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An Unusual Beaver (Castor canadensis) Lodge in a Louisiana Coastal Marsh
Ruth M. Elsey, Steven G. Platt, and Mark Shirley

Southeastern Naturalist, Volume 14, Issue 2 (2015): N28–N30

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2015 Southeastern Naturalist Notes Vol. 14, No. 2 N28 R.M. Elsey, S.G. Platt, and M. Shirley An Unusual Beaver (Castor canadensis) Lodge in a Louisiana Coastal Marsh Ruth M. Elsey1,*, Steven G. Platt2, and Mark Shirley3 Abstract - In Louisiana, Castor canadensis (North American Beaver) rarely occur in coastal marshes and are far more common in forested wetlands. We recently observed a North American Beaver lodge in a coastal marsh that was constructed partly of commercial lumber, possibly made available by recent hurricanes. The animals may have used lumber for lodge construction due to the dearth of trees or other woody vegetation in coastal marshes. This observation points to the adaptability of North American Beaver when choosing materials for lodge construction. Castor canadensis L. (North American Beaver, hereafter Beaver) occupy wetlands throughout much of North America (Novak 1987), and their foraging and dam-building activities can influence ecosystem structure and resource availability in surrounding habitats (Jakes et al. 2007 and references therein). Beavers construct burrows and lodges to provide shelter, assist in thermoregulation, and avoid predators; dams also enhance habitat by raising water levels (Rosell et al. 2005, Zurowski 1992). Novak (1987) reviewed the environmental impacts caused by Beavers and their activity, including benefits—stabilization of stream flow, raising pond-water temperature, and promoting silt deposition leading to an increase in plankton and invertebrates—and adverse effects—interrupting trout migration, flooding spawning areas, and providing favorable conditions for predators and parasites. Beavers are considered ecosystem engineers whose activity can increase habitat heterogeneity and diversity of herbaceous plant species (Wright et al. 2002), and Beaver dam-building activity can be important in creating favorable riparian conditions (pond and wetland habitat) for a rich and abundant bird community (Cooke and Zack 2008). Beaver lodges have been found to be important in structuring littoral communities in boreal headwater lakes (France 1997). Dams and lodges are typically constructed of logs, sticks, mud, and stones (Jung and Staniforth 2010, Novak 1987 and references therein), and the building behavior of Beaver is summarized by Novak (1987). Other studies list the materials typically used for lodges as mud and debarked tree stems and limbs; lesser amounts of other woody and herbaceous vegetation may also be used (Rue 1964, as cited in Allen 1983). Platt et al. (2009) reported a site in South Dakota where Beavers used Typha sp. (cattails) to construct dams when woody vegetation was absent. Jung and Staniforth (2010) described 2 dams made primarily of medium-sized rocks because mining activities had removed much of the original forest. Below we describe a Beaver lodge in a Louisiana coastal marsh that was also built with unusual materials. Beavers occur throughout Louisiana, but are more common in the Florida parishes of southeast Louisiana (Chabreck 1958, Lowery 1974); they have extended their range into the central coastal parishes of Louisiana (Ensminger and Linscombe 1982) including coastal southwestern Louisiana (Elsey and Kinler 1996). Unlike in forested wetlands where Beavers most commonly occur in Louisiana, coastal marshes contain few trees and are 1Louisiana Department of Wildlife and Fisheries, 5476 Grand Chenier Highway, Grand Chenier, LA 70643. 2Wildlife Conservation Society, Myanmar Program, Aye Yeik Mon 1st Street, Yadanamon Hosuing Avenue, Yangon, Myanmar. 3Aquaculture and Coastal Resources, Louisiana State University, AgCenter Southwest Region, Louisiana Sea Grant College Program, 1105 W. Port Street, Abbeville, LA 70510. *Corresponding author - relsey@wlf.la.gov. Manuscript Editor: Andrew Edelman Notes of the Southeastern Naturalist, Issue 14/2, 2015 N29 2015 Southeastern Naturalist Notes Vol. 14, No. 2 R.M. Elsey, S.G. Platt, and M. Shirley likely marginal habitat for Beavers. Indeed, Chabreck (1958) documented 1 Beaver colony in a small inland marsh containing 2 lodges and a dam; he noted that the dam was built of mud and marsh plants but contained practically no wood. Lowery (1974) summarized prior studies of the woody plants used by Beavers in Louisiana, both for food items and for building materials. He cited Noble (1958) who found that the most frequently utilized woody plants were Pinus taeda L. (Loblolly Pine), Liquidambar sp. (sweetgum), Halesia sp. (silverbell), and Magnolia virginiana L. (Sweetbay), among others. During a helicopter survey to locate Alligator mississippiensis Daudin (American Alligator) nests, we observed a Beaver lodge in coastal marsh (29o47'59.1471''N, 92o3'58.8254''W) approximately 7.7 km east of Intracoastal City, LA. Initially, it appeared to be an unusually large mound of vegetation, and we were uncertain as to whether it was an American Alligator nest or possibly an Ondatra zibethucus L. (Common