Authors: Juhász, Erika; Vági, Balázs;Molnár, Zsolt;Sári, Gergő;Szabó, Gyula;Klébert, Antal;Katona, Krisztián;Németh, András;Biró, Marianna;

Wetlands are exposed to several threats, e.g., the loss of habitat complexity, decreasing water levels and biological invasion. Beavers, as ecosystem engineers, are able to influence these processes. We studied the selective foraging of beavers at 20 sites along the Danube and its tributaries. Additionally, 10 further beaver-altered habitats were surveyed to understand the effects of beaver dams on amphibian and reptile species richness. We counted amphibian and reptile individuals along transects and registered egg clutches and larvae of amphibians to assess the reproductive success of each species. We also involved the 5 largest beaver-reconstructed wetlands in bird monitoring surveys. Based on our results, beavers generally preferred native woody species against invasive ones, which may indirectly accelerate the process of the biological invasion. However, dam-building created habitat for several studied native vertebrate taxa: Nine amphibian species used the beaver meadows and ponds as breeding sites and migratory waterfowl used them as a stop-over site. Our study supports that, by the rapid reoccupation of aquatic habitats in their former range, beavers might become a driver of landscape change across Europe. Therefore, understanding their effects on the environment will have critical importance in conservation planning and freshwater habitat management.