A tale of tails: the use of Eurasian beaver (Castor fiber) tails for ageing and individual identification

With increasing technology and knowledge, the range of methods used to monitor wildlife is growing. As many invasive techniques have been shown to negatively impact study populations, the use of non-invasive methods is increasing. With Eurasian beaver ( Castor fiber ) reintroductions occurring across much of Europe, monitoring of beavers is becoming increasingly important; however, some frequently used techniques are invasive. We therefore aimed to examine potentially non-invasive methods of identifying and ageing them from the tail. Tails from previously deceased beavers were photographed with a Nikon D3500 DSLR camera across 3 distances: ‘close’, ‘medium’ and ‘far’, and the pattern of the scales were examined by eye to determine accuracy of individual identification. Photographs including a grey standard were used to determine the accuracy of ageing beavers from the colour of the tail. The accuracy of individual identification was 100% across all distances; however, the results from ageing showed the method to be inaccurate. The success of the individual identification shows that this method could be effectively used as a non-invasive method for monitoring beaver populations, especially in captivity.