Riparian zones are a conservation concern because of their many ecosystem functions. The North American beaver is a keystone riparian obligate which creates and maintains riparian areas by building dams. In many parts of the eastern U.S. invasive shrubs are common in riparian zones, but we do not know if beavers promote or inhibit these invasions. We investigated whether beavers use the invasive, Amur honeysuckle (Lonicera maackii), preferentially compared to other woody species. At each of eight sites in southwestern Ohio, we identified woody stems > 2.5 cm diameter on two 120x2 meter transects parallel to the water’s edge and six, 25 meter secondary transects perpendicular to these, recording for each stem diameter, distance the woody stem is to the water’s edge, and whether the stem was cut by beaver. To determine the role of species and other factors in determining cutting by beaver, we conducted binomial generalized regressions, using distance from the water’s edge, diameter, and species as fixed factors and site and transect nested within site as random factors. To quantify beaver preference, we calculated Vanderploeg and Scavia’s electivity index (Ei) for each genus at each site utilizing the proportion of stems cut compared to available stems.
Results/Conclusions
Lonicera maackii was the most common woody species at six of the eight sites and comprised 41% (range 0-75%) of the total cut stems. However, L. maackii tended to be avoided (Ei < 0) at six sites, and only preferentially cut (Ei > 0) at two. The other common invasive shrub in the study sites, Autumn Olive (Elaeagnus umbellatea), was preferentially cut at five of the six sites where it was common. Box Elder (Acer negundo) was preferentially cut at all eight study sites. We could not distinguish between beaver use of cut stems for food or construction. Overall, beavers did not preferentially cut L. maackii despite the fact that this invasive shrub comprised a large proportion of the total cut stems within most study sites. Further analysis will reveal the importance of stem diameter and distance from the water’s edge on beaver selection.