Environmental impacts of beavers
The
Effects on stream flows and water quality
Beaver ponds increase stream flows in seasonally dry streams by storing run-off in the rainy season, which raises groundwater tables via percolation from beaver ponds. In a recent study using 12 serial aerial photo mosaics from 1948 to 2002, the impact of the return of beavers on openwater area in east-central Alberta, Canada, found that the mammals were associated with a 9-fold increase in openwater area. Beavers returned to the area in 1954 after a long absence since their extirpation by the fur trade in the 19th century. During drought years, where beavers were present, 60% more open water was available than those same areas during previous drought periods when beavers were absent. The authors concluded that beavers have a dramatic influence on the creation and maintenance of wetlands even during extreme drought.[5][6]
From streams in the Maryland coastal plain to Lake Tahoe, beaver ponds have been shown to remove sediment and pollutants, including total suspended solids, total nitrogen, phosphates, carbon, and silicates, thus improving stream water quality.[7][8] In addition, fecal coliform and streptococci bacteria excreted into streams by grazing cattle are reduced by beaver ponds, where slowing currents lead to settling of the bacteria in bottom sediments.[9]
Following findings that the parasite
In 2011, a Eurasian beaver pair was introduced to a beaver project site in West Devon, consisting of a 4.4 acres (1.8 ha) large enclosure with a 600 feet (183 m) long channel and one pond. Within five years, the pair created a complex wetland with an extensive network of channels, 13 ponds and dams. Survey results showed that the created ponds hold 6.50–22.74 pounds per square foot (31.75–111.05 kg/m2) of sediment, which stores 13.19–18.11 long tons; 14.77–20.28 short tons (13.40–18.40 t) of carbon and 0.75–1.04 long tons; 0.84–1.17 short tons (0.76–1.06 t) of nitrogen. Concentrations of carbon and nitrogen were significantly higher in these ponds than farther upstream of this site. These results indicate that the beavers' activity contributes to reducing the effects of soil erosion and pollution in agricultural landscapes.[15]
Effects on animals
Bird abundance and diversity
Beavers help waterfowl by creating increased areas of water, and in northerly latitudes, they thaw areas of open water, allowing an earlier nesting season.[16] In a study of Wyoming streams and rivers, watercourses with beavers had 75-fold more ducks than those without.[17]
Trumpeter swans (Cygnus buccinator) and Canada geese (Branta canadensis) often depend on beaver lodges as nesting sites.[3][18][19] Canada's small trumpeter swan population was observed not to nest on large lakes, preferring instead to nest on the smaller lakes and ponds associated with beaver activity.[20][21]
Beavers may benefit birds frequenting their ponds in several additional ways. Removal of some pondside trees by beavers increases the density and height of the grass–forb–shrub layer, which enhances waterfowl nesting cover adjacent to ponds.[3] Both forest gaps where trees had been felled by beavers and a "gradual edge" described as a complex transition from pond to forest with intermixed grasses, forbs, saplings, and shrubs are strongly associated with greater migratory bird species richness and abundance.[22] Coppicing of waterside willows and cottonwoods by beavers leads to dense shoot production which provides important cover for birds and the insects on which they feed.[23] Widening of the riparian terrace alongside streams is associated with beaver dams and has been shown to increase riparian bird abundance and diversity, an impact that may be especially important in semiarid climates.[24]
As trees are drowned by rising beaver impoundments, they become ideal nesting sites for woodpeckers, which carve cavities that attract many other bird species, including
By perennializing streams in arid deserts, beavers can create habitat which increases abundance and diversity of riparian-dependent species. For example, such as the upper
Bats
Beaver modifications to streams in Poland have been associated with increased bat activity. While overall bat activity was increased,
Trout and salmon
Beaver ponds have been shown to have a beneficial effect on trout and salmon populations. Many authors believe that the decline of salmonid fishes is related to the decline in beaver populations. Research in the Stillaguamish River basin in Washington found that extensive loss of beaver ponds resulted in an 89% reduction in coho salmon (Oncorhynchus kisutch) smolt summer production and an almost equally detrimental 86% reduction in critical winter habitat carrying capacity.[28] This study also found that beaver ponds increased smolt salmon production 80 times more than the placement of large woody debris.[28] Swales and Leving had previously shown on the Coldwater River in British Columbia that off-channel beaver ponds were preferentially populated by coho salmon over other salmonids and provided overwintering protection, protection from high summer snowmelt flows and summer coho rearing habitat.[29] Beaver-impounded tidal pools on the Pacific Northwest's Elwha River delta support three times as many juvenile Chinook salmon (Oncorhynchus tshawytscha) as pools without beaver.[30]
The presence of beaver dams has also been shown to increase either the number of fish, their size, or both, in a study of
Most beaver dams do not pose barriers to trout and salmon migration, although they may be restricted seasonally during periods of low stream flows.
