Wednesday, November 19, 2008

Damming Beavers!

According to the South Carolina Department of Natural Resources (SCDNR) webpage, The beaver, the largest rodent found in North America, was once abundant in South Carolina, and was found commonly in all areas with the exception of a narrow strip of sandy soil along the coast. These animals were trapped extensively by early trappers and by the late 1800s or early 1900s had disappeared from most of the state. Many feel the beaver was eradicated; however, some remnant populations may have persisted in remote areas.

During the winter of 1940 to 1941, United States Fish and Wildlife Service personnel released six beavers, which were captured in Georgia, on the Sandhills Wildlife Refuge in Chesterfield County, South Carolina. During the same period, beavers from Georgia began to invade the Savannah River drainage system. These animals established populations in counties which border the Savannah River.

The beavers in these two areas and existing remnant populations have increased their range significantly and presently occur in portions of all 46 counties in the state.

Several years ago, beavers returned to area near the boardwalk at Beidler Forest and we've since noted their activity in previous entries (1, 2). However, except for a pathetic attempt at a lodge off of Mallard Lake, we have not seen any damming within our 1.5-mile wide swamp. Damming within the swamp is certainly possible (although we thought improbable) as South Carolinians named an entire swamp for that activity. Beaver Dam Swamp is located east of Lake Moultrie near the intersection of SC 45 and US 17-A (Decimal Degrees: Latitude: 33.29833 Longitude: -79.78528). Maybe the beavers we discovered during our off-boardwalk exploration received their training in Beaver Dam Swamp.

As we walked back to the nature center on a path between the boardwalk and the cross-swamp powerline, we discovered a beaver dam across one of the many channels in the swamp. This particular channel flows under the boardwalk at #5. In the satellite image, you can see the channel of water as it crosses the clearing under the powerline. The dam is built along the southern edge of the powerline clearing and is stitched between the buttresses of trees, root masses, fallen logs, stumps, and finally to higher 100 meters to the east. The lodge is located in the deep water near the center of the powerline clearing (it appeared as if it would top our hip waders on a day that didn't top 40F, so we didn't obtain a more accurate depth reading).

Although rising water will likely overtop the dam or simply spill around the current east and west anchor points, the water currently pooled behind the dam will be irresistible to wintering waterfowl! Besides humans, no animal has the power to so dramatically alter its environment. Beavers may abandon the site when rising water circumvents their engineering project, but they will undoubtedly attempt to first modify their dam to contain the water in its new configuration.

Images by Mark Musselman

No comments: