Monday, June 17, 2019

Episode 477 (6-17-19): Beavers Change Habitats and (Sometimes) Challenge Humans

Click to listen to episode (4:50).

Sections below are the following:
Transcript of Audio
Audio Notes and Acknowledgments
Extra Information
Related Water Radio Episodes
For Virginia Teachers (Relevant SOLs, etc.).

Unless otherwise noted, all Web addresses mentioned were functional as of 6-14-19.


From the Cumberland Gap to the Atlantic Ocean, this is Virginia Water Radio for the week of June 17, 2019.

SOUND - ~ 3 sec – Beaver tail splat and splash

This week, those mystery sounds open a revised episode from 2012 on a semi-aquatic mammal known for its teeth, its tail, its fur, and its behavior.  Have a listen for about 10 more seconds, and see if you can guess what’s making the splat and splash sounds.  And here’s a hint: You can guess this if you get BUSY.

SOUNDS - ~8 sec – Beaver tail splat and splash, twice

If you guessed a beaver, you’re right! That was the sound of an American Beaver smacking its tail on the surface of a creek as the animal submerged.  The tail slap is a defensive behavior for a beaver protecting the territory around its colony.  As semi-aquatic mammals, beavers spend time both on land and in the water, in contrast to fully aquatic mammals like dolphins or whales.  Beavers live in lodges that either are dug into the banks of streams, lakes, or ponds, or are built freestanding from wood and mud, with interior spaces above water and entrances below water.  Beavers build dams to deepen the water level for lodge building, but also to allow the animals to dive for safety, travel in the water to feeding areas, and transport felled trees back to their lodge.  Beavers feed on bark from various tree species as well as on non-woody plants when those are available.

Beavers have many adaptations for their semi-aquatic life.  The paddle-like tail, besides its use in warnings, functions in propulsion and maneuvering in the water, balance while feeding on trees on land, fat reserves, and body temperature regulation.  The front feet are adapted for grasping food and digging, while the webbed hind feet aid in swimming.  When a beaver is underwater, valves keep water out of the nose and ears, transparent membranes cover the eyes, and the lips close behind the teeth, allowing underwater gnawing.  And beaver fur keeps in heat, keeps out water, helps the animal float, and provides protection from predators.

That fur’s use in hats and other products made the animals highly prized, widely trapped, and historically significant during European exploration and settlement of North America, to the point that beavers were eliminated from much of their natural range.  But reintroduction and successful reproduction have restored beaver populations to much of North America, including throughout Virginia.  The return of beavers to developed areas presents humans with a range of benefits and costs.  Beaver activity can create new wildlife habitats and have positive impacts on water quality, but it can also result in flooded human infrastructure, eating of agricultural crops, and damage to trees.

Living on land and in the water; having a significant role in the history of North America, affecting wildlife and human habitat: the American Beaver is a complicated wildlife story.  Here’s a closing take on that story, from Dietland Müller-Schwarze, in his 2011 book, The Beaver: Its Life and Impact: “This animal dazzles with its extensive constructions, demands respect as a survival artist, and—when in conflict with humans—challenges the best minds in wildlife management.  Many citizens’ groups and professionals strive to resolve those conflicts and find ways for us to coexist with beavers.”


Virginia Water Radio is produced by the Virginia Water Resources Research Center, part of Virginia Tech’s College of Natural Resources and Environment.  For more Virginia water sounds, music, or information, visit us online at, or call the Water Center at (540) 231-5624.  Thanks to Ben Cosgrove for his version of “Shenandoah” to open and close the show.  In Blacksburg, I’m Alan Raflo, thanking you for listening, and wishing you health, wisdom, and good water.


This Virginia Water Radio episode revises and replaces Episode 113, 6-4-12.

The sounds heard in this episode are from a video recording by Virginia Water Radio at Toms Creek in Heritage Park in Blacksburg, Va., on June 2, 2012.  A 23-second segment of that video is available on YouTube at

Click here if you’d like to hear the full version (2 min./22 sec.) of the “Shenandoah” arrangement/performance by Ben Cosgrove that opens and closes this episode.  More information about Mr. Cosgrove is available online at


Three photos above: the beaver heard in this week’s episode, photographed at Toms Creek in Heritage Park in Blacksburg, Va., June 2, 2012.