The importance of winter habitat to salmonids afforded by beaver ponds may be especially important in streams without deep pools or where ice cover makes contact with the bottom of shallow streams. Enos Mills wrote in 1913, "One dry winter the stream ... ran low and froze to the bottom, and the only trout in it that survived were those in the deep holes of beaver ponds."[43] Cutthroat trout and bull trout were noted to overwinter in Montana beaver ponds, brook trout congregated in winter in New Brunswick and Wyoming beaver ponds, and coho salmon in Oregon beaver ponds.[41] In 2011, a meta-analysis of studies of beaver impacts on salmonids found that beaver were a net benefit to salmon and trout populations primarily by improving habitat (building ponds) both for rearing and overwintering and that this conclusion was based over half the time on scientific data. In contrast, the most often cited negative impact of beavers on fishes were barriers to migration, although that conclusion was based on scientific data only 22% of the time. They also found that when beaver dams do present barriers, these are generally short-lived, as the dams are overtopped, blown out, or circumvented by storm surges.[37]
By creating additional channel network complexity, including ponds and marshes laterally separated from the main channel, beavers may play a role in the creation and maintenance of fish biodiversity.[44] In off-mainstem channels restored by beaver on the middle section of Utah's Provo River, native fish species persist even when they have been extirpated in the mainstem channel by competition from introduced non-native fish.[45] Efforts to restore salmonid habitat in the western United States have focused primarily on establishing large woody debris in streams to slow flows and create pools for young salmonids. Research in Washington found that the average summer smolt production per beaver dam ranges from 527 to 1,174 fish, whereas the summer smolt production from a pool formed by instream large woody debris is about 6–15 individuals, suggesting that re-establishment of beaver populations would be 80 times more effective.[28]
Beaver have been discovered living in brackish water in estuarine tidal marshes where Chinook salmon (Oncorhynchus tshawytscha) densities were five times higher in beaver ponds than in neighboring areas.[46][47]
Amphibians
A study of mid-elevation (1,840 feet (560 m) - 3,310 feet (1,010 m)) beaver-dammed vs. undammed
Beaver-engineered wetlands in the
Insects
The fallen trees and stripped bark produced by beaver activity provides popular sites for oviposition of the virilis group of Drosophila, including the fruit fly Drosophila montana. Capture of these species of Drosophila for research is significantly more successful near beaver residences. The preference of beavers for birch, willow, and alder corresponds with oviposition site preferences of the Drosophila virilis species group, leading to commensalism between beavers and these species.[53]
Effects on riparian trees and vegetation
Conventional wisdom has held that beavers girdle and fell trees and that they diminish
In a second study of riparian vegetation based on observations of Bridge Creek over a 17-year period, although portions of the study reach were periodically abandoned by beaver following heavy utilization of streamside vegetation, within a few years, dense stands of woody plants of greater diversity occupied a larger portion of the floodplain. Although black cottonwood and thinleaf alder did not generally resprout after beaver cutting, they frequently grew from seeds landing on freshly exposed alluvial deposits subsequent to beaver activity.[57] Therefore, beaver appear to increase riparian vegetation given enough years to aggrade sediments and pond heights sufficiently to create widened, well-watered riparian zones, especially in areas of low summer rainfall. Beavers play an important role in seed dispersal for the water lily populations that they consume.[58]
The surface of beaver ponds is typically at or near bank-full, so even small increases in stream flows cause the pond to overflow its banks. Thus, high stream flows spread water and nutrients beyond the stream banks to wide riparian zones when beaver dams are present.
