Time-dependent effects of beavers on terrestrial invertebrate biomass and diversity

Beaver (Castor spp.) activity can alter habitat structure and hydrology, yet their influence on terrestrial invertebrates remains understudied. We examined the effects of beaver activity on ground-dwelling terrestrial invertebrate biomass and diversity across mid-summer to early autumn and assessed habitat differences between sites with and without beaver activity by analyzing environmental variables related to habitat heterogeneity. We found significant interactions between beaver activity and research dates, suggesting that beaver effects are dynamic and seasonally dependent. Specific invertebrate orders and Coleoptera families were significantly associated with beaver-active sites, indicating that beaver-modified habitats support distinct invertebrate assemblages. Habitat heterogeneity, measured as the normalized difference vegetation index (NDVI), also varied temporally, with a significant interaction between beaver activity and date. These results demonstrate that beavers can enhance invertebrate biodiversity, partly through increasing habitat heterogeneity, and highlight the importance of sampling timing when evaluating how rewilding and keystone species reintroductions affect invertebrate communities.