Beaver lodge along Appalachian Trail at U.S. Route 42 in Giles County, Va., December 31, 2015.

Beaver dam on a tributary to Toms Creek in Heritage Park in Blacksburg, Va., January 2005.


The scientific name of the American Beaver (also referred to as the North American Beaver) is Castor canadensis.

Following is information about the American Beaver excerpted from the Virginia Department of Game and Inland Fisheries, “Fish and Wildlife Information Service/American Beaver,” online at, accessed 6/14/19.

Physical Description

“This is a heavily built animal, with short legs, webbed hind feet and a horizontally flattened and scaly tail. The second digit is split, and they have short rounded ears. The fur is glossy dark brown above, with lighter under parts, and the tail becomes lighter with age. The eyes are small, and the front feet have strong claws adapted for digging and grasping tree limbs. …The lips close behind the front teeth keeping water from entering the mouth when they are cutting branches under water.”


“They breed in mid-January to late February or March. …They are well developed at birth: furred, eyes open, average weight 340-630 grams, inversely related to litter size. …They have moved 150 miles from the birth place, but usually begin their own colony within a few miles. They are known to range more than 450 feet from water in search of food, but usually stay much closer. The fundamental unit of population is a colony of 4-8 related individuals. The colony defends the territory against other colonies.”

Behavior and Habitat

“This species is primarily nocturnal, with some crepuscular. …When possible beavers construct dams to form ponds in which they build their lodge. If a dam is not feasible they will dig 10-40 foot long by 1-1.5 feet wide tunnels into the bank. …Water, and the availability of food…are important determinants of habitat suitability. They are also not usually found in stream/river headwaters due to the steep gradient and rocky bottoms.”

“The territory is defended by scent mounds, and tail slapping. The lodges made of wood and mud usually have 2 or more underwater entrances and a chamber a few inches above water level. …They can stay under water at least 15 minutes, but 1-2 minutes is average. Beavers influence vegetation by selective tree cutting (timber destroyed is mostly low-grade), elevating water tables and hastening or impeding succession of the adjacent forest. …The ponds created can act as catch basins, and may provide water for irrigation.”

Following is additional information from the Virginia Department of Game and Inland Fisheries, “Wildlife/Beaver,” online at, accessed 6/14/19.

“The beaver is North America’s largest rodent.  Adult beavers normally weigh 40 to 50 pounds, but exceptionally large animals may weigh up to 80 pounds.  They range in length from 35 to 50 inches, including the tail, which normally is about 10 inches long.  Beavers today are found throughout North America. Here in Virginia, biologists believe beavers are present in every county.  Beavers are important in that they create new habitats that benefit a variety of other animals.  Their dams slow the flow of moving waters and allow other wildlife and plant species to colonize this modified ecosystem.  Ducks and other waterfowl, as well as many reptiles, amphibians, and aquatic insects, are attracted to beaver ponds.  However, the impaired flow and removal by beavers of the woody vegetation along the shoreline can raise the water’s temperature and allow more sediment to collect behind the dam.  Lower dissolved oxygen levels and higher water temperatures may favor some organisms, but at the expense of others (e.g., trout and aquatic insects dependent upon cool, flowing waters).  Physical damage caused by beavers in the Southeast is estimated in the millions of dollars annually.  Examples of this damage include timber and agricultural crop loss, damage to roads, septic systems and other property by flooding, and destruction of ornamental plants used in landscaping.”


Karl Blankenship, “Can beavers help build a better Chesapeake Bay?”  Bay Journal, January 24, 2022.  [Added 4-14-22]

Center for Wildlife-Human Conflict at Virginia Tech, “Beaver,” online at

Frank E. Fish, “Biomechanics and Energetics in Aquatic and Semiaquatic Mammals: Platypus to Whale,” Physiological and Biochemical Zoology, Vol. 73, No. 6 (November/December 2000), pp. 683-698; accessed online at

Patricia Maria Graf et al., Diving behavior in a free‐living, semi‐aquatic herbivore, the Eurasian beaver Castor fiber, Ecology and Evolution, Vol. 8, No. 2, January 2018, pp. 997–1008; accessed online at

Dietland Müller-Schwarze, The Beaver: Its Life and Impact, Second Edition, Cornell University Press/Comstock Publishing Associates, Ithaca, N.Y., 2011.  The passage quoted in this episode is from page vii of the Preface.

