I’m a beaver. You’re a beaver. We’re beavers all.

For greater than 20 million years, beavers have been, nicely, busy. They’ve been felling bushes for that lengthy, and constructing dams and lodges for a minimum of the previous couple of million years, incomes a well-deserved popularity for industriousness and ingenuity. It appeared solely becoming, then, that MIT noticed match to say the beaver as its mascot in 1914. By 1921, The Tech reported that grey beaver hats had grow to be “the distinguishing mark of an Institute man” at school gatherings. The toothy, primarily nocturnal rodent has appeared on each rendition of the MIT class ring—now lovingly referred to as the brass rat—because it was launched in 1929. 

Learn on to be taught extra about Castor canadensis, the exceptional four-legged engineers.

Household life

The North American beaver is the most important rodent within the Northern Hemisphere, usually weighing in at 35 to 65 kilos. (Solely the South American capybara weighs extra.) They make their houses in ponds, rivers, streams, and wetlands all through most of North America. 

long scene of beavers in a natural environment swimming, chewing wood and grooming


They’re one of many few species on the planet that usually mate for all times. Their offspring, often known as kits, can swim inside days of beginning, however their childhoods are among the many longest within the animal world. They typically reside for 2 years with their mother and father, which each participate in elevating them. It takes that lengthy for the mother and father and older siblings to point out them, by instance, tips on how to construct dams and lodges, tips on how to plan and dig channels, and tips on how to choose meals, harvest it, and retailer it for the winter. It’s sort of like going to engineering college. Beavers then transfer on to kind their very own households, usually constructing their very own colonies. They usually reside to age 10 or 12 within the wild. 

A well-planned weight-reduction plan

Beavers are vegetarians however with a twist. They favor the internal bark of sure tree species, together with willow, poplar, aspen, birch, and maple, feasting on the cambium, the gentle, sap-laden layer instantly underneath the outer bark. Conifers, nonetheless, will not be thought-about a delicacy. Beavers eat them solely not often, and have a tendency to fell them primarily for dam constructing and to encourage development of issues they’d moderately eat. In summer time they devour available grasses, leaves, herbs, fruit, and aquatic crops. To organize for winter in chilly climates, they create an underwater cache of sticks and logs they’ve gnawed from bushes they’ve felled. First they assemble a floating raft of not-so-delicious branches above a deep a part of their pond; then they stash their most popular branches beneath them. The pile absorbs water and sinks to the underside, with the less-favored branches usually freezing within the ice on the floor and appearing as a protecting masking that secures the more-desirable decrease branches, which stay accessible under the ice. The chilly water preserves the dietary worth of the branches. 

Whereas people can’t digest cellulose, beavers have a small sac between the massive and small intestines containing microorganisms that ferment this materials, serving to them digest as much as 30% of it.  

Reaching the proper pelt

Overlook mink, ermine, and sable. Of all fur-bearing animals, beavers have the coat that’s rated the warmest. So it’s no shock that European demand for hats made from heat, water resistant, and sturdy beaver felt led to profitable trapping and fur-trading ventures in North America. Within the 17th and 18th centuries, as many as 200,000 North American beaver pelts had been exported yearly to Europe. (Fierce competitors to monopolize the fur commerce led to a sequence of so-called Beaver Wars between 1628 and the Treaty of Montreal in 1701: the Iroquois Confederation, backed by the Dutch and British, battled the Huron Confederation, backed by France.) These enterprises gave rise to many European settlements and buying and selling facilities in North America—and practically worn out the continent’s beaver inhabitants. 

On January 17, 1914, MIT President Richard Maclaurin accepted the Know-how Membership of New York’s proposal that the beaver—nature’s engineer—function MIT’s mascot. In 1977, TIM the beaver first confirmed up on campus to rejoice the 50th reunion of the Class of 1927.

Beavers advanced to have such cozy pelts for good cause: they don’t hibernate, so they should keep heat and dry as they enterprise from their lodges into frigid waters to entry their winter meals cache. Sustaining such a pelt requires diligent grooming to take away particles and bugs and stop matting. A beaver rakes the fur of its face, head, and stomach with its fingernails, and will get at some difficult-to-reach spots with its hind toes. The innermost toenails on these toes open and shut over the toe, like a chicken’s beak, and performance as coarse-toothed combs. The second hind toe has a serrated attractive development between the true nail and the toe, which serves as a fine-toothed comb. Beavers waterproof their pores and skin and coats with oil produced by a pair of glands positioned beneath their tails and use these customized toenail combs to work it into their fur.

Beavers additionally have interaction in social grooming, often inside their lodge. A beaver’s physique is so spherical and its limbs so brief that it should depend on members of the family to groom its again. Mutual grooming additionally reinforces household bonds.

Getting round

Within the animal kingdom, beavers, people, bears, and the occasional ape are among the many few mammals that may maintain their our bodies upright and stroll for any distance. Like people, beavers can carry issues on the identical time, and infrequently stroll up from a pond onto their dam holding a rock, department, or clump of muddy clay with their entrance paws. Because of an opposing digit (the equal of the human pinky finger), they will grasp objects with their entrance paws, whose lengthy claws work nicely for digging. Additionally they use their “arms” to hold their kits and to carry and rotate meals as they gnaw it, much like how people eat corn on the cob. 

