North American beaver (Castor canadensis) were re-introduced to the Tahoe Basin by the California Department of Fish and Wildlife and the U.S. Forest Service between 1934 and 1949. Descended from no more than nine individuals, 1987 beaver populations on the upper and lower Truckee River had reached a density of 0.72 colonies (3.5 beavers) per kilometer.[37] At the present time beaver have been seen in Tahoe Keys, Taylor Creek, Meeks Creek at Meeks Bay on the western shore, and Kings Beach on the north shore, so the descendants of the original nine beavers have apparently migrated around most of Lake Tahoe.[38][39] Recently novel physical evidence has 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 the Feather River watershed.[40] 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.[41] A specific documented record of beaver living historically in Lake Tahoe's North Canyon Creek watershed above Glenbrook includes a description of Spooner Meadow rancher Charles Fulstone hiring a caretaker to control the beaver population in the early 20th century.[42] A recent study of Taylor Creek showed that 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.[43] 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.[43]