There have been at least 161 reintroductions of beaver in Europe since 1924.
Studies show that following release they disperse widely throughout a watershed and then gradually infill.
Population growth is slow for the first ten years and then increases more rapidly until all suitable habitat is occupied.
It takes about 30 – 40 years to reach this stage of completed colonisation and populations then stabilize, with beaver moving into more marginal habitat areas which are often then abandoned.
Because beaver are reluctant to move far from water, they are generally contained between watersheds. Man-made dams also act as an effective barrier and beaver ladders have been installed in several countries, notably France, to permit colonisation beyond them.
Watershed ridges and areas of full urban or intensive agricultural development also present strong barriers to spread.