Muskrat) house, which would be similar in appearance. On 21 June 2011, M. Shirley was checking the location to determine if it was an American Alligator nest, and noted that it was a Beaver lodge in an intermediate marsh habitat (Fig. 1). Interestingly, it was constructed mostly of mud and marsh vegetation, but also contained several pieces of what appeared to be commercial lumber (1 plywood plank and two 2” × 2” boards). The vegetation used was from the marsh immediately surrounding the lodge and included Spartina patens (Aiton) Muhl. (Salt Marsh Hay) and Phragmities australis Roth (Common Reed). He also observed 1 girdled, felled tree limb in the lodge, but saw no Beavers; the lodge was approximately 4 m in diameter and 1.3 m high. Due to severe hurricanes in the region (Hurricane Rita in 2005 and Hurricane Ike in 2008), debris from damaged anthropogenic structures may have been readily available for Figure 1. Castor canadensis (North American Beaver) lodge constructed partially of commercial lumber and containing minimal tree limbs in a coastal Louisiana marsh. 2015 Southeastern Naturalist Notes Vol. 14, No. 2 N30 R.M. Elsey, S.G. Platt, and M. Shirley use by Beavers in constructing their lodges. Also, it is possible the commercial lumber floated onto the lodge due to high water and strong storm tides and localized flooding in June 2011 rather than being carried there by the Beaver; however, the boards appeared to be incorporated within the lodge and not resting atop the lodge, as they may have been had they floated into place. There was natural vegetative material at the apex of the lodge, and the lumber pieces appeared to be just below that, within the lodge interior. This observation is unusual for 2 reasons: first, Beavers are uncommon and scattered in coastal Louisiana marshes, and it provides further evidence of their extension into these habitats. Moreover, some of the materials used for construction of this lodge are atypical and of anthropogenic origin, possibly due to the paucity of trees and woody vegetation in the marsh environment. The Beavers’ adaptability and resiliency in using locally available non-typical materials for lodge construction is apparent, and is similar to findings reported by others (Jung and Staniforth, 2010, Platt et al. 2009) where typical materials were limited or absent for dam and lodge construction. Acknowledgments. We thank Dr. Andrew Edelman and 2 anonymous reviewers for assistance with improvements to the manuscript. We also appreciate the initial observation made by Mr. Mike Breaux while piloting the helicopter during searches for American Alligator nests. Literature Cited Allen, A.W. 1983. Habitat-suitability index models: Beaver. US Fish and Wildlife Service. FWS/ OBS-82/10.30 revised. US Department of the Interior, Washington, DC. 20 pp. Chabreck, R.H. 1958. Beaver–forest relationships in St. Tammany Parish, Louisiana. Journal of Wildlife Management 22:179–183. Cooke, H.A., and S. Zack. 2008. Influence of Beaver dam density on riparian areas and riparian birds in shrubsteppe of Wyoming. Western North American Naturalist 68:365–373. Elsey, R.M., and N. Kinler. 1996. Range extension of the American Beaver, Castor canadensis, in Louisiana. Southwestern Naturalist 41:91–93. Ensminger, A., and G. Linscombe. 1982. The fur animals, the Alligator, and the fur industry in Louisiana. Louisiana Department of Wildlife and Fisheries, Wildlife Education Bulletin 109:1–70. France, R.L. 1997. The importance of Beaver lodges in structuring littoral communities in boreal headwater lakes. Canadian Journal of Zoology 75:1009–1013. Jakes, A.F., J.W. Snodgrass, and J. Burger. 2007. Castor canadensis (Beaver) impoundment associated with geomorphology of Southeastern streams. Southeastern Naturalist 6:271–282. Jung, T., and J.A. Staniforth. 2010. Unusual Beaver, Castor canadensis, dams in central Yukon. The Canadian Field-Naturalist 124:274–275. Lowery, G.H., Jr. 1974. The Mammals of Louisiana and its Adjacent Waters. Kingsport Press, Inc. Kingsport, TN. 565 pp. Noble, R.E. 1958. The survival, adaptation, distribution, and ecology of transplanted Beaver (Castor canadensis) in Louisiana. M.Sc. Thesis. Louisiana State University, Baton Rouge, LA. 215 pp. Novak, M. 1987. Beaver. Pp. 280–312, In M. Novak, J.A. Barber, M.O. Obbard, and B. Mallach (Eds.). Wild Furbearer Management and Conservation in North America. Published by the Ontario Trappers Association under the authority of the Licensing Agreement with the Ontario Ministry of Natural Resources, Peterborough, ON, Canada. 1150 pp. Platt, S.G., Z.F. Horse, T.R. Rainwater, and S.M. Miller. 2009. Distribution records and comments on mammals in Western South Dakota. Western North American Naturalist 69:329–334. Rosell, F., O. Bozser, P. Collen, and H. Parker. 2005. Ecological impact of Beavers Castor fiber and Castor canadensis and their ability to modify ecosystems. Mammal Review 35:248–276. Rue, L.E. III. 1964. The World of the Beaver. J.B. Lippencott Co., Philadelphia, PA. 155 pp. Wright, J.P., C.G. Jones, and A.S. Flecker. 2002. An ecosystem engineer, the Beaver, increases species richness at the landscape scale. Oecologia 132:96–101. Zurowski, W. 1992. Building activity of Beavers. Acta Theriologica 37:403–411.