Eager Beaver

Meet Eager. He is a two-and-a-half-year-old beaver. His family has eight members now: his mother, father, two siblings from two years ago, plus the three siblings born last year. Eager is feeling the need to move on before his mother has more kits early this summer. Don’t be critical – Eager has always been ready to help, bringing delicious vegetation to the kits, helping maintain the dam, constructing a second lodge, securing winter stores. It all comes pretty naturally, but he’s learned a lot from his parents. It is early spring and Eager is feeling ready to move out and establish a family of his own. Without much ado, he ventures upstream. He feels comfortable in the water but must travel overland when the stream trickles out. He comes to a road, which is a new experience for him. He has no idea that the pursuit of his ancestors opened traveling routes across the US as trappers sought them for their luxurious fur and castoreum. Beavers were nearly exterminated in the US until legal protection finally came in the early 20th century. After some consideration, Eager ventures onward, waddling his bulky body across as quickly as he can. In the early spring there isn’t much cover, but he smells water over there. Upon reaching the shore, he encounters mound after mound of mud and vegetation. Each scent mound smells strongly of some stranger’s castoreum and urine. He knows this is a “No Trespassing” sign. This pond is taken by another family of beavers and he knows he must move on. It is still cold outside, but his two-layered coat protects him. The underfur keeps him warm and the outer guard hairs protect him from abrasions. His hair is so thick, a postage-stamp sized area has more hair than that on an entire human head. For some people, that may not be surprising. Waddling along in a ditch now, Eager catches scent of another beaver. It’s a girl beaver! They hit it off and continue their wanderings together. They find and follow a small stream. It soon gets deeper. The edges are full of cottonwood, willow and even a few aspen trees. His favorite! The perfect home – but it needs improvement. The two now work tirelessly building a dam to widen their stream. They each pick a tree not too far from their chosen dam site. Eager uses his wide tail to prop himself up on his hind legs, and with front paws against his tree, he begins to gnaw. First biting with head tilted left, then tilting his head to the right, he takes big chunks of bark and wood out of the trunk. His teeth are specially adapted for such work. Each of the four incisors – two on top and two on the bottom – has iron-infused enamel on the outside, covering softer dentin below. This inner layer wears away faster than the enamel, keeping his teeth cutting-edge sharp. Good thing they keep growing, because he has a lot of gnawing to do, which wears them down quickly. In two hours, the work is done and the cottonwood falls right where he wants it – into the stream, where the upper branches are within easy reach. It is hard work and fueling himself is a continuous task. He scrapes and eats the inner bark of a chosen branch and chows down on the buds and leaves at the end. Delicious! His digestive system is built for this food. Not just anyone can digest this stuff. His big caecum is rife with cellulose-digesting bacteria and his intestine is six times longer than his body, so he can digest a third of the cellulose he consumes. To get even more of the nutrients, Eager snacks occasionally on his own feces, digesting every last usable bit until his scat is ultimately just a ball of sawdust. Eager and his mate secure long branches into the bank of their dam site and plaster mud and vegetation in place to make a firm foundation. They continue to bring long wooden sticks and secure them at an angle into the bank and muddy foundation. To this they add smaller sticks and branches woven into the superstructure. More and more sticks, ingeniously woven and secured, are caulked with mud, grasses and leaves. The wider and taller the dam gets, the more their newfound pond fills up, creating the perfect habitat, not only for themselves but for innumerable other pond-loving organisms. Beaver are considered a keystone species: an entire community of organisms depend on the habitat beavers create. Housing is also needed for Eager and Castor, who will be Eager’s lifelong partner. Their first home was a burrow dug into the streambank. That was much easier and faster to construct. They could stick with it; after all, one quarter of all beavers live in bank burrows. But with the water level rising every day, they are setting their sights on either a bank lodge or one surrounded by water. A bank lodge, built partly on land, has an underwater entrance just like a water lodge but is more accessible by predators. Inside both types of lodges is a room above water level where they will sleep, raise young, and maybe someday, tolerate muskrats or other unobtrusive freeloaders. The lodge is plastered on the outside with mud that freezes into a hard, plaster-like barrier, protecting the inhabitants from clawing predators. All this work requires lots of timber. The beaver’s stout body is strong, necessary for dragging heavy branches from land into water. Once in the water, they can still gnaw and carry wood since a second lip closes behind the incisors. Flaps also close off the ears and nose, and clear nictitating membranes protect their eyes underwater. Although Eager can hold his breath for 15 minutes, usually underwater forays last 6-8 minutes or less. Eyes, nose, and ears are conveniently located atop his muscular head so his profile above water is minimal. Through the years, Eager and Castor raise their own kits, keep the dam mended, and host innumerable other species in their pond. Consequently, groundwater is recharged, trout and salmon populations flourish, and sediment is reduced for downstream organisms. With luck, Eager and Castor may live up to 25 years in the wild. We wish them well as they are good stewards of their corner of the world. --Nancy Condon Author’s notes: I invite you to An Evening with Beavers on Upper Spectacle Pond on August 14th. See description for details. Recommended reading and primary source: Eager: The Surprising, Secret Life of Beavers and Why They Matter by Ben Goldfarb, 2018.