Book Summary: Eager: The Surprising, Secret Life of Beavers and Why They Matter

My Personal Summary

This book is about the secret life of beavers and why they matter.

Beavers create dams using rocks, mud and trees, which create ponds and wetland areas.

These areas support a massive amount of biodiversity, which is why beavers are known as keystone species. Without beavers, many organisms including frogs, swans, fish, otters, and many types of plants would be unable to thrive in many parts of the U.S.

Wetland areas are important because they’re able to filter fertilizers and other pollutants out of running water before they can reach the ocean and they prevent streams from causing too much erosion and ruining landscapes.

Despite beavers being nearly hunted to extinction in the 1800’s, environmentalists are finally realizing just how important they are and their numbers have slowly been increasing in recent years.

Book Notes

  • From the 1820’s to 1840’s, beaver trappers ransacked nearly every pond and stream between Colorado and California. They sent most the pelts on the Missouri River where they made their way to St. Louis, which then were shipped to the East Coast or Europe to make fashionable hats using the beaver pelts.
  • Beavers build dams using wood, rocks, and other material, which backs up rivers and streams, creating wetland areas that are crucial for biodiversity to thrive.
  • Wetlands only make up 2% of total land area in the intermountain West but they support 80% of biodiversity by providing homes for a myriad of birds, frogs, fish, swans, otters, and many other species.
  • The weight of wetlands also presses water deep into the ground, recharging aquifers for use by downstream farms and ranches. Wildfires also get extinguished naturally when they encounter wetland areas. Wetlands also capture and store spring rain and snowmelt, releasing water in delayed pulses that sustain crops through the dry summer.
  • “The disappearance of beavers dried up wetlands and meadows, hastened erosion, altered the course of countless streams, and imperiled water-loving fish, fowl, and amphibians – an aquatic Dust Bowl.”
  • The beaver population in the U.S. was about 100,000 in 1900 but today is over 15 million. This sounds like a lot, but it’s estimated that there were over 100 million beavers in the U.S. before Europeans arrived.
  • Beavers are especially crucial to the environment in the western half of the U.S. because it receives so much less rainfall than the east.
  • “Back east you have water no matter what, but we have streams that run dry. And beavers can just make wetlands appear here. They’re kind of magic.” -Mary O’Brien, scientist in Utah
  • Over millions of years, about 30 different genus of beavers have existed. Today, only two exist – the North American beaver and the Eurasian beaver.
  • Beavers are the largest rodent in North America and the second largest rodent in the world, behind South America’s capybara.
  • The main reasons that beavers build dams are for shelter from the elements, safety from predators, and a place to store food.
  • Beavers have several predators including black bears, cougars, coyotes and wolves. By building homes in water, they’re able to steer clear of these predators.
  • Beavers can hold their breath for up to 15 minutes, they have webbed feet for better underwater movement, transparent eyelids that allow them to see underwater, and a second set of fur lined lips that allow them to chew and drag wood without drowning. Despite being clumsy on land, they thrive in the water.
  • To obtain materials for building dams, beavers chew down trees. Beavers also eat the cambium of trees – the layer between the bark and the wood – for nutrition.
  • Interesting: Beavers often eat their own feces to regain any nutrients that weren’t previously absorbed the first time they ate the food.
  • Beavers have two types of hair – stiff guard hairs about two inches long on the outside and wool underfur below it. This fir below the surface is what became fashionable for hats and clothing in the 1820’s-1840’s that drove trappers out west to nearly hunt beavers to extinction.
  • Beavers tails serve a variety of functions – to help them balance on land, as a rudder in the water, and as a place to store fat during long winters. They also slam them on the surface of water to scare and ward off predators.
  • Beavers played a role in many geopolitical events between European arrival and the Civil War because much fighting stemmed from desire over control of lands where beavers abounded.
  • Lewis and Clark frequently journaled about all the beaver dams they encountered on their expedition up the Missouri River and often marveled at how impressive their structures were.
  • Part of the reason that demand for beaver pelts decreased in the mid 1800’s was because cheap Chinese silk became an alternative for making hats and fashion trends happened to change, which probably prevented the beaver from going completely extinct.
  • Ecologists refer to beavers as a keystone species because their ecosystems rely on their behavior so much.
  • Beavers can inadvertently create dams that cause the level of ponds to rise and floods nearby residential or commercial areas. One humane solution to this problem is to install flow devices in ponds – devices that use a fence and pipe to gradually drain a pond to a lower level to prevent flooding.
  • Beavers also frequently clog culverts – the pipes that allow water to pass under roads – which causes roads to food. However, it’s been shown that beaver deceivers (basically fences) placed near the culverts prevent beavers from being able to clog them. This allows beavers to still thrive without needing to be killed.
  • Beaver dams create deep, cold ponds, which offer the perfect environment for juvenile salmon to thrive.
  • Beaver dams also slow down the flow of water through rivers, which decreases erosion that would otherwise occur due to fast moving streams.
  • Studies have also shown that fish typically have no trouble passing through beaver dams when they need to; the fish simply wriggle through tiny holes, swim through side channels, or in some cases even leap over the dams.
  • Interesting: Studies have shown that non-native fish in areas are unable to pass through beaver dams, suggesting that beavers could be a valuable tool for preserving a stream’s indigenous fauna.
  • Beavers naturally create wetland areas, which filter out fertilizers and other pollutants before they’re able to reach the sea and create algal blooms, which are “dead zones” where fish and other aquatic life like clams and mussels are unable to survive.

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