Fig 1.
Location of the Chequamegon-Nicolet National Forest and the northern Wisconsin stream network.
Streams surveyed during fall for active beaver colonies on the Chequamegon-Nicolet National Forest. Targeted streams are in magenta and non-targeted streams are in green. The grey background for the stream network is the topography of northern Wisconsin as represented by a hillshade model. Weather data were obtained from the indicated National Weather Service Cooperative Observer Program (COOP) weather stations.
Table 1.
Effort for aerial surveys of beaver colonies made October–November along four categories of streams in the Chequamegon-Nicolet National Forest, 1987–2013 (Nicolet side) and 1997–2013 (Chequamegon side).
Targeted streams were subject to the beaver control program.
Table 2.
Variables used to assess the ability of weather to explain minor variations in the beaver density index on non-managed streams or function as drivers of trends on those streams.
Each variable was computed for the current year and the three preceding years. Variables were standardized against their long-term averages (1983–2013).
Fig 2.
Beaver colony numbers/km by year for (a) trout streams without targeted beaver management and (b) trout streams with targeted beaver management for the Chequamegon-Nicolet National Forest.
In panel (a), open circle = Nicolet trout streams, filled circle = Nicolet non-trout streams, open square = Chequamegon trout streams, filled square = Chequamegon non-trout streams. In panel (b), open circle = Nicolet side, triangle = Chequamegon side. Dotted lines are the predicted trends from generalized additive models (significant trends only).
Table 3.
Weather models for beaver colony density on streams where no targeted beaver management occurred on the Chequamegon side of the Chequamegon-Nicolet National Forest, 1997–2013.
Models listed are the minimum AIC model, competitive models (those models within 2 AC units of the 006Dinimum), and the 2007 drought model. The evidence ratio is the ratio of the Akaike weights for the minimum AIC model and an alternate model.
Table 4.
Time trend and weather models for beaver colony density on streams where no targeted beaver management occurred on the Nicolet side of the Chequamegon-Nicolet National Forest, 1987–2013.
Models listed are the minimum AIC model, competitive models (those models within 2 AC units of the minimum), and the trend model.