The short-term impact of Eurasian beavers (Castor fiber) post-reintroduction on amphibian abundance and diversity in a lentic environment

Abstract

In 2021, eight Eurasian beavers (Castor fiber) were reintroduced into the Idle Valley Nature Reserve (IVNR), Nottinghamshire, England. Amphibian surveys were conducted in four areas within the IVNR prior to the beaver reintroduction to establish baseline data. To investigate the short-term impact of beavers on amphibian abundance and diversity, this study sampled the same four areas post-beaver reintroduction. An additional four areas were also sampled post-beaver reintroduction, to compare areas where beaver activity was present or absent. Furthermore, environmental, and beaver-linked variables were analysed to predict adult amphibian abundance. Adult amphibian abundance dramatically increased post-beaver reintroduction. However, there were no significant differences in adult amphibian abundance between areas where beaver activity was present or absent, with only increasing water depth and surveying at night shown to be significantly positively related to adult amphibian abundance. Conversely, there was a significant difference in terms of environmental variables between areas where beaver activity was present or absent. Similarly, beaver active areas were found to have higher young amphibian recruitment. Thus, the reintroduction of the beavers has not had a negative short-term impact on amphibian diversity and abundance, with the findings suggesting that over time the beavers will have a positive impact.