Beavers are glorious swimmers because of sturdy rear legs with huge, webbed toes. Additionally they profit from built-in swim goggles—an additional set of clear eyelids referred to as nictitating membranes that allow them see nicely underwater and shield their eyes from any harmful microorganisms in ponds and lakes. Beavers’ ears and nostrils can seal out water, and their giant lungs allow them to keep underwater so long as 15 minutes. 

A tail of many abilities

The form of a beaver’s tail runs within the household: some are brief and huge, others lengthy and slender. The tail presents an excellent instance of multifunctional engineering, permitting beavers to take care of stability, steer, talk, retailer meals, and extra.

When a beaver walks upright, carrying a heavy load like a rock or tree limb, its tail slides behind on the bottom, serving to the animal keep its stability. Within the water, the tail serves as a rudder and helps a swimming beaver maneuver previous obstructions.

Since sound travels nicely underwater, the beaver can sign an alarm to the colony by beating its tail on the water floor. And analysis means that beavers’ furless tails assist regulate physique temperature: conserving them in cool water on heat days permits the animals to keep away from overheating. 

In the course of the fall, the beaver shops a considerable amount of fats in its tail that it’ll use to complement its winter rations. Woodsmen and frontiersmen residing off the lean meat of untamed recreation treasured cooked beaver tail as a supply of fats in their very own weight-reduction plan.

Nature’s engineers

Along with having multifunctional tails, beavers come geared up with continuously replenished and self-sharpening reducing instruments. Their trademark entrance incisors are rusty orange because of an iron-rich enamel coating that helps them face up to mechanical stress and makes them immune to acid. And these tooth by no means cease rising. Beavers should repeatedly gnaw bark to maintain them sharp and to keep away from hunger. In the event that they don’t hold their incisors brief sufficient to shut their mouths, they will’t grind meals with their again molars. 

Beavers famously put these built-in instruments to good use constructing dams to show streams into ponds and swampy wetlands conducive to their lifestyle. (Like people, they’re on a really brief checklist of creatures that alter their setting to swimsuit their functions.) The typical beaver dam has a top differential slightly below 5 toes, however a minimum of one dam has been discovered with a 16-foot distinction between the water top behind the dam and in entrance of it. 

beaver in a box attached to a deployed parachute

After people and canine, beavers have essentially the most parachute jumps on document. In 1948, 76 beavers parachuted right into a distant space of Idaho as a part of a relocation program. Utilizing surplus World Battle II parachutes, they descended in packing containers that routinely opened upon touchdown.

When beavers dam rivers and streams, they have a tendency to decide on comparatively slow-flowing waterways and construct straight throughout. Like human engineers, they construct curved dams on extra swiftly flowing streams to higher face up to the stress of the dashing water. Beavers place about 50% to 70% of the wooden of their dams and let flowing water assist with the remaining: the remaining wooden (largely smaller sticks) will get trapped when it floats downstream. Though much less seen, river rocks the animals carry one after the other usually make up a significant portion of the dam. Beavers routinely examine and keep their dams, in order that they not often break.

The world’s longest recognized beaver dam is seen from area and was found by a researcher viewing satellite tv for pc photographs of a distant a part of Wooden Buffalo Nationwide Park in Alberta, Canada. Measuring 2,788 toes, it’s greater than twice so long as the Hoover Dam. Whereas human-built dams of that scale are constructed with huge, pollution-­spewing earth-moving tools, the Wooden Buffalo colony used simply their tooth and highly effective limbs—and the one air pollution concerned was emitted by the occasional “gassy” beaver. (By the way, whereas beavers do go gasoline, they’re incapable of burping.)

Beavers—which minimize a median of 216 bushes a yr and might topple a younger willow in six minutes—go to all this dam-building bother to gradual the move of water to allow them to create ponds during which to situate their lodges. The pond should be deep sufficient to maintain water from freezing all the way in which to the underside, permitting them to swim to achieve meals sources—and get out and in of their lodges—even in winter. 

To assemble a lodge in the course of their pond, beavers amass sticks, rocks, and dirt to create a platform about 10 centimeters above the water stage, topping that with a mound of sticks, bark, and extra mud. Then they dig tunnels from the mud under into the pile of sticks, and gnaw out a big, dry room above the waterline to create areas for feeding and resting. Typically, they’ll have a decrease room for consuming, topped by a drier room for hanging out and sleeping. 

Nationwide Geographic was available to doc beavers establishing each a dam and a lodge.

Generally beavers dig into the financial institution of a waterway to create a den, which might contain piling sticks on prime and gnawing out an area from the within. However siting a lodge so it’s surrounded by a moat of deeper water helps fend off giant predators like bears, which have problem breaking in if their again toes don’t have buy on stable floor. Whether or not in a financial institution or mid-pond, lodges are accessible solely from underwater tunnels, which presents safety from land-based predators. Usually, they’ve a minimum of two underwater entrances to make sure an escape route ought to aquatic predators like otters invade. 