Finally, beaver ponds may serve as critical firebreaks in fire-prone areas.[59]
Stream restoration
In the 1930s, the U.S. government put 600 beavers to work alongside the Civilian Conservation Corps in projects to stop soil erosion by streams in Oregon, Washington, Wyoming, and Utah. At the time, each beaver, whose initial cost was about $5, completed work worth an estimated $300.[60] In 2014, a review of beaver dams as stream restoration tools proposed that an ecosystem approach using riparian plants and beaver dams could accelerate repair of incised, degraded streams versus physical manipulation of streams.[61]
The province of Alberta published a booklet in 2016 providing information on using beaver for stream restoration.[62]
Utah published a Beaver Management Plan which includes reestablishing beavers in ten streams per year for the purpose of watershed restoration each year from 2010 through 2020.[63]
In a pilot study in Washington, the Lands Council is reintroducing beavers to the upper
In efforts to 'rebeaver' areas of declined beaver populations, artificial logjams have been placed. Beavers may be encouraged to build dams by the creation of a "beaver dam analog (BDA)". Initially, these were made by felling fir logs, pounding them upright into the stream bed, and weaving a lattice of willow sticks through the posts, which beavers would then expand.[69] To minimize labor further, newer postless designs have been used, which in smaller streams, beavers can still expand into sequential dams.[70]
Beaver ponds as wildlife refugia and firebreaks in wildfires
Beaver and their associated ponds and wetlands may be overlooked as effective wildfire-fighting tools.
Urban beavers
Canada
Several Canadian cities have seen a resurgence in its beaver population in recent decades.
Beavers have occasionally wandered into Downtown Ottawa, including Parliament Hill, Major's Hill Park, and Sparks Street.[83] Beavers caught in the urban core of Ottawa by the National Capital Commission's conservation team are typically brought to a wildlife centre, and later released near the Ottawa River, close to the Greenbelt.[83] In 2011, the city of Ottawa began to trap beavers taking up residence in the stormwater pond in the Stittsville neighbourhood.[84] Ottawa is situated 2.5 miles (4 km) south of the southern entrance to Gatineau Park.[85] Located on the Quebec side of the Ottawa River, the park is home to one of North America's densest populations of beavers, with more than 1,100 beavers in 272 beaver colonies according to a 2011 aerial inventory of the park.[85] The beaver population at Gatineau Park is monitored by the National Capital Commission in an effort to protect local infrastructure, and maintain public safety.[85]
The
Several dozen beavers were estimated to inhabit Vancouver in 2016.[81] Beavers have inhabited Jericho Beach as early as 2000, although they did not move into the other areas of Vancouver until later in that decade. After an 80-year absence, a beaver was spotted in Stanley Park's Beaver Lake in 2008.[90] In 2016, five beavers inhabited Beaver Lake.[91] In the same year, a pair of beavers built a dam in Hinge Park.[90] The Vancouver Park Board approved a strategy that included plans to promote the growth of the beaver population near the Olympic Village in 2016.[81]
Beavers in Winnipeg numbered around 100 in 2019, and live along the city's rivers and streams.[92] After receiving complaints for beaver-related damages in 2012, the city of Winnipeg has placed mesh wire fence around tree trunks along the shore of the Assiniboine River during the winter; as well as laid down traps designed to kill the beavers. Like Alberta, provincial guidelines in Manitoba do not allow for the live capture and relocation of beavers.[93] The city employs one contractor 10 times a year to manage the beaver population in Winnipeg, who is authorized to remove beavers with a firearm under Manitoba's Wildlife Act.[92]
United States
Several cities in the United States have seen the reintroduction of beavers within their city limits. In
In downtown
After 200 years, a lone beaver returned to New York City in 2007, making its home along the
In 1999, Washington, D.C.'s annual Cherry Blossom Festival included a family of beavers that lived in the Tidal Basin. The animals were caught and removed, but not before damaging 14 cherry trees, including some of the largest and oldest trees.[110][111][112]
Arctic impacts
As of 2022[update] rapidly increasing temperatures in northern latitudes had resulted in increasingly favorable conditions for beaver as availability of woody vegetation increased and permafrost melted releasing large volumes of water. Increased open water in ponds may increase warming and rapid ecological changes may disrupt fish populations and the harvests of indigenous hunter-gatherers.[113] Increases in beaver and beaver dams interact intimately with thermokarst ponds and lakes. Beavers sometimes build dams at the outlets of thermokarst lakes and in the dried beds of thermokarst depressions as well as in beaded form along streams.[114]
Invasive impacts
In the 1940s, beavers were brought to
See also
References
- S2CID 5940275.
