Bashinskiy I.V., Osipov V.V. 2016. Beavers in Russian forest-steppe — characteristics of ponds and their impact on fishes and amphibians // Russian J. Theriol. Vol.15. No.1: 34–42 [in English].
Ivan V. Bashinskiy [corresponding author, ivbash@mail.ru], Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninskij prosp. 33, Moscow 119071, Russia; Vitaliy V. Osipov [osipovv@mail.ru], Privolzhskaya Lesostep’ State Nature Reserve, Okruzhnaya 12A, Penza 440031, Russia.
ABSTRACT. The study of beaver’s (Castor fiber) impact on steppe rivers’ ecosystems was held within the Privolzhskaya Lesostep’ State Nature Reserve (Penza Province, Russia). We investigated how pond age and permanence of beaver ponds influenced the abundance and diversity of fishes and amphibians. The majority of beaver ponds in our study area were small and dams were easily destroyed by spring floods. The formation of stable long-term ponds was evident in rivers with low discharge. The most favorable parts of rivers for beavers were anthropogenic reservoirs, where swamping and high biomass of reeds were common. The rivers were inhabited by one species of lamprey (Eudontomyzon mariae), six fish species (Esox lucius, Leucaspius delineatus, Sabanejewia baltica, Misgurnus fossilis, Barbatula barbatula, Carassius carassius), and five amphibian species (Lissotriton vulgaris, Pelobates fuscus, Bufo viridis, Rana arvalis, Pelophylax lessonae). As a result of the damming, abundance, biomass of fishes, species diversity and abundance of amphibians increased. During long-term persistence of beaver ponds fish abundance declined (the oxygen level reduced), but the number of amphibians continued to appear (more shallow water bodies appeared). Also beaver dams led to isolation of fishes in different parts of valleys and served as barriers to spawning migrations (e.g. for pike and lamprey). When beavers abandoned ponds, amphibian abundance declined, and fish abundance increased — due to increased water flow. Thus, despite some positive effects, beaver ponds were not the key habitats for fishes and amphibians.
KEY WORDS: Castor fiber, impact on ecosystems, fishes, amphibians, small rivers, forest-steppe.