Beavers in the Sierra Nevada

The North American beaver (Castor canadensis) had a historic range that overlapped the Sierra Nevada in California. Before the European colonization of the Americas, beaver were distributed from the arctic tundra to the deserts of northern Mexico.[1] The California Golden beaver subspecies (Castor canadensis subauratus) was prevalent in the Sacramento and San Joaquin River watersheds, including their tributaries in the Sierra Nevada. Recent evidence indicates that beaver were native to the High Sierra until their extirpation in the nineteenth century.

A beaver lodge in McGee Creek, eastern Sierra Nevada, California.

Historical range and distribution
A conifer felled by beaver on Meeks Creek, Lake Tahoe August, 2010

In 1916, Harold Bryant wrote in California Fish and Game, "The beaver of our mountain districts has been entirely exterminated and there are but a few hundred survivors to be found along the Sacramento, Colorado and San Joaquin Rivers."[2] Earlier, in 1906, Frank Stephens wrote in "California Mammals" that Castor canadensis' historic range was from the "Pacific slope from Alaska to central California east to and including the Sierra Nevada and Cascade Mountains" and adds "In most parts of California the presence of beavers is only made known by the stumps of the trees and saplings that they have cut."[3] McIntyre hypothesized that beaver were trapped out of the Sierra early in the nineteenth century by trappers before records could be kept.[4] Other early twentieth century naturalists (Grinnell, Tappe, etc.) questioned whether the California Golden beaver dwelt above 1,000 feet (300 m) of elevation in the Sierra.[5][6] In 2012, physical evidence demonstrated that beaver were native to the Sierra until at least the mid-nineteenth century, via radiocarbon dating of buried beaver dam wood uncovered by deep channel incision in two locations in Red Clover Creek in the Feather River watershed.[7] That report was supported by a summary of indirect evidence of beaver including reliable observer accounts of beaver in multiple watersheds from the northern to the southern Sierra Nevada, including its eastern slope.[8]

Reintroduction to the Sierra
North American beaver on the bank of the Lower Kern River

California Golden beaver taken from Snelling, California (elevation 256 ft or 78 m and Waterford, California (elevation 51 ft or 16 m) were stocked in 1940 at Mather Station (elevation 4,522 ft or 1,378 m) west of Yosemite National Park and in 1944 at Fish Camp (elevation 5,062 ft or 1,543 m) by the California Department of Fish and Game (CDFG). These native "Central Valley" beaver have been building dams and rearing young successfully for 70 years in and near Yosemite at elevations higher than 5,000 feet (1,500 m).[4] A second reference confirms that the CDFG re-introductions of beaver into Mariposa County in the Merced River watershed were all C. C. subauratus (Golden beaver) taken from near sea level elevations.[9] These lowland beaver adapted to the high Sierra without difficulty.

Castor canadensis were re-introduced to the Tahoe Basin by the CDFG and the U. S. Forest Service between 1934 and 1949 in order to prevent stream degradation and to promote wetland restoration. Descended from no more than nine individuals from the Snake River in Idaho, 1987 beaver populations on the upper and lower Truckee River had reached a density of 0.72 colonies (3.5 beavers) per kilometer.[10]

Ecology
A beaver dam on Meeks Creek, Lake Tahoe August, 2010

Recently beaver have been documented in the upper and lower Truckee River, Ward Creek, Cold Creek, Taylor Creek, Meeks Creek, Blackwood Creek, and King's Beach, so the descendants of the original nine beavers have apparently migrated around most of Lake Tahoe.[11][12][13] A 2007 study of Taylor Creek showed that the beaver dam removal decreased wetland habitat, increased stream flow, and increased total phosphorus pollutants entering Lake Tahoe - all factors which negatively impact the clarity of the lake's water.[14] In addition, beaver dams located in Ward Creek, located on the west shore of Lake Tahoe, were also shown to decrease nutrients and sediments traveling downstream.[14]

Effects on aspen, cottonwood and willow

In 1987, Beier reported that beaver had caused local extinction of Quaking aspen (Populus tremuloides) and Black cottonwood (Populus trichocarpa) on 4-5% of stream reaches on the lower Truckee River, however Willow (Salix spp.) showed good vigor despite heavy use in most reaches. He further speculated that without control of beaver populations that aspen and cottonwood could go extinct on the Truckee River.[15] However, not only have aspen and cottonwood survived ongoing beaver colonization but a recent study of ten Tahoe streams utilizing aerial multispectral videography has shown that deciduous, thick herbaceous, and thin herbaceous vegetation are more highly concentrated near beaver dams, whereas coniferous trees are decreased.[11]

