Freshly felled, rapidly used: Beaver-felled trees as immediate resources for mammals and birds

Beavers (Castor spp.), as ecosystem engineers, increase structural complexity and biodiversity in riparian forests through dam-building and tree-felling activities. However, the role of freshly felled trees as terrestrial resources for wildlife remains underexplored. We conducted a camera trap study in the riparian forests of northern Poland, monitoring 32 freshly felled trees across 12 beaver territories, and eight tree species over two consecutive autumn-winter seasons (2021-2023). Camera traps operated continuously, recording animal activity and interactions with logs. Each vertebrate observed was categorized by its position relative to the log and by behavioral type, with direct use defined as any interaction with a felled trunk (e.g., walking, climbing, perching). Of the 50 taxa recorded, 44 (88%) were observed using the logs, with small mammals and mesocarnivores as the most frequent users. Active use-including movement, perching, scent-marking, and foraging-accounted for 68% of all behaviors. The taxonomic composition of birds and mammals differed significantly between utilization and non-utilization records, with variation driven by tree-specific microhabitat features and species-specific behaviors. Martens, mice, red foxes, and several bird taxa (e.g., Northern wrens, great tits) showed strong preferences for the felled trees, while large herbivores and some mustelids avoided them. The broad range of observed behaviors suggests that felled logs serve multiple ecological functions and facilitate species coexistence. Temporal partitioning was strongest between diurnal birds and predominantly nocturnal mammals; red foxes were the most temporally distinct, whereas beavers, mice, and martens showed greater overlap in diel activity. First-detection sequences indicated rapid uptake, with red foxes and mice typically among the earliest taxa recorded at newly felled trees, whereas species such as jays and badgers tended to appear later within each tree's monitoring window. Our findings demonstrate that beaver-felled trees function as ecological hotspots, rapidly increasing resource heterogeneity and connectivity in managed riparian forests. These results highlight the conservation value of beaver-driven structural complexity for supporting biodiversity and ecosystem function. Recognizing and retaining beaver-felled logs and similar deadwood structures should be a priority in forest management and restoration to maintain diverse and multifunctional wildlife communities.