Historical presence of the Eurasian beaver (Castor fiber) in the IJssel River (the Netherlands) in 1450-1500

Author: Sanders Govaerts

Abstract: This article studies the presence of the Eurasian beaver (Castor fiber) in the IJssel River (the Netherlands) in the second half of the fifteenth century on the basis of preserved financial records. It argues that the beaver may have become functionally extinct in the Netherlands as early as 1500, several centuries before the last individual was reportedly killed (in 1826). The study also demonstrates the value of using medieval administrative sources to reconstruct the historical range of mammals in Western Europe. At least 153 beavers were presented to the city councils of Deventer and Zutphen in 1454-1489 in order to receive a financial reward. The species was hunted for multiple reasons, among which the prevention of economic damage was the most important. The introduction of a bounty system to capture beavers was probably a deliberate attempt to exterminate the animal. The presence of large numbers of beavers in the fifteenth-century Netherlands is remarkable, because the species may have become very rare or extinct in most of the Low Countries by 1400. Its possible reappearance and temporary recolonisation of large stretches of the IJssel River could be interpreted in the context of environmental changes. The digging of a new canal, which connected the city of Deventer with its German hinterland, may have created a new corridor that facilitated beaver migration from refugia in north-western Germany. The volume of water transported by the IJssel towards the Zuiderzee also declined significantly during the fifteenth century, which may have limited the species’ dispersal options and exacerbated conflicts with humans.