IMPACT ASSESMENT OF BEAVER REINTRODUCTION ON AMPHIBIANS OF SMALL RIVERS
Study of impact assessment of beaver reintroduction in valleys of small rivers on amphibians was carried out. The work took place on the territories of the state nature reserves: Rdeyskiy, Prioksko-Terrasny and Privolzhskaya Lesostep. Small rivers of the area under study have been inhabited by beavers in different years, so degree of beavers’ impact on valley ecosystems differed. This fact allowed us to study amphibians in different conditions. The main factors of beavers’ impact on amphibians were modifications of lighting and water regimes. Loss of trees due to beaver activities had increased lighting that made water heating more intense in spring. Because of damming a lot of standing water bodies appeared and diversity of habitats increased. Those facts were beneficial to spawning and metamorphosis of widespread species of amphibians - Rana spp., Bufo bufo. After a long-term influence of beaver activities in river valleys, the vast majority of suitable habitats for amphibians became associated with beavers, so species diversity within river valleys was increased, for example Pelophylax spp. appeared in beaver ponds. If beaver populations were young or unstable, reintroduction of beavers had small influence on amphibians, and in some cases their impact was negative. Factor of water regime had importance only in large beaver ponds, where beaver dams maintained stable water level. When beavers left ponds, especially in spring - a mass death of eggs and larvae was observed.