A while ago I found this interesting material about the reintroduction of Beaver in the Province Limburg, The Netherlands. European beavers do not build the large lodges and extensive dams so easily visible on high resolution satellite images. So they are a lot more difficult to spot on GE.

The organization ARK (http://www.beversinlimburg.nl/)plays an important role in the reintroduction of beavers in the areas along the river Maas in the Netherlands.

Between 2002 and 2004 33 beavers were reintroduced in Limburg.
They play a key ecological role along the banks of the river Maas and its creeks.

The population has grown to over 100 beavers and would be considered sustainable if it exceeds more than 125 animals.

The attached kmz envelope groups the kml for the various sites, gives a brief description, and an excellent series of photos showing the locations of beaver habitat and presence.