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Just a few hundred years ago, beaver dams submerged up to 234,000 square miles of North America. (For reference, Lake Michigan is 22,394 square miles.) This represents 150 million ponds averaging one acre each. European settlers wasted no time before embarking upon extermination; beaver pelts partly financed the Mayflower voyage. Henry Hudson traded with the Mohawk for pelts even earlier. Steel traps were in service by the early 1700’s.
Fortunes could be made from beaver fur because the fine, barbed hairs made the best hat felt available. A stamp-sized piece of beaver skin might host 126,000 hairs, a dense casing that kept beavers dry and warm enough as they swam through icy water.
These facts and many more are assembled in Ben Goldfarb’s important and entertaining book, Eager the Surprising, Secret Life of Beavers and Why They Matter. (The title is under-punctuated.) Beavers matter because they are a keystone species, one that can “support an entire biological community.” Goldfarb paints a portrait of North America before European settlement, in which the very land forms are unfamiliar to us because beavers once engineered wetlands from sea to shining sea. The simple streams we are accustomed to have replaced complex and ever-changing webs and chains of dams, ponds, and meadows, that held back water, recharged aquifers, and provided habitat for boundless life.
Here are some uses by wildlife: ducks nest in grasses at pond fringes and songbirds in coppiced willows, swans nest atop lodges, other birds nest in snags created by drowned trees. Turtles and lizards are more abundant near beaver ponds, fish communities are more diverse near beaver dams, minks and raccoons hunt crawdads and snakes in beaver complexes, northern leopard frogs breed in beaver ponds, aquatic insects shelter in the nooks and crannies of dams and lodges, and moose eat the wetland plants that colonize beaver ponds. Plant species are increased by one third in beaver zones. Whew! Compare that to depauperate streams in arid country that dry out every year or surging rivers that erode their beds down to rock, both because there are no beaver dams upstream to regulate flow.
This book tours sites across the country and introduces a host of people instrumental in the re-beavering of North America. It tells amazing tales of reclamation and chronicles of conflict. Land management policy tends to endorse rigid control, even when excellent results can be achieved by working with nature. Granted, beavers take some managing. Our culture has developed and settled thickly in the lowlands and river valleys that attract beavers, and their structures will flood infrastructure if not managed. Enter the beaver deceiver. A variety of devices have been designed that will penetrate a beaver dam and lower the water enough to protect roads, railroad tracks and the like without provoking beavers to initiate repairs. They can prevent beavers from blocking culverts. The key seems to be extending pipes from the breach back into the pond, where caging can protect the intake. Every site is different, and poorly designed systems often fail, giving the whole approach a bad repute, but many managers have found the process highly cost effective.
Beavers have also caused controversy among fish managers. Sometimes they do block passage, although pre-settlement fish obviously thrived among beavers. They evolved together. Adult salmon can leap over dams, and side channels will often allow youngsters to pass downstream. A beaver deceiver can open a passage to fish when required. On the plus side, because beaver dams slow down spring floods, allowing snowmelt to recharge the water table, they render more streams useable to fish. Lands Council researchers “estimated that beaver ponds held five to ten times more gallons beneath the [soil] surface than they did above it.” That water is available to keep streams flowing long after the melt season.
Reintroduction of beavers is no slam dunk. One of the most successful operations relocates problem beavers to Washington State’s Methow Valley, currently at 15 – 20 % of its historic beaver population. Cue the rodent love motel.
Beavers are more likely to establish where they are placed if they arrive in pairs, but they have their own ideas about who is a suitable mate. The Methow group keeps an aquatic complex where pairs can bond – or not – in man-made lodges. It is helpful to release them in fall rather than spring, so they will get busy building a lodge rather than lighting out to explore the territory. Sometimes people will even prime the release sites with human-made starter lodges and dam analogues so the beavers have immediate protection from cougars and other predators.
This book has so much more to offer. Hunting and nuisance removal take huge numbers of beavers, even in zones where people are attempting to increase populations. Beavers are a vital if underappreciated part of the wolf/elk/habitat link; this relationship is discussed with reference to Yellowstone. I haven’t even mentioned the analogous process of restoring beavers in Europe with their closely related species. And, the fun-fact department will not disappoint – giant Pleistocene beavers, etc. I hope that this book will circulate widely, provoke a lively discussion, and result in more tolerance and sympathy for the most industrious rodent.
Credit goes to Mr. P for technical services on this diary. Thanks also to OceanDiver, our gracious coach, who guided us through the process.
Links:
High Country News — more from Ben Goldfarb about beavers.
Science News — reviews the book.
http://bengoldfarb.com/
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