- ^ "Beavers". Regeneration.org. Retrieved March 1, 2022.
- ^ hdl:11250/2438080. Archived from the original(PDF) on March 4, 2012. Retrieved March 1, 2010.
- S2CID 7062322.
- S2CID 84584842. Archived from the original(PDF) on May 13, 2013.
- ^ "Busy Beavers Can Help Ease Drought". Science Daily. February 26, 2008. Retrieved February 23, 2011.
- S2CID 9393979.
- hdl:2148/264.
- S2CID 7397364.
- ^ Gaywood, Martin; Batty, Dave & Galbraith, Colin (2008). "Reintroducing the European Beaver in Britain" (PDF). British Wildlife. Retrieved March 26, 2011.[permanent dead link]
- ISBN 978-0-919813-86-1.
- PMID 2178552.
- PMID 11113253.
- PMID 16725025.
- PMID 30333676.
- .
- S2CID 128410215.
- JSTOR 4082428. Retrieved March 1, 2010.
- ^ Mitchell, C.D. (1994). A. Poole; F. Gill (eds.). Trumpeter Swan (Cygnus buccinator). In The Birds of North America No. 105. Philadelphia: The Academy of Natural Sciences. p. 10.
- JSTOR 40509470. Archived from the original(PDF) on August 8, 2017. Retrieved March 1, 2010.
- ISBN 978-1-55787-067-4.
- S2CID 42955577.
- S2CID 27238489.
- S2CID 62833818.
- S2CID 13053029.
- ^ Johnson, Glenn E. & van Riper III, Charles (2014). "Effects of reintroduced beaver (Castor canadensis) on riparian bird community structure along the upper San Pedro River, southeastern Arizona and northern Sonora, Mexico" (PDF). U.S. Geological Survey Open-File Report 2014-1121. Retrieved January 23, 2015.
- .
- ^ S2CID 27029097. Retrieved February 28, 2010.
- doi:10.1139/f89-032.
- ^ Starre Vartan (August 13, 2019). "Beavers on the coast are helping salmon bounce back. Here's how". National Geographic. Archived from the original on August 13, 2019. Retrieved August 14, 2019.
- ^ S2CID 53405550.
- .
- ^ Rutherford, W.H. (1955). "Wildlife and environmental relationships of beavers in Colorado forests". Journal of Forestry. 53: 803–806. Archived from the original on June 5, 2011. Retrieved February 28, 2010.
- doi:10.1139/f89-213.
- S2CID 85917714.
- ^ a b Pollock, Michael M.; Heim, Morgan & Werner, Danielle (2003). "Hydrologic and geomorphic effects of beaver dams and their influence on fishes" (PDF). American Fisheries Society Symposium. 37: 213–233. Archived from the original (PDF) on July 7, 2011. Retrieved January 17, 2010.
- ^ S2CID 83748069.
