If you’re a Far Side fan, you might remember this one: There’s the beaver husband sitting in his chair in the living room, wanting to read the paper but having to give his wife a sideways I’m-a-little-piqued-that-you’re-talking-about-me sort of look instead. She, a typical FS lady of a certain age, is wearing cat-eye glasses, an apron, and an exasperated expression. She’s on the phone. “No, he’s not busy,” she’s saying. “In fact, that whole thing is just a myth.”

Spousal dynamics aside, this particular guy is likely an aberration, because beavers are, in reality, very busy. They are what is known as a keystone species—that being a species with outsized ecological impacts relative to their biomass—and are a critical link in the ecosystem scheme of things, particularly when it comes to water. One of my buddies who is a fishing freak got very excited when I told him I was writing about beavers for the Fishue. “Beavers and trout are like this,” he said, holding up one hand with his index and middle finger entwined. That close. No myth.

Beavers are second only to humans in their ability to manipulate their environment. Think about that for a minute. They modify their habitat to suit their needs, but, in their case, the end result is often very beneficial to the biodiversity of said habitat. We can’t always make that claim.

Castor canadensis is the second largest living rodent, with South America’s capybaras holding first place. Adults range in weight from forty to sixty pounds, with an average length of forty inches. Those famous, flat, paddle-like tails are typically eight to twelve inches long and six inches or so wide. In the water, beavers use them as a rudder, a propeller, and to make a loud noise in case they need to get the attention of their compatriots. On land they’re useful as support while the animal is munching away on roots or twigs. They’re a fat storehouse during the winter months.

Beavers’ hind feet are webbed; their front feet are hand-like and dexterous. Their front teeth grow continuously. (Do the teeth grow because the beavers eat trees or do the beavers eat trees because their teeth don’t stop growing?) Baby beavers, known as kits, are born with teeth already through the gums. Beavers eat grass, ferns, mushrooms, stems, roots, and various tree parts. (Another great Far Side cartoon shows a beaver standing in front of an open refrigerator. The shelves are full of limbs and branches.) Beavers are monogamous; mom, dad, and children live together until the kids are about two, then it’s out you go, find your own territory. Failure to launch is not a beaver option.

By the end of the nineteenth century, uncontrolled trapping (beavers have great fur, which looks best on them, IMO) and habitat loss had eliminated beavers in Pennsylvania and in most of the rest of the country. They’ve since been successfully reintroduced. In the late 1940s, the state of Idaho used surplus military parachute equipment to get beavers into remote areas where their engineering skills would help with needed water retention. These days they can be found throughout the continental United States and Canada, except in some desert areas. The largest beaver dam in the world—about half a mile long—is in Alberta. It holds the equivalent of 92,000 dump trucks full of water, and can be seen from space.

So how is it that “beavers and trout are like this?” Water and bugs.

Beavers have some natural terrestrial predators, so their go-to safe space is the water. The ponds they create provide protection from those land-based hunters, but, even though a beaver can stay under water for fifteen minutes, even though they can close their lips behind their teeth so they can transport sticks and other food and not drown, they can’t swim forever. So they make lodges for shelter and protection, for rearing their babies, and for a place to live during the winter. But it’s their ponds, dams, channels—their engineering, their changing their habitat to suit their needs—and the resulting wetlands that serve as such an impressive ecological benefit to other species. According to one statistic, the riparian zone around beaver activity sees an increase of over 33 percent in the number of herbaceous plants—those are plants with flexible green stems and few to no woody parts, and they’re a salad bar for the critters who live on them. The watery habitats they create provide living space and food for insects (the kind trout like), amphibians, fish, waterfowl, owls, mink, and otters. Their dams serve as water impoundments—i.e. fish habitat—during droughts, and they are natural filtration systems. There are measurable increases in aquatic and terrestrial biodiversity around beaver ponds and their surrounding riparian habitats.

A study by the Yale Environment Review estimates that beavers have the capacity to provide close to half a billion (yup, that’s a “b”) dollars of value in ecosystem services. As we’ve done in the past with more than one species, our propensity for near decimation leads to an “oops, maybe we shouldn’t have done that” moment, followed by successful reintroduction, followed by a need to “manage” a population. Beavers’ presence and engineering prowess are not always welcome. Sometimes they build dams and make ponds where those features are not wanted, or they munch down on trees we’d rather they left alone. Heavy gauge fencing around trees can offer some protection, and water level control devices can minimize the sound and motion of running water, both of which can lead to in an irresistible urge on the beaver’s part to start a construction project.

Trapping, legal in Pennsylvania December through March and in New York November through April, is the most common method of population control. Or, we, as the master manipulators, could maybe learn to live with them.