Beavers – Ecosystem Engineers
Beavers are important architects in our watershed and provide essential ecosystem services. They are important for meadows, streams, and rivers. Why?
Beavers are semiaquatic and possess many physical features and characteristics that are complementary to this lifestyle. Their webbed hind feet and flat, broad, paddle-like tail allow them to navigate through rivers and streams with ease. And like many other semiaquatic animals, the beaver has a nictitating membrane (a translucent or transparent third eyelid) that protects their eyes and allows them to see when submerged. When they are under water, valves cover their ears and nostrils. Beavers are also able to close their lips behind their front teeth, allowing them to continue to gnaw on wood even when underwater.
A thick layer of fat just under its skin helps keep the beaver warm and (much like the wetsuits used by humans) insulates its body heat when swimming in cold water. The beaver’s fur also consists of a double coat, with long, coarse outer hairs and short, fine inner hairs. Scent glands located near the genitals of both male and female beavers release an oily substance called castoreum, which they use to waterproof their fur.
Beavers possess four continuously growing incisors that are coated in thick, orange-colored enamel. This enamel on these incisors is thicker on the front than the back, which allows for a “self-sharpening wear pattern that maintains their chisel-like edge” (Living With Beavers).
Beavers use these sharp incisors (and their strong jaw muscles) to fell small and medium sized trees, which they use (in addition to sticks, twigs, rocks, and mud) to build their homes (or “lodges”) and dams. Beaver lodges may either be located in the middle of a body of water (usually a pond) and surrounded by water or adjacent to a river back. Frequently, beavers will construct a dam across a stream or river and then build their home in the pond that forms as a result of the dam.
Beavers build dams with the intention of creating a deep underwater refuge safe from potential predators. Dams can often result in the flooding of surrounding forest areas, which gives the beavers safe access to the leaves, buds, and inner bark of growing trees on which the beavers rely for food. In addition to providing a safe place for the beavers to call home, beaver ponds also provide resources and habitats for waterfowl, fish, and other aquatic and semiaquatic animals.
When beavers settle into a landscape and build their dams, they are also creating complex, nutrient-rich ecosystems that provide food and shelter for a wide variety of animals.
Deer and elk will graze in the areas surrounding beaver ponds in search of the shrubby plants that grow in place of the larger trees the beavers have cut down. Weasels, raccoons, and herons hunt along the marshy edges of ponds for one of their favorite food sources – frogs. A wide variety of sensitive species (such as red-legged frogs, yellow-legged frogs, Cascades frogs, western pond turtles, and sage grouse) all benefit from the habitats and ecosystems that are created by beaver ponds and wetlands.
Migratory water birds utilize beaver ponds as nesting areas and resting stops along the route of their migration. Ducks and geese will often nest atop beaver lodges for warmth and protection, especially when the lodge is located in the middle of a pond. In mountain meadows, some birds (like the willow flycatcher) use the shrubby re-growth of chewed willow stumps as an ideal nesting habitat (complete with shelter and food sources). The trees that are unable to survive the rising water levels that result from beaver dams attract are fed upon by insects. These insect infestations attract woodpeckers, which build nesting cavities that (after the woodpecker has left) can provide homes and shelter for a wide range of other wildlife species.
In coastal rivers and streams, juvenile salmon and trout rely on beaver ponds and bank burrows for protection from high water flows and predators and to find food while growing big enough and strong enough to venture out to sea. Endangered Chinook salmon, like the ones in the Yuba River, prefer to lay their eggs in slow, freshwater streams, a now rare find that beaver dams and ponds can provide. When beavers are killed or their dams removed, an entire habitat (and all the plants and animals that call it home) can suffer.
In addition to the resources that beaver dams provide for other wildlife that share their habitat, the dams also help reduce soil erosion and flooding and filter sediment (especially that which is left over and results from wildfires). But even with all the environmental and ecological resources this keystone species provides, beavers are still considered by some to be pests. As a result, whole beaver populations have been removed from areas that once benefited from their presence. In many cases, this removal has had (and will continue to have) an adverse effect on a given ecosystem’s health and integrity.
With the continuing changes in climate and heightened severity of weather events, meadows have been made increasingly vulnerable to drought. One way to manage drought conditions and restore the health and viability of meadow habitats is through the improvement of water flow in these areas. This could be achieved through the reintroduction of beaver populations to meadows and streams. Reintroducing beavers could alter the habitat just enough to allow the mountain meadows to hold on to water supplies for longer periods of time. This would help to diminish runoff and flooding events and would provide more dependable and longer lasting water resources for the plants and animals that call these meadows ‘home’.
Over the past few decades, researchers have continued to study the impact beavers have on California’s natural landscape and have determined that these large rodents (the largest in North America, in fact) play a crucial role in ecological restoration. But beaver legislation and policy, which focuses on depredation permits and dam removal, hasn’t been significantly amended since 1981 and overlooks the environmental benefits that beavers provide.
With all the environmental and ecological benefits that beavers, and beaver dams provide, it may be time to update this policy and start considering beavers as a potential partner in meadow restoration.
To read more about SYRCL’s Meadow Restoration projects, click here.
Two new beaver dams constructed at SYRCL’s Hallwood Side Channel and Floodplain Restoration Project site