National Oceanic and Atmospheric Administration (NOAA)/National Ocean Service, “What’s the Difference Between Dolphins and Porpoises?” online at,

Alan Raflo, “If They’re in Your Neighborhood, Beavers Can Be Big News,” Virginia Water Central Newsletter, April 2005 (pp. 14-15), Virginia Water Resources Research Center, Blacksburg, Va.; available online at

Smithsonian’s National Zoo and Conservation Institute, “Beaver,” online at

Virginia Department of Game and Inland Fisheries, “Fish and Wildlife Information Service/American Beaver,” online at

Virginia Department of Game and Inland Fisheries, “Wildlife/Beaver,” online at


All Water Radio episodes are listed by category at the Index link above (  See particularly the “Mammals” subject category.


The episode—the audio, extra information, or sources—may help with the following Virginia Standards of Learning (SOLs).

2010 Science SOLs

Grades K-6 Scientific Investigation, Reasoning, and Logic Theme
2.1, 3.1, 4.1, 5.1, and 6.1 – Current applications to reinforce science concepts.

Grades K-6 Earth Resources Theme
4.9 – Va. natural resources, including watersheds, water resources, and organisms.
6.9 – public policy decisions related to the environment.

Grades K-6 Life Processes Theme
K.7 – basic needs and processes of plants and animals.
1.5 – animals’ basic needs and distinguishing characteristics.
3.4 – behavioral and physiological adaptations.

Grades K-6 Living Systems Theme
2.5 – living things as part of a system, including habitats.
3.6 – ecosystems, communities, populations, shared resources.
4.5 – ecosystem interactions and human influences on ecosystems.
6.7 – natural processes and human interactions that affect watershed systems; Va. watersheds, water bodies, and wetlands; health and safety issues; and water monitoring.

Life Science Course
LS.1 – understanding of scientific reasoning, logic, and the nature of science, including current applications to reinforce science concepts.
LS.8 – community and population interactions, including food webs, niches, symbiotic relationships.
LS.9 – adaptations for particular ecosystems’ biotic and abiotic factors, including characteristics of land, marine, and freshwater environments.
LS.10 – changes over time in ecosystems, communities, and populations, and factors affecting those changes, including climate changes and catastrophic disturbances.
LS.11 – relationships between ecosystem dynamics and human activity.

Earth Science Course
ES.8 – influences by geologic processes and the activities of humans on freshwater resources, including identification of groundwater and major watershed systems in Virginia.

Biology Course
BIO.1 – current applications to reinforce science concepts.
BIO.8 – dynamic equilibria and interactions within populations, communities, and ecosystems; including nutrient cycling, succession, effects of natural events and human activities, and analysis of the flora, fauna, and microorganisms of Virginia ecosystems.

Virginia’s SOLs are available from the Virginia Department of Education, online at

Following are links to Water Radio episodes (various topics) designed especially for certain K-12 grade levels.

Episode 250, 1-26-15 – on boiling, for kindergarten through 3rd grade.
Episode 255, 3-2-15 – on density, for 5th and 6th grade.
Episode 282, 9-21-15 – on living vs. non-living, for kindergarten.
Episode 309, 3-28-16 – on temperature regulation in animals, for kindergarten through 12th grade.
Episode 333, 9-12-16 – on dissolved gases, especially dissolved oxygen in aquatic habitats, for 5th grade.
Episode 403, 1-15-18 – on freezing and ice, for kindergarten through 3rd grade.
Episode 404, 1-22-18 – on ice on ponds and lakes, for 4th through 8th grade.
Episode 406, 2-5-18 – on ice on rivers, for middle school.
Episode 407, 2-12-18 – on snow chemistry and physics, for high school.