- . Retrieved December 23, 2013.
- ^ Bryant, M. D. (1984). Walton, J.M.; Houston, D.B. (eds.). "The Role of Beaver Dams as Coho Salmon Habitat in southeast Alaska Streams". Proceeding, Olympic Wild Fish Conferences. Port Angeles, Washington: Peninsula College, Fisheries Technology program: 183–192.
- ^ Leidholt-Bruner, Karen; Hibbs, David E. & McComb, William C. (1992). "Beaver Dam Locations and Their Effects on Distribution and Abundance of Coho Salmon Fry in Two Coastal Oregon Streams" (PDF). Northwest Science. Archived from the original (PDF) on December 24, 2013. Retrieved April 16, 2011.
- ^ S2CID 8713798.
- S2CID 84441693.
- ISBN 978-0-7661-9387-1.
- S2CID 10070184.
- S2CID 15080970.
- ^ Mapes, Lynda V. (May 18, 2009). "Scientist discovers beavers building prime salmon habitat in Skagit Delta". The Seattle Times. Retrieved June 22, 2010.
- ^ Hood, W. Gregory (2009). "An Overlooked Ecological Web: Sweetgale, Beaver, Salmon, and Large Woody Debris in the Skagit River Tidal Marshes". Skagit River Cooperative. Retrieved June 22, 2010.
- S2CID 230638639.
- S2CID 41445093. Retrieved December 5, 2020.
- ^ Jeff A. Alvarez; Mary A. Shea; Sarah M. Foster (2013). "Rana Draytonii (California Red-legged Frog). Association with Beaver". Herpetological Review. 44 (1): 127–128.
- . Retrieved December 5, 2020.
- . Retrieved December 5, 2020.
- S2CID 83673603.
- S2CID 55147885.
- ^ Benson Ayers, Michael (1997). Aerial Multispectral Videography for Vegetation Mapping and Assessment of Beaver Distribution within Selected Riparian Areas of the Lake Tahoe Basin (Thesis). University of Nevada at Reno. p. 71. Archived from the original on July 20, 2011. Retrieved August 26, 2010.
- S2CID 129844314.
- S2CID 86041868.
- JSTOR 2996604.
- ISBN 978-1-894898-54-6.
- PMID 17840531.
- .
- ISBN 978-0-9688541-6-7. Archived from the original(PDF) on October 4, 2016. Retrieved March 12, 2016.
- ^ Utah Beaver Management Plan (PDF) (Report). Utah Division of Wildlife Resources. January 6, 2010. p. 25. Archived from the original (PDF) on July 22, 2017. Retrieved August 29, 2010.
- ^ Groc, Isabelle (April 19, 2010). "Beavers Sign up to Fight Effects of Climate Change". Discover. Retrieved July 27, 2010.
- ^ "The Beaver Solution: Solving our Water Storage Dilemma in Eastern Washington". The Lands Council. March 2010. Archived from the original on July 4, 2009. Retrieved July 27, 2010.
- ^ "Beavers may be part of answer to climate change". Methow Valley News. January 23, 2016. Retrieved March 12, 2016.
- ^ Ann McCreary (January 24, 2016). "Beavers may be part of answer to climate change". Methow Valley News. Retrieved March 12, 2016.
- ^ Ben Goldfarb (November 9, 2015). "The beaver whisperer". High Country News. Retrieved March 12, 2016.
- ^ Goldfarb, Ben (June 7, 2018). "Beaver dams without beavers? Artificial logjams are a popular but controversial restoration tool". Science | AAAS. Retrieved December 8, 2019.
- ^ "Beaver Dam Analogs". Anabranch Solutions. Retrieved December 8, 2019.
- ^ a b Ben Goldfarb (September 22, 2020). "How beavers became North America's best firefighter". National Geographic. Archived from the original on September 23, 2020. Retrieved September 29, 2020.
- ISBN 978-1-894898-54-6.
- PMID 32881199.
