Eager: The Surprising, Secret Life of Beavers and Why they Matter

eager Coverreview by Jack Kittredge

Beavers, the world’s second largest rodent (after South America’s capybara) used to be everywhere. They come in two varieties, the North American one (Castor canadensis) of whom there were an estimated 90 million inhabiting every stream and creek in the temperate part of the continent before Columbus, and a Eurasian one (Castor fiber) which was equally widespread in the old world.

The hallmark behavior of beavers is to build dams to slow the flow of streams and raise the level of water, causing flooding. The resultant ponds enable the rodents to reach their favorite foods – trees such as willow, cottonwood and aspen. These, once toppled by the animal’s amazing gnawing capacity (using self-sharpening teeth) and floated to the center of the pond, can be piled and stored for winter fodder largely unreachable by predators on shore.

Native Americans were divided on the acceptability of hunting beaver. Plains tribes like the Blackfeet had strict prohibitions against killing beavers in, as anthropologist R. Grace Morgan put it, “response to the limited availability of surface water and a recognition of the beaver’s role in maintaining these resources”. Forest tribes like the Cree, Goldfarb asserts, had no such restrictions. There, flooding was an obstacle to hunting, not a blessing.

When Europeans arrived in this continent, however, they were not constrained. Beaver pelts were in much demand and the populations were heavily reduced by European trappers for their fur and also for castoreum — an exudate from their castor sacs with uses in perfume and food — and came close to extinction almost 200 years ago. In 1843 John Audubon journeyed 2200 miles along the Missouri River searching for mammals to paint. He never saw a single beaver.

Many settlers also saw little use for beavers, blaming them for flooding cropland and blocking water flows used for animals. Others, however, recognized the long term benefit they brought to agricultural production.

This benefit, as Goldfarb puts it, was that: “beaver ponds slow flows, trap sediment, and gradually fill with silt and pioneering plants, whereupon their creators move upstream to begin the cycle again. Left behind are open, grass-filled meadows – their surfaces flat, treeless, and flan-like underfoot, bermed with the overgrown contours of long-ago dams.” These beaver meadows sometimes covered hundreds of acres and were rich feeding grounds for deer and other animals. Settlers moving to these locales found the soil, rich with “leaves, bark, rotten wood and other manure”, ideal for agriculture, producing as much as four tons of hay to the acre.

Environmentalists of today recognize another value that beavers bring to land. When water rushes through a streambed it scours out silt and soil, carrying them downstream and eroding the landscape. Also, the water itself is rapidly carried away, ultimately to return to the ocean. By slowing flows, beavers give that water time to settle, drop much of the sediment it is carrying, and even percolate through the soil and remain as groundwater. Much of the reality of arid areas is not that they don’t get any precipitation, just that the water does not stay for long.

Reintroductions of beavers into the wild in arid regions like Nevada and Utah have been very successful in exactly that work — reviving landscapes parched for moisture. In other areas, particularly where humans see marshes and ponded water as destructive to their purposes, they are still very controversial.

Eager is the story of those reintroductions. Sharp-eyed wildlife managers, and often enough their bosses in municipal and state government, have begun to use these hard-working mammals to reduce erosion and restore groundwater, especially in the West. Goldfarb visits dozens of sites around America where beavers are being reintroduced, travels with the committed beaver enthusiasts (sometimes on official work, sometimes on clandestine missions) and helps the rodents find streams, mates, and a chance to do their special work undisturbed.

The author is an entertaining writer and brings the beavers’ proponents, as well as plenty of the ranchers, farmers, and engineers still adamantly opposed to the reintroductions, to life. He sees both points of view regarding his subjects, and waxes particularly enthusiastic about the many efforts to construct devices that enable these rodents to earn their living without flooding roads or drowning fields. Such devices are many, some rough and ready, others carefully fabricated, but essentially they all enable the slowed water to flow once it reaches a certain height. They let the beaver dam impound water and create ponds, but prevent the beavers from blocking a final elevated outlet by using pipes, fencing, grids, and other man-made creations to frustrate them. These devices, and the compromises they enable, are of course not perfect and require regular maintenance and repair, (on which trips Goldfarb happily catches a ride). But they seem to be doing an important job of mediating between the natural and the anthropocentric worlds.

If you like wildlife, would like to engineer a device to enable beavers to cooperate on your land, or just like stories about passionate people taking a stand for what they think is right, you will enjoy Eager.