Earlier than winter units in, beavers insulate their lodge partitions—which is usually a foot or two thick—by utilizing their entrance paws to coat them with mud, which freezes into a tough, plaster-like shell. A gap on the prime of the domed construction offers air flow.  

Beavers seem to have the ability to make the connection between flooding inside their lodge and the peak of water behind their dam. If the water will get too excessive, they may partially dismantle their dam to let water out and decrease the extent within the pond it incorporates. 

Beavers additionally dig canals and channels, which will be a number of hundred meters lengthy. Since most of their predators are at a drawback in water, they use canals to journey safely to faraway meals sources and logging websites in addition to to drift logs again to their pond for consuming and constructing. 

As environment friendly creators and stewards of wetlands, beavers present a hospitable ecosystem for dozens of different creatures, from bugs, frogs, and turtles to owls, otters, nice blue herons, and even moose and deer. What’s extra, by harvesting undergrowth for his or her dams and creating ponds and bogs that elevate the moisture content material of the soil, beavers reduce the chance that forest fires will unfold. As forest fires devastated Oregon in 2021, beaver wetlands remained inexperienced and plush, appearing as pure firebreaks. On aerial photographs of the charred panorama, the beaver’s habitat stands out, a large and verdant ribbon working via the blackened bushes.

Whereas not all property house owners who reside close to beaver habitats recognize the animals’ tree removing companies, the pro-­beaver motion appears to be getting extra organized. In November 2023, some 300 beaver restoration advocates from North America and Europe gathered within the Beaver State (Oregon) for the annual State of the Beaver convention. “Seventy-five % of the bogus wetland restoration initiatives completed in America over the previous 30 years have failed,” convention cofounder Stanley Petrowski instructed the Day by day Yonder. “However when beavers do it, they do it completely.” 

BeaverCon, held close to Baltimore in June of 2022, and the Midwest Beaver Summit, held in Chicago and on-line in September 2023, attracted related crowds of people eager about selling beaver welfare.

It’s, in reality, doable to search out methods to permit beavers to proceed creating their watery habitats in ways in which decrease injury to human infrastructure. For instance, units such because the Beaver Deceiver will be put in to forestall beavers from damming culverts, which regularly results in flooding of roads. Skip Lisle, founding father of Beaver Deceivers Worldwide of Grafton, Vermont, first developed the system within the 1990s to beaver-proof the Penobscot Nation’s 130 miles of roads in Maine. “In all chance, they’re the primary giant landowner to fully beaver-proof their property nonlethally,” he says.

Residing natural chemical manufacturing facility

On the base of their tail, all beavers have two castor sacs that retailer castoreum, a fancy, granular substance with a powerful and long-lasting musky odor. It’s made up of a minimum of 24 totally different compounds, primarily derived from the barks of the assorted bushes within the beaver’s weight-reduction plan. Beavers deposit castoreum atop foot-high mounds of mud, sticks, and grass to mark the perimeters of their territory. 

People have lengthy valued castoreum. About 400 BCE, Hippocrates, a chronicler of pure cures, wrote of its fantastic medical properties. Round 77 CE, the Roman naturalist Pliny listed castoreum as a treatment for complications, constipation, and epilepsy. Within the Center Ages the checklist of maladies castoreum was mentioned to treatment expanded to incorporate dysentery, worms, fleas, pleurisy, gout, rheumatism, insomnia, hysteria, reminiscence loss, and liver issues. 

old black and white photo of William Miller in a canoe
Writer William Miller ’51, SM ’52, stories that his foot as soon as crashed via a beaver dam whereas he was dragging his canoe over it to get to the following lake in Jasper Nationwide Park in Alberta, Canada. About 100 toes away, a watching beaver
instantly started to slap its tail on the pond floor. Having simply unleashed a string of curses directed on the beavers, Invoice assumed that the beaver was
cursing at him. However he now suspects it was sending a warning sign to the opposite beavers—or probably urging them to return shortly to restore the injury brought on by the trespassing human oaf.

Because it seems, fairly just a few of the tree barks that beavers favor comprise compounds with recognized medicinal advantages. Phenols, for instance, are sometimes anti-­inflammatory and antiseptic and might have antiviral properties. They embody salicylic acid (a precursor to aspirin), which will be discovered within the bark of willow, poplar, and alder bushes—all beaver favorites. The beaver’s system features as a pure pharmacy, extracting these compounds (amongst others) and secreting them within the type of castoreum. 

People have additionally used castoreum for a number of nonmedical functions, comparable to in high-end “leather-based word” perfumes together with Shalimar, Givenchy III, and Chanel’s Antaeus. It’s an ingredient in some bourbons and vodkas and has been utilized in Sweden to taste “Bäverhojt” (actually, beaver shout) schnapps.

At the moment, most castoreum is harvested in a sterile setting by anesthetizing beavers and expressing the castor sacs close to their tails. As a meals additive, castoreum extract is “typically acknowledged as protected,” based on the FDA. However at near $100 per pound, it’s used sparingly. The full annual US consumption of dried castoreum is round 300 kilos.

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