Science Corner - North American Beaver (at Conaway Ranch!)

Kristie Ehrhardt • June 5, 2025


The North American Beaver also commonly called American Beaver, Canadian Beaver or just beaver is the largest member of the rodent family in the United States. The word rodent means “to gnaw” and rodents are characterized by a pair of continuously growing upper and lower incisors. Beavers must constantly gnaw on trees to keep their teeth from getting too long. About 40% of all known mammal species are rodents and are native all over the world with the exception of Antarctica.

 

It is believed that beavers are from ten to twelve million years old and fossils were first discovered in Germany. It is thought that these beavers used the Bering Strait to reach North America about seven million years ago. Today there are two distinct species of beaver; the American Beaver (Castor canadensis) and the Eurasian Beaver (C. fiber). The American Beaver is the species found in the United States and the rest of North America.

 

American Beavers (beavers) are semi-aquatic spending at least part of their day in water. Their tails are large, flat and paddle-shaped and when combined with their webbed hind feet, beavers are excellent swimmers. Beavers also use their flat tails to slap the water to signal danger to other nearby beavers, to store fat and to help them balance when toting loads of heavy logs and branches. Beavers' front feet are smaller than their rear feet and have claws rather than being webbed. Their front feet are extremely dexterous and give them the ability to grasp and rotate pencil-thin stems, peel off bark, dig and put food such as small leaves in their mouths. Another adaptation of semiaquatic life includes a nictitating membrane which covers and protects the eyes so they can remain open under the water allowing them to see and ears and nostrils that are able to seal shut while under water. Despite their large incisors, beavers are able to close their mouths over their teeth. Beavers range from about 25 pounds to over 70 pounds but the average is around 50. They are about 30 to 35 inches from nose to rump with tails that range from eight to nearly 14 inches long. Beavers sport a rich, dark chocolate-brown double coat which includes long, coarse outer hairs and short, fine and dense inner hairs. This coat helps keep the beaver’s body dry and insulates it from cold and hot temperatures. Beavers have two sets of scent glands. One set produces an oily substance called castoreum (which is where the beaver’s Genus, Castor, comes from and is used to waterproof their coats. The other set of scent glands produces waxy chemicals that help identify one beaver to another. Beavers also have a thick layer of fat just under their skin that also helps keep them warm while in cold, sometimes icy water. Beaver fur was so sought after at one point in time that they were nearly driven to extinction.

 

Beavers are primarily nocturnal but can also be active during the day and spend their time going to and from water collecting bark, leaves, roots and wetland plants to eat. They excel at swimming and can remain underwater for up to 15 minutes. Which is advantageous because they spend an awful lot of their time designing and building their homes and water control structures. Beavers build their dwelling or lodges using rocks, sticks and mud in waterways and other bodies of water. Their lodges may be juxtaposed to land or surrounded entirely by water. The inside of the lodge is covered with mud which dries to the consistency of cement keeping the lodge warm and dry during the cold, wet months. A breathing hole is left open at the top of the lodge and entrances are underwater. Lodges have multiple chambers and different elevations to keep them either moist for feeding or warm and dry for sleeping. Beavers also build dams in order to back up water and form deep ponds to allow for the beaver to escape predation from coyotes, wolves, mountain lions and other top predators. Dams are built using longer branches, vegetation and mud. If tree branches and vegetation are not available beavers will use rocks to build their dams. Branches, sticks, twigs and vegetation are cut using their incisors and carried and put in place using their front feet. Dam building not only provides a refuge for the beavers but it also creates and enhances habitat for other amphibians, fish and waterfowl. Beaver dams also help reduce soil erosion and may lessen the impacts of flooding.

 

Beavers are monogamous and mate at about three years of age. Only one litter of one to four kits is born a season and usually remain with their parents inside the warm, safe lodge for up to two years.

 

Beaver Facts : 

  • At one point beaver fur was so valuable, primarily for hats and shirts that the species was on the brink of extinction. Today it is estimated that there are about 10-15 million American Beaver occurring throughout its range in North America and are considered invasive species in some places!
  • Very old beavers can weigh over 100 pounds (about the weight of a king size mattress)!
  • It’s believed that the sound of running water is what urges beavers to build or repair their dams. The largest beaver dam was discovered by satellite imagery in 2007 near Alberta, Canada. It was nearly a half a mile long and two times wider than Hoover Dam!
  • Beavers are considered “keystone species” because their activities provide increased biodiversity by forming or enlarging wetlands and surrounding riparian habitats - they are unique in that they can change the landscape!

 

Be sure to check out Tuleyome’s Youtube channel for a very close up (!) view of beavers and other wildlife friends at play at our partner in conservation Conaway Ranch!


-Kristie Ehrhardt (kehrhardt@tuleyome.org)

