Once exploited for fur, meat, and extracting the yellowish exudate called castoreum, the Eurasian beaver disappeared from Romania during the eighteenth century. After, the reintroductions carried out two decades ago are currently thriving in the Danube River basin. Using nine nSSR markers, we analysed samples from 98 individuals, and we found no genetic substructure, suggesting high dispersal and gene flow capabilities. The stepwise mutation model (SMM) indicated the existence of a recent genetic bottleneck, though the Eurasian beaver retains high levels of genetic diversity and population growth facilitated variation in nSSR loci. A fine-scale spatial correlation in females was detected, contrasting with males’ dispersal on longer distances. While the movement and establishment of individuals’ new territories were made under natural predation pressure, the mix following natural expansion improved the fitness and could contribute to a higher genetic diversity than the source population. With any reintroduction, a focus on capturing individuals from various geographic origins, as well as securing many and suitable founding individuals (adults, subadults, and juveniles) with mixed origins, could secure the post-genetic bottleneck recovery and higher genetic diversity. Beyond this conservation success, future management strategies should consider building a National Action Plan (NAP) for the species, including a permanent genetic monitoring programme for Eurasian beaver.

ABSTRACT. The reintroduction of Eurasian beaver (Castor fiber) in Romania started in 1998 and was a complete success in terms of population and natural range enlargement. The habitat modelling capacity of beaver was more and more obvious once with the increase of population densities, demonstrating the high potential of this species to create new trophic niches for other species and implicitly biodiversity enrichment. The study was conducted on a floodplain area near the Bârsa River, where the habitat became a vegetation and fauna paradise, by the constant intervention of beavers that had colonized the area in 2009-2010. In the first stage of this study, the habitats were classified and existing stands, shrubs and herbaceous vegetation was demarcated according to their composition and age (for tree vegetation). Further, a habitat analysis has been performed grounded on the correlation of dendrochronological sampling and satellite images captured between 2005 and 2014. On the basis of the aforementioned method, the right moment for beaver installation within the studied area has been determined quite precisely. This study is a clear example that beavers succeed to use in their best interest the opportunities offered by nature. Moreover, through the changes they produce on the environment, beavers have a strong impact on the natural succession processes.KEY WORDS: beaver repopulation, habitat modelling, beaver impact, dendrochronology. РЕЗЮМЕ. Реинтродукция евразийского бобра (Castor fiber) в Румынии началась в 1998 г. и увенчалась полным успехом в плане роста популяции и расширения ареала. Необходимость оценки емкости угодий становилась все более очевидной с увеличением плотности популяции, демонстра-цией высоких способностей этого вида в создании новых трофических ниш для других видов и косвенного увеличения биоразнообразия. Исследование было проведено в пойме реки Барса, где среда обитания стала природным раем и местом постоянного обитания бобров, колонизировавших этот район в 2009-2010 гг. На первом этапе исследования была проведена классификация биотопов и оценены запасы древостоя, кустарников и травяной растительности по составу и возрасту (после-днее -для деревьев). Далее был проведен анализ биотопов на основе корреляции дендрохроноло-гических проб и спутниковых снимков, полученных в период 2005-2014 гг. На основе вышеупомя-нутого метода достаточно точно был определен момент заселения бобрами района исследования. Это исследование -яркий пример успешного использования бобрами возможностей окружающей среды. Кроме того, путем изменения биотопов, бобры оказывают значительное влияние на сукцес-сионные процессы.КЛЮЧЕВЫЕ СЛОВА: репопуляция бобров, моделирование местообитаний, дендрохронология.