- ^ a b Heather Simmons (December 2, 2015). Beaver reintroduction a watershed success—Busy mammals support clean water, fire protection and climate response (Report). Washington State Department of Ecology. Archived from the original on March 6, 2021. Retrieved September 29, 2020.
- ^ Ralph Maughan (October 25, 2013). "Beaver restoration would reduce wildfires". The Wildlife News. Retrieved September 29, 2020.
- ^ Alexa S. Whipple (2019). Riparian resilience in the face of interacting disturbances: understanding complex interactions between wildfire, erosion, and beaver (Castor canadensis) in grazed dryland riparian systems of low order streams in north central Washington State, USA (Thesis). Eastern Washington University. Retrieved September 29, 2020.
- ^ Erin Stewart (2020). Beavers Buffering Blazes: The Potential Role of Castor canadensis in Mitigating Wildfire Impacts on Stream Ecosystems (PDF) (Thesis). University of Puget Sound. Retrieved September 29, 2020.
- ^ Campbell, Meagan (July 5, 2017). "Canada's beaver problem". Maclean's. Rogers Digital Media. Retrieved July 29, 2019.
- ^ Smith, Kim (June 7, 2016). "'He's quite shy': Beaver sightings on the rise in Calgary". Global News. Corus Entertainment Inc. Retrieved July 29, 2019.
- ^ a b c d Mittelstaedt, Martin (March 5, 2001). "Leave it to beavers, they're loving the big-city life". The Globe and Mail. The Woodbridge Company. Retrieved July 29, 2019.
- ^ a b c d McCutcheon, Andrew (February 2, 2016). "Vancouver's urban-beaver plan focuses on enhancing habitats". The Globe and Mail. The Woodbridge Company. Retrieved July 29, 2019.
- ^ "Beavers". City of Calgary. 2018. Retrieved July 29, 2019.
- ^ a b Douglas, Kayla (May 25, 2019). "Carry on, wayward beaver: Our national animal visits Major's Hill Park". Ottawa Citizen. Postmedia Network Inc. Retrieved July 29, 2019.
- ^ McMahon, Tamsin (November 2, 2011). "City of Ottawa joins fight against the beaver". The National Post. Postmedia Network Inc. Retrieved July 29, 2019.
- ^ a b c Butler, Don (May 20, 2014). "NCC keeping a close eye on Gatineau Park's beaver population". Ottawa Citizen. Postmedia Network Inc. Retrieved July 29, 2019.
- ^ "Featured Mammal: Beaver (Castor canadensis)" (PDF). Mammals of Toronto: A Guide to a remarkable world. City of Toronto. January 2011. p. 32. Retrieved July 29, 2019.
- ^ "Trees in parks & ravines - beavers". 311 Toronto. City of Toronto. 2018. Retrieved July 29, 2019.
- ^ Adler, Mike (December 9, 2013). "Beaver Baffler, invasive species grant help out Rouge Valley watershed". toronto.com. Metroland Media Group. Retrieved August 14, 2019.
- ^ "Annual Local Occurrence Score and Local Rank Update: Terrestrial Fauna and Flora Species, and Vegetation Communities" (PDF). Toronto and Region Conservation Authority. July 2017. Retrieved July 29, 2019.
- ^ a b Judd, Amy (January 4, 2016). "Leave it to beavers: Toothy rodents fell dozens of trees in Vancouver". Global News. Corus Entertainment Inc. Retrieved July 29, 2019.
- ^ "Stanley Park wildlife". City of Vancouver. 2019. Retrieved July 29, 2019.
- ^ a b Scarpelli, Joe (May 30, 2019). "Winnipeg man stunned after beaver shot and killed outside his home". Global News. Corus Entertainment Inc. Retrieved July 29, 2019.
- ^ Glowacki, Laura (July 8, 2018). "Winnipeg should stop killing problem beavers, St. James resident says". CBC News. Canadian Broadcasting Corporation. Retrieved July 29, 2019.