Tuleyome Land Conservation Program Manager

RECENT ARTICLES

June 5, 2025
We extend our thanks and gratitude to Stephen McCord as he ends his tenure on the Tuleyome Board of Directors. Stephen has applied his energy and expertise to fulfilling Tuleyome’s mission for many years. In 2016 he managed the first Tuleyome mercury mine remediation project at the Corona/Twin Peaks Mine. He followed that with work on Tuleyome trail projects in the Knoxville Off-Highway Vehicle Area, riding all the trails on his own adventure motorcycle. As a Tuleyome representative, he’s taken many community members on hikes in Berryessa Snow Mountain National Monument and the surrounding areas. Stephen has over 20 years of environmental engineering experience, in California and worldwide. He has overseen extensive projects in water quality field work, management and cleanup, and has applied his knowledge to policy development, analysis and technical support. In short, Stephen is a consummate environmental and water engineer, and he brought his expertise to Tuleyome’s many projects. In 2023 Stephen joined the Board of Directors and agreed to serve as President. He applied his supreme organizational skills to managing board duties and activities. He also brought an optimism to the board about what can be accomplished with foresight, good planning and collaboration. Stephen has been a tireless advocate for Tuleyome, keeping the board on task even while handling numerous other professional responsibilities. Fortunately, although he is stepping down from the board, he will continue to support Tuleyome’s mission in many other ways. -Kim Longworth, Lyndsay Dawkins and Bill Grabert Volunteer Tuleyome Board members 
By Geoff Benn June 5, 2025
A river otter making its way up the slide. Looking to take a break with some cute video content? This month we placed game cameras looking into an otter slide at Conaway Ranch. Otter slides are paths worn into riverbanks by repeated use by otters and other animals. The slides at Conaway are quite active, so we’ve been able to get some great footage, including otters, beavers, racoons, snakes, and more! 
By Bryan Pride June 5, 2025
Since April 2024, America's public lands had something they'd never had before: a rule that treated conservation as equal to all other land uses. The Public Lands Rule , introduced by the Biden Administration, formally recognized conservation as a legitimate practice of multiple use, putting conservation on equal footing with recreation, grazing, and resource extraction. Built on decades of management experience and guided by science, data, and Indigenous knowledge, it gives land managers tools to maintain healthy ecosystems while supporting all the diverse ways we depend on public lands. It acknowledges a simple truth: conservation must be valued equally to all other land uses. Now there is growing pressure to rescind it. Why This Matters The environment around us is free-flowing, it's not confined to state borders or county lines. When mining operations contaminate watersheds in Northern California, it impacts the local businesses who depend on healthy rivers downstream, the agricultural communities that rely on clean water, and the families who've been camping along those waterways for generations. The Public Lands Rule recognized this interconnected reality and gave land managers agency to address problems before they spread across California's diverse landscapes, protecting the long-term viability of grazing allotments, recreation areas, and rural livelihoods that all depend on healthy public lands. This interconnected reality is exactly why the Public Lands Rule matters. The Rule is designed to ensure that the places we depend on, whether for weekend camping trips, or cattle grazing, stay healthy enough to support these uses long-term. When an area becomes overgrazed and doesn't recover, access to those grazing allotments is permanently lost, reducing ranchers' ability to maintain their livelihoods and harming local food production. Poor use or overuse of our public lands creates ripples of negative impact that hurt all communities. The Rule's main objective is simple but revolutionary: make sure our public lands stay productive for everyone who depends on them, rather than degrade them. The Rule created practical tools that built in accountability and prioritized future generations' access to healthy public lands. Restoration Leases : 10-year agreements allowing a variety of entities such as, conservation groups, tribes, and nonprofits to restore damaged landscapes—fires restoration, restoring wildlife habitats and cleaning up abandoned mining sites that currently scar some of our most beautiful public lands. Mitigation Leases : A tool that allows land users or other entities to offset impacts from their activities over specified time periods, creating partnerships between different land users and conservation groups to address environmental impacts on public lands. Strengthened Protection for Critical Areas : Clearer guidelines for protecting Areas of Critical Environmental Concern—the most special and fragile places that often provide the best wildlife viewing, the cleanest water sources, the most pristine camping experiences and the richest biodiversity. The False Dichotomy: Multiple Use vs. Conservation The main argument being used to encourage the rollback of the Public Lands Rule is " multiple use ", the legal principle requiring Bureau of Land Management (BLM) lands to serve many different purposes. The current Administration claims the Public Lands Rule hinders multiple uses of public lands. Why? The Rule calls for restoring degraded areas and making science based decisions. Contrary to their actual meaning, the current Administration interprets "restoring" and "science based decisions" as "locking up land". Land locking, where access gets completely cut off, is a real concern in some areas—it prevents both recreation and grazing. However, land locking is not what the Public Lands Rule promotes. In reality, it is promoting land healing. Take grazing for example. The Rule empowers BLM to use restoration leases in conjunction with existing grazing permittees to restore degraded rangeland. Monitoring who is grazing where and the number of permits issued for specific areas is a means to ensure sustainable grazing and prevent overuse. Many ranchers and land managers supported the Rule because they understand that healthy land is productive land. Overgrazing and environmental damage hurt their livelihoods too. The same principle applies to fire recovery. When public lands are damaged by sweeping wildfires, there is a need for active restoration: replanting native vegetation, stabilizing soils, removing hazardous debris. Restoration has to take place before safe recreation, grazing and other uses can resume. At times, restoration requires temporarily limiting access to burned areas as they recover. The goal is to allow for our lands to recover and heal before we start depending on them again with our multiple uses. Land restoration is not just limited to grazing or extraction; it is essential for recovering from wildfires. Whether it's grazing, recreation, or extraction, the Public Lands Rule isn't about stopping these uses, it's about understanding that healthy ecosystems are prerequisites for multiple use, not obstacles to it. You can't have sustainable grazing on degraded rangeland, quality recreation in fire damaged landscapes, or responsible extraction without considering long-term impacts We Are Public Stewards The Public Lands Rule represents a historic shift in how we value conservation, its potential rollback is a setback. But the vision it represents, conservation as a form of legitimate multiple use, remains essential and is not gone. As stewards of these 245 million acres, we have the power to practice conservation in our own actions and advocacy. Every time we practice Leave No Trace, support local businesses that operate responsibly on public lands, and make our voices heard in land management decisions, we're building the foundation for balanced stewardship that benefits everyone. Our public lands belong to all of us, which means we each have the power, and responsibility, to be good stewards of the lands we love. -Bryan Pride ( bpride@tuleyome.org ) Certified California Naturalist Policy Director