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

Beavers, otters, and more – new Conaway Ranch game camera footage!

By Geoff Benn • June 4, 2026
A beaver at Conaway Ranch We’ve got new footage from our game cameras at Conaway Ranch! This camera site was chosen by 4 th graders from Dingle Elementary during a recent field trip to Conaway. The camera is near the otter slide we’ve previously filmed, but is a few feet away from the entrance to the slide, allowing us to film the animals as they approach. We saw beaver, otter, a fox, a raccoon, and more! Click here to watch the video . Tuleyome works with Conaway Preservation Group to offer educational programs at Conaway Ranch, including programs for K-12 groups and the general public. If you have any questions about the game camera footage or our programs at Conaway, please reach out to Education Associate Geoff Benn at gbenn@tuleyome.org.

Policy Corner: It’s Time to Fight for Our Public Lands

June 4, 2026
The current administration has released its proposed budget for the 2027 fiscal year. It proposes drastic cuts to our public land management agencies. The proposed budget would significantly reduce funding for the Bureau of Land Management (BLM), including a 34% cut to its total budget, a 27% staff cut, a 76% cut to the National Conservation Lands, which encompass 38 million acres of protected public lands, a 61% cut to recreation management (including campsites and trails), and total elimination of funding for cultural resources and wilderness management. It also would shift priorities towards extractive uses of public lands instead of conservation and clean energy. The administration’s budget would also drastically cut funding to the U.S. Forest Service (USFS), eliminate several offices, state and federal research stations (six in California) and transfer all fire fighting to BLM. Notably, in the face of all these cuts, the budget would increase funding for extractive industries; funding for timber sales would increase 450%. The reductions and policy changes would impair these agencies’ abilities to protect public lands, cultural resources, fresh water sources, and wildlife, while also impairing access to them and recreation on them. The President’s budget is now in Congress, where committees in both the Senate and the House of Representatives are amending and voting on the bills in preparation for full House and Senate votes. Now is the time to take action for our public lands and the environment by urging Congress to reject the proposed budget and maintain funding for BLM, USFS, and programs that protect and steward our public lands. Let your representatives know that you oppose the cuts to BLM and USFS and the rollbacks to our public land protections. And let them know why these special places are important to them. You can voice your opinions to Congress in multiple ways. You can: Call their offices Send a letter to Congress - we’ve pulled together a template for you to use, but don’t forget to let them know why public lands are important to you – download sample letter here Contact them on social media Meet with a representative in their District offices. Don’t know how to reach them, go to Congress.gov and find their phone numbers, addresses, district offices, websites and so much more if you’re interested. Now is the time to speak up for our public lands! Mary Lamborn (Communications Intern) and Sandra Schubert (Executive Director)

Monumental Questions - Another Monumental Vegetable?

By Kristie Ehrhardt • June 4, 2026
You betcha! Wild carrot, also known as Queen Anne’s Lace, is a common sight within the Berryessa Snow Mountain National Monument region. With its straight and sturdy stalk, bright green, frilly leaves and white, flat-topped flower clusters, it is identifiable even from the limited viewing scope of a traveling car. Queen Anne’s Lace ( Daucus carota ) belongs to the Apiaceae (carrot) family. All members of this family display flower clusters arranged in an upside-down umbrella shape called an umbel. It is native to Europe and is the plant that tasty cultivated carrots originated from. It was brought to North America for its medicinal purposes and has since naturalized across the continent in disturbed and natural areas in mountains, valleys and coastal areas. It can be so prolific that it outcompetes native plants and can also be mildly toxic to livestock. Queen Anne’s Lace is an herbaceous biennial (it doesn’t flower until its second year and then dies) that can reach up to four feet tall in optimum conditions. The stem of the plant is bright green, straight and sturdy and is covered in short, coarse hairs which is a very helpful identifier. I recently learned a clever and helpful quip that I will never forget: Queen Anne has hairy legs (referring to the hair along the stems of the plant)! The tiny, white flowers all originate from the same point and splay out in an airy, flat topped cluster (umbel). Another identifying feature is that oftentimes (but not always) the flower umbels often have a single dark purple flower in the center of the cluster. This purple flower is not always present but when it is it can be used to positively identify the plant as Queen Anne’s lace. The leaves are finely divided which gives them a lacy appearance and look almost identical to our cultivated carrot plants. Although wild carrots are edible, the whitish tap root isn’t as robust or flavorful as the cultivated carrots we are used to. Warning! There are plants such as poison hemlock that are incredibly similar looking so eating things in nature is never advised unless you can absolutely identify them! Poison hemlock has basically the same growth pattern as wild carrot however the stem of poison hemlock lacks the tiny hairs and mature plants have very definite purple splotches up and down the stems. All parts of poison hemlock are toxic but it is particularly potent in the seeds and roots. Poison hemlock is notoriously known as the poison that killed the Greek philosopher Socrates. Edible cousins of wild carrot include plants such as caraway, celery, parsley and parsnips. Although the root of the wild carrot plant is edible, contact with the sap may produce an allergic reaction in some individuals that are sensitive to it. Native pollinators such as butterflies and bees appreciate the abundance of flowers for their nectar. Wild carrot is currently blooming in all its glory so keep an eye out for it on your next trip to our favorite monument!