 at Voyageur’s National Park, then went on to study beavers in five national parks.  He completed several aerial surveys looking for beavers in Yellowstone National Park, the first in 1996 and the last one documented in Yellowstone Science was in 2007.

I won’t go into the whole report here, but essentially beaver colonies have increased over the last 20 years in the Park due to several things:

  1. Willow regeneration, probably due to reduced browsing, and most importantly…
  2. A rapid re-occupation of beavers along the northern range, especially along Slough Creek, because Dan Tyers of Gallatin National Forest released 129 beavers in drainages north of the Park between 1986 to 1999.

Tyers did a survey of the Absaroka-Beartooth Wilderness in 1985 and found no evidence of active beaver populations.  He talked with old-timers, sheep herders, outfitters, and MTFWP employees about the area’s history.  What they told him was that beavers were abundant until around the 1940’s and 1950’s. There was general agreement that the decline was due to persistent over-trapping, some disease, and a decline of willow stand (beavers in the GYE mostly use willow) due to over-browsing by moose and elk.

In 1996 there were 49 known beaver colonies in the Park.  In 2007 the number had stabilized to around 127.  These sites overlap fairly consistently with willow stands and slower water–mostly in the southeast, the southwest, and the northwest of the Park. The re-introduced beavers just north of the Park jump-started this healthy increase.

In the Sunlight Basin area, there used to be beavers, but they have been consistently trapped and removed.  Even recently as noted in my previous post, a beaver colony began making some headway down at Russell Creek on mostly forest land, but once on private land, the homeowners trapped and killed them.  A lot has been said about the reduced moose population in the basin over the last thirty years.  If we had beavers here, moose habitat would greatly expand.

So why all this animosity towards these large rodents?  Beavers, as we all know, gnaw down large trees.  They also can plug up culverts and irrigation ditches and flood fields. Yet if you want to have a healthy ecosystem, you need beavers. They are considered a keystone species, building habitat for birds and mammals literally from the ground up. They reduce stream incision, slowing water and creating a soil base for plant life that wildlife feeds on.  And if you’re willing to work with beavers, there are many ways to prevent culvert damage.

In a new twist, beaver dams once thought to be a deterrent to salmon swimming upstream and so were removed, are now thought to be the only thing that can save the West Coast salmon population.  Not only can the salmon easily cross beaver dams, but since beavers slow water, they also raise the water table.  Stream restoration in California that included beaver dams more than doubled salmon production.

“Beavers are the single most important factor in determining whether Coho salmon persist in California,” MKWC executive director Will Harling says.

What’s more, Pollock’s work shows that by slowing a river’s flow and allowing water to soak into the ground, beaver dams can raise the water table under the land. “So they don’t just help fishermen,” he says, “but can help ranchers and farmers save on water pumping and irrigation costs.”

Garreth Plank, a cattle rancher on the Scott River, has always welcomed the animals to his land. As a result, he has found that the beavers save the ranch significant amounts of money each year. “One of our largest expenses is electricity for pumping water,” Plank says. “With beavers on the land, the water tables are higher, and we’ve had a 10 percent to 15 percent reduction in pumping costs.”

“Due to their benefits, we started planting more trees, and instead of calling it riparian and shade plantings, we call it ‘beaver food.’ “

We need new ways of thinking about this little engineer.  Smith says that in the Greater Yellowstone Ecosystem, drought may be advantageous to the rodent.  Drought slows down spring melts and allows more areas where the beavers will build.  And in a warming climate, the Greater Yellowstone may need beavers to increase water conservation, and habitat for wildlife.