Central Place Foraging by Beavers (Castor canadensis) in a Complex Lake Habitat

Patterns in Beaver Herbivory in South-Central Kansas Riparian Woodlands

“…Raffel et al (2009) showed that, for beaver colonies in an Ohio reservoir, the distance through the water from the lodge to trees had a much weaker, although statistically significant, effect than distance from the shore to trees in explaining beaver foraging preferences even though distances through water were 10X greater than the distances traveled on land.…”

“…When a tree had been "cut," we estimated dbh from basal diameter. Because Raffel et al (2009) found a quadratic relationship between stem diameter and probability of being "cut," we used deviance values to evaluate the fit of a logistic regression model for girdling probability in which the independent variable was dbh vs. fit of a logistic regression model that included both dbh and dbh 2 as independent variables. Lower deviance values indicate better fit.…”

“…Distance traveled through water may have less impact on beaver foraging decisions than distance traveled on land because predation risk for beavers in water is less (Basey and Jenkins 1995) and buoyancy provided by water is hypothesized to reduce the energetic costs of carrying food (Raffel et al 2009). Raffel et al (2009) showed that, for beaver colonies in an Ohio reservoir, the distance through the water from the lodge to trees had a much weaker, although statistically significant, effect than distance from the shore to trees in explaining beaver foraging preferences even though distances through water were 10X greater than the distances traveled on land.…”

“…Specifically, theory predicts that central place foragers will become increasingly selective in their choice of food items at longer distances from the home base (Schoener 1979, Orians andPearson 1979). Beavers often narrow the range of stem diameters (Jenkins 1980, Pinkowski 1983, Haarberg and Rosell 2006, Raffel et al 2009) and, in some ecosystems, narrow the range of tree species (Pinkowski 1983, Raffel et al 2009) that they cut (meaning "girdle, fell and remove the stem") at longer distances from water. Therefore, not only the magnitude, but also the direction of beavers' effects on the riparian plant community may vary with distance from the stream.…”

“…Because canopy trees in many riparian woodlands may have recruited during periods when beavers were rare, renewed species-specific gnawing damage may cause changes to the current composition of these woodlands. While ecologists have explored the impacts of beavers on tree species composition near lakes or rivers in boreal (Belovsky 1984, Donkor andFryxell 2000), montane (McGinley and Whitham 1985) and eastern deciduous forest (Jenkins 1980, Raffel et al 2009) regions of North America, little research has addressed the role of beaver herbivory in affecting riparian community composition on the central or southern Great Plains. In Great Plains ecosystems, where cropland and grassland are the predominant land cover types, riparian woodlands add habitat complexity and enhance biodiversity (Magill, Smith andRay 2003, Hall et al 2006).…”