- ^ a b Boehm, Kiersten (November 14, 2008). "Lincoln Park Beaver Relocated". Inside at Your News Chicago, IL Edition. Retrieved December 4, 2009.
- ISBN 978-0-924772-25-2.
- ^ "Park District Kills Beaver in Lincoln Park". MyFoxChicago. April 2009. Retrieved December 4, 2009.
- ^ Greenfield, John (May 7–13, 2009). "Why are there signs that claim the Park District murdered a beaver?". Time Out Chicago. Retrieved December 4, 2009.
- ^ Jones, Carolyn (April 16, 2008). "Moment of truth for Martinez beavers". San Francisco Chronicle.
- ^ "Beavers, water, & the learning curve". martinezbeavers.org.
- ^ George, Aleta (2008). "Martinez Beavers". Bay Nature. Bay Nature Institute. Retrieved November 6, 2009.
- ^ DeRobertis-Theye, Nicola. "Beavers and More in Martinez:New Habitat Thanks to Beavers". Bay Nature. Bay Nature Institute. Retrieved November 6, 2009.
- ^ Farnham, Thomas Jefferson (1857). Life, adventures, and travels in California. Blakeman & Co. p. 383.
- ^ "New York City Beaver Returns". Science Daily. December 20, 2008.
- ^ Miller, Peter (September 2009). "Manhattan Before New York: When Henry Hudson first looked on Manhattan in 1609, what did he see?". National Geographic. Archived from the original on March 17, 2018. Retrieved December 21, 2020.
- ^ O'Connor, Anahad (February 23, 2007). "After 200 Years, a Beaver Is Back in New York City". The New York Times. Retrieved December 4, 2009.
- ^ Trotta, Daniel. "Beaver Returns to New York City After 200 Years." World Environment News. Dec 26, 2007.
- ^ Design Trust for Public Space (June 17, 2009). "Bronx River Crossing". Retrieved December 4, 2009.
- ^ Paddock, Barry (September 19, 2010). "Another beaver makes Bronx River home – doubles total beaver population". Daily News. New York. Retrieved September 19, 2010.
- ^ Newman, Andy (February 7, 2013). "Beaver Gets Busy at Botanical Garden". The New York Times. Retrieved February 13, 2013.
- ^ Aiken, Jonathan (April 7, 1999). "Beaver is bad guy at cherry blossom time". CNN. Retrieved November 22, 2009.
- ^ Wheeler, Linda (April 7, 1999). "Beaver Chomps Into Cherry Blossom Season". The Washington Post. Retrieved November 22, 2009.
- ^ Augenstein, Neal (November 22, 2023). "Eager beavers: Furry buck-toothed visitors have been munching on Tidal Basin's famous cherry trees". WTOP News. Retrieved November 26, 2023.
- ^ David Hasemyer (January 31, 2022). "Beavers Are Flooding the Warming Alaskan Arctic, Threatening Fish, Water and Indigenous Traditions". Inside Climate News. Retrieved February 5, 2022.
- S2CID 216501814.
- ^ hdl:11336/133992. Archived from the original(PDF) on June 5, 2013. Retrieved March 17, 2012.
- ^ Vila, I.; Fuentes, L. S. & Saavedra, M. (1999). "Ictiofauna en los sistema límnicos de la Isla Grande, Tierra del Fuego, Chile" (PDF). Revista Chilena de Historia Natural: 273–284.
- ^ S2CID 55446746.
- ^ Wallem, P. K.; Jones, C. G.; Marquet, P. A. & Jaksic, F. M. (2007). "Identificación de los mecanismo subyacentes a la invasión de Castor canadensis (Kuhl 1820, Rodentia) en el archipiélago de Tierra del Fuego, Chile". Revista Chilena de Historia Natural: 309–325.
- ^ "Argentina eager to rid island of beavers". CNN. Retrieved May 20, 2010.
Bibliography
Goldfarb, Ben (2019). Eager - The Surprising, Secret Life of Beavers and Why They Matter. Chelsea Green Publishing.