Fantastic beavers (Castor fiber) and where to find them: Using availability of suitable habitat to estimate beaver populations sizes
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The Eurasian beaver was significantly over harvested for its pelt and for what is called castoreum, and the global population was estimated to be 1200 individuals. Today, the Eurasian beaver population is estimated to be approximately 1,5 million individuals spread across a major part of their former distribution range, due to protection of the species internationally and reintroduction programs. The increase in populations leads to a need for a way of estimating population sizes. This thesis’ aim is to see if a standardized method can be used to estimate beaver populations accurately. The method uses sign surveys to map suitable habitat, and estimates population size based on the availability of suitable habitat in the study area. I found that the suitable habitat in the area was agricultural- and mixed forest landscapes with waterbody gradients between zero and ten percent slope. The study area has a total of ~18 square kilometer suitable habitat, which leads to a population estimate between 72 – 135 individuals. These estimates seems to be a little high compared to two other methods for population estimation.