Effects on salmonids

Until recently, beaver were considered pests who caused flooding and impaired the passage of spawning trout and salmon. However, it has been shown that trout and salmon move freely across beaver dams.[16] The presence of beaver dams has also been shown to either increase the number of fish, their size, or both, in a study of brook, rainbow and brown trout in Sagehen Creek, which flows into the Little Truckee River at an altitude of 5,800 feet (1,800 m).[17]

Current control methods

As of 2023, the California Department of Fish and Game recognizes the ecosystem services provided by beavers across the state.[18] In cases where beavers are harming human property, the DFG will first attempt to educate the human party, and only then issue a limited permit to kill the beaver.[18]

See also

References
  1. Naiman, Robert J.; Johnston, Carol A.; Kelley, James C. (Dec 1988). "Alteration of North American Streams by Beaver" (PDF). BioScience. 38 (11): 753–762. doi:10.2307/1310784. JSTOR 1310784. Archived from the original (PDF) on 2012-03-04. Retrieved Feb 28, 2010.
  2. Bryant, H.C. (1915). California's fur-bearing mammals. San Francisco, California: State of California, Resources Agency, Dept. of Fish and Game. p. 96. Retrieved Mar 17, 2010.
  3. Stephens, Frank (1906). California Mammals in West Coast Nature Series. San Diego, California: The West Coast Publishing Company. p. 97. Retrieved 2010-06-19.
  4. McIntyre, Robert N. (April 1948). "A New Park Resident" (PDF). Yosemite Nature Notes. Retrieved Jan 23, 2010.
  5. Grinnell, Joseph; Dixon, Joseph S.; Linsdale, Jean M. (1937). Fur-Bearing Mammals of California: Their Natural History, Systematic Status and Relations to Man. Berkeley, California: University of California Press. p. 636. ISBN 978-0-7812-5041-2.
  6. Tappe, Donald T. (1942). "The Status of Beavers in California" (PDF). Game Bulletin No. 3. California Department of Fish & Game. Archived from the original (PDF) on July 27, 2011. Retrieved Apr 11, 2010.
  7. James, C.D.; Lanman, R.B. (Spring 2012). "Novel physical evidence that beaver historically were native to the Sierra Nevada" (PDF). California Fish and Game. 98 (2): 129–132.
  8. Lanman, RB; Perryman, H; Dolman, B; James, CD (Spring 2012). "The historical range of beaver in the Sierra Nevada: a review of the evidence" (PDF). California Fish and Game. 98 (2): 65–80.
  9. Hensley, Arthur L. (1946). "A Progress Report on Beaver Management in California". California Fish and Game. 32 (2): 87–99. Retrieved Mar 26, 2010.
  10. Beier, Paul; Barrett, Reginald H (1989). "Beaver Distribution in the Truckee River Basin, California" (PDF). California Fish and Game. Archived from the original (PDF) on 2011-07-20. Retrieved Jan 17, 2010.
  11. Ayers, Michael Benson (October 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. Retrieved 2010-08-26.
  12. "The Beavers of the Truckee River". Tahoe Arts and Mountain Culture. July 20, 2009. Archived from the original on 2011-06-09. Retrieved Jan 19, 2010.
  13. Van Lom, Keaven (Jan 16, 2010). "This is Wildlife Management in the 21st Century?". Moonshine Ink. Archived from the original on 2012-03-03. Retrieved Jan 17, 2010.
  14. Muskopf, Sarah (October 2007). The Effect of Beaver (Castor canadensis) Dam Removal on Total Phosphorus Concentration in Taylor Creek and Wetland, South Lake Tahoe, California (PDF) (Thesis). Humboldt State University, Natural Resources. hdl:2148/264.
  15. Beier, Paul; Barrett, Reginald H. (October 1987). "Beaver Habitat Use and Impact in Truckee River Basin, California". Journal of Wildlife Management. 51 (4): 794–799. doi:10.2307/3801743. JSTOR 3801743.
  16. 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 2011-07-07. Retrieved Jan 17, 2010.
  17. Gard, R (1961). "Effects of beaver on trout in Sagehen Creek, California". Journal of Wildlife Management. 25 (3): 221–242. doi:10.2307/3797848. JSTOR 3797848.
  18. "Beaver Depredation Policy in California". California Department of Fish and Wildlife. June 5, 2023. Departmental Bulletin 2023-02.
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