Nature Notes: Busy Beavers
People often use the phrase "busy as a beaver" to describe a hardworking individual who is always focused on completing tasks. It's an apt name, for beavers are said to be second to only humans in the way they modify their habitats. In their native ranges, beavers are a keystone species, meaning they play a vital role in the ecosystem around them. These ecosystem engineers modify their habitat through roles as a timber harvesting and dam building, changing the way water flows on the landscape. By damming rivers, they're creating aquatic habitats for a wide variety of plants and animals, but they're also slowing water on the landscape. Slowing water means less flooding and erosion, more water filtration, and increased water storage in ground water, which can even help reduce the risk of wildfires!
In fact, beavers are such an important species, that in 1948, after multiple failed attempts to reintroduce beavers to rugged Idaho landscapes via trucks, Operation Beaver Drop began. The Idaho Fish & Game Service air-dropped 76 beavers using surplus World War 2 parachutes. They were dropped in wooden crates, designed to open on landing, and 75 of the beavers survived and went on to engineer the landscape, slowing the water on the steep terrain. And guess what. In 2018, NASA took aerial surveys of the area to examine wildfire damage. The areas that had reintroduced beavers burned significantly less than all the surrounding areas. (You can hear the whole story in the Nature Storytime featuring When Beavers Flew.)
Built for the Role - Biology of Beaver
Beavers were built to play the part. They are equipped with oodles of adaptations that help them dominate the role of timber harvester, architect, and engineer in aquatic, often cold, habitats. So where do we begin?
Beavers are the largest rodent in North America. While most adults weigh-in at about 45 pounds, beavers can weigh over 70 pounds! They have two layers of fur – a dense undercoat to provide insulation and warmth, and a topcoat of waterproof guard hairs - which create a truly luxurious combination. [So luxurious, that beavers were nearly trapped to extinction to meet
fashion demands by the mid 19th century. Populations plummeted from an estimated 60-400 million to 100,000 according to the Animal Welfare Institute.] They have a castor gland which produces the waterproofing oil that is applied to their fur by a specialized split nail on their hind paw, which acts as a comb.
Their back legs are much longer than their front, ending in huge webbed feet that aid in swimming. Their rear-heavy bodies allow them to easily sit upright, balancing on their back feet while working with their dexterous front paws to grab sticks and work with mud to build their creations. Their wide, paddle-like tail acts as a kickstand on land to help them balance, but also serves as a rudder while swimming, an alarm signal creating a loud slapping sound on the water when threatened, and a place of fat storage, to help survive winter food shortages.
Besides waterproof fur and webbed back feet, beavers are drowning in features that aid them in a semi-aquatic lifestyle. They have large lungs and are capable of staying submerged for up to 15 minutes. What's the worst part of swimming? Water forcefully shooting up your nose when you jump in or water refusing to leave your ear long after you've stopped swimming. But not for a beaver. They have self-closing nostril and ear holes to avoid this problem! Not to mention, they have a clear 3rd eyelid called a nictitating membrane that acts as built-in swim goggles. Are you jealous yet? I've saved the best for last: beavers have two sets of lips - one that closes in front of their big beaver teeth and a second set that closes behind. That means they can open their outer lips and carry a stick underwater, sealing their second set of lips to ensure they don't swallow water as they swim. 🤯
Speaking of their teeth... like all rodents, their teeth never stop growing. Chewing on wood grinds them down and keeps them at an appropriate length. And boy can they chew! The orange color on the front of their teeth is from the iron built into their tooth enamel, making them incredible strong. The backs lack this coating and grind down faster, creating self-sharpening teeth that can chew through a 6" diameter tree in as little as 8 minutes. It's estimated that one beaver can cut down about 200 trees per year!
Tune in next week for more information on our busy beaver friends. Learn about beavers as timber harvesters and ecological engineers. Find out about their life in the lodge as well!
So get outside this month and see if you can spot any evidence of beavers getting ready for winter!
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