Foraging decisions with conservation consequences: Interaction between beavers and invasive tree species.

Area of Science:

• Ecology
• Invasive Species Biology
• Conservation Biology

Background:

• Herbivore foraging selectivity influences plant community dynamics, affecting native and invasive species.
• Beaver (Castor spp.) populations are increasing, yet their interactions with invasive woody plants are understudied.
• Understanding these interactions is crucial for predicting and managing woody plant invasions in riparian ecosystems.

Purpose of the Study:

• To investigate beaver foraging decisions regarding native and invasive woody plants.
• To analyze the influence of plant taxon, diameter, and distance from water on beaver utilization.
• To assess the impact of beaver herbivory on the composition and structure of floodplain vegetation.

Main Methods:

• Field data collected at 20 sites in Hungary, recording woody plant taxon, diameter, utilization type, and distance from water.
• Statistical analysis using a dual approach (whole-database and transect-level) to examine beaver foraging strategy.
• Quantification of 5401 woody units (trunks and thick branches) to determine utilization patterns.

Main Results:

• Beaver foraging selectivity was significantly influenced by plant taxon, diameter, and distance from water.
• Preferred taxa included softwoods (Populus, Salix) over invasive hardwoods (Fraxinus pennsylvanica, Acer negundo).
• Larger diameter trees were carved/debarked rather than felled, while invasive species were primarily utilized in the smallest diameter class, potentially leading to softwood loss and favoring invasive hardwoods.

Conclusions:

• Beaver herbivory accelerates the shift towards invasive hardwood species in riparian canopies, supporting the enemy release hypothesis.
• Selective foraging on native softwoods may lead to their gradual loss or shrubby transformation.
• Long-term impacts depend on plant regeneration and response to utilization; integrating these findings with species competitiveness is vital for floodplain conservation.