Beaver (Castor fiber) in Denmark

The beaver was absent from Denmark for more than one thousand years before the species was reintroduced in October 1999 and 2009. In the initial reintroduction, eighteen beavers captured in Germany were released at six different sites within Klosterheden State Forest in the northwestern part of Denmark. Later, between 2009 and 2011, six additional beaver families, totaling 23 animals, were captured in Germany and released in North Zealand. Together, these efforts have contributed to establishing new and healthy populations of beavers in Denmark.

Large areas in the country have been drained due to intense agricultural use and forestry. One of the main reasons for reintroducing the beaver was because of its ability to create dynamics in its surroundings. By cutting down trees clearings are made which allow for the growth of light-demanding plant species and by building dams beavers flood areas creating new habitats for many species of insects, amphibians and birds.

Klosterheden State Forest is approximately 7000 hectares of mainly coniferous forest planted on former heath land. Small streams run in the valleys and non-coniferous trees growing in these valleys are mainly willow ( Salix sp.), birch ( Betula pubenscens and Betula pendula )and bug myrtle ( Myrica gale ). At several places within the State Forest the streams have been artificially dammed and small lakes and ponds created.

The eighteen beavers released in 1999 included 12 adults, 4 juveniles and 2 kits less than one year old. Beavers captured within one particular beaver territory in Germany were released at the same release-site in Denmark.

The Arresø catchment area covers approximately 216 square kilometers and consists of several larger and smaller lakes as well as multiple streams of varying sizes. 

Between 2009 and 2011, 23 beavers were released into Arresø and its surrounding area. The beavers were captured from the Elbe River in the Wittenberg-Leipzig region (Saxony-Anhalt in Germany). They were captured from different locations to ensure they belonged to distinct families, aiming to provide as genetically diverse a population as possible.

 

Monitoring and status

The beaver is nocturnal and therefore observing the animals is a difficult task. Fortunately the beavers’ way of living ensures that their presence is confirmed by a lot of visible evidence such as de-barked branches, dams and scent mounds.

As beaver forage on branches they de-bark them and often leave the branches behind at the waters’ edge but some are used as dam-building material. Short trails lead from the water to foraging sites and tree stumps resulting from beaver felling project from the ground.

In late autumn some beavers make food caches. These are big gatherings of branches secured to the bottom of the lake or stream in front of the beaver den. In this way beavers have access to food even in severe winters where the water freezes over.

Beavers build dams to ensure that the water level always covers the entrance of the den and to facilitate the transportation of both building material and food items. Dams are often built in the core area of the territory. In Klosterheden State Forest the highest beaver dam measures 1,2 metres and the longest meassures 74 metres.

Beavers scent mark by depositing a secretion (castoreum) on scent mounds, which are piles made of mud, debris and plant material scraped together by the beaver. The main function of scent marking is the maintaining of territorial rights. As most scent mounds occur near the den or at territory boundaries it is possible to determine the approximate size on a territory on the occurrence of scent mounds.

Monitoring of the beavers in Denmark include recording of the visible signs of beaver activity in all recognised territories and also by searching the water system for new signs of activity from a canoe or by foot.