Abstract
Many mammalian species have considerable influences on their ecosystems. In the Norwegian boreal forest landscape, two animals with a significant impact on the environment are moose (Alces alces) and the Eurasian beaver (Castor fiber), who often share similar ecosystems and may compete for the same resources. Nevertheless, the correlations between these two species and habitat composition remain underexplored. We hypothesized that exploitative competition exists between beavers and moose, which would be expressed as a change in their foraging patterns in areas with high moose densities compared to low moose densities.
At a local scale, we monitored available woody vegetation and woody stems cut by beaver foraging at 17 different lodges. For each stem, information on the tree species, the tree size and the distance from the shoreline was noted. We analyzed the probability of a stem being cut by beavers in relation to the distance from the shore, the tree species, and the tree size in areas with high and low moose densities.
The results indicated a negative correlation between the proportion of cut stems, depending on tree species, tree size and distance from the shore, and summer moose densities. The predicted proportion of cut stems was generally higher in areas of low summer moose densities. This was especially the case for small cut stems, birch trees and stems close to the shore, but a similar trend could be seen for large stems, willow trees and stems further from the shore. No correlation was identified between winter moose densities and the predicted proportion of cut stems.
The findings of this study indicate that exploitative competition occurs between beavers and moose during the summer season. Nevertheless, it remains unclear whether exploitative competition can fully account for the observed results. The findings indicate a need for further research to gain a comprehensive understanding of the complex relationships between beavers, moose, and their ecosystem.
Keywords: Alces alces, boreal forest, Castor fiber, ecosystem engineer, Eurasian beaver, exploitative competition, herbivory, moose, Norway
