Berthelsen, J.P. 2008: Overvågning af bæver Castor fiber i Danmark 2006. Danmarks Miljøundersøgelser, Aarhus Universitet. 44 s. – Arbejdsrapport fra DMU nr. 243.

 

English summary

After the release of beavers in October 1999 in Klosterheden State Forest in the vest of Jutland (SNSV) the natural conditions in the beaver activity areas have been investigated and surveyed. The National Environmental Research Institute (NERI) undertook the technical coordination and reporting with regard to the monitoring of beavers during the period 1999-2006. In 2006 fieldwork and monitoring were carried out in collaboration with NERI. The 2006 annual report on the beaver monitoring and survey in 2006 was prepared by NERI based on data from SNSV and provides an update of the status of the population, primarily with focus on growth, distribution and mortality by the end of 2006.

 

Population growth, development and distribution

An important element in the beaver monitoring program is the annual beaver count in spring, which is carried out systematically in all beaver territories. The count in 2006 was carried out following the same procedure as in previous years involving a large number of volunteers. Mapping the spots and localities with beaver activity was based on traces of gnawing, cutting and felling of trees. Along the more inaccessible stretches of watercourse beaver activity was surveyed from canoes. On the basis of the actual number of observed individuals, the total beaver population in the breeding season of 2006 was estimated at a minimum of 89 individuals, including 13 juveniles. A total of 26 beaver territories were registered.

 

Registrations of dead beavers

There were no official observations of dead individuals or remains thereof in the SNSV area in 2006. In general it is not possible to calculate or know the precise mortality in a beaver population. It would seem most likely that dead animals or remains would be found and reported in localities within the state forest, because of the large number of visitors and unlimited public access to the beaver territories here. Public admission to territories situated on private land on the other hand is limited, and for that reason the level of random monitoring and probability of finding dead individuals is probably lower.

 

Description of beaver territories

Since 1999, annual registrations of beaver numbers and the status of the dispersal of beaver territories have been carried out. Within the territories beaver activity areas are monitored and mapped based on definite traces of gnawing and felling of trees. In 2006, all beaver territories were surveyed. The location of beaver territories remained largely unchanged compared with the situation in 2005; however the natural conditions were not investigated this year. Home ranges within these territories have changed and in several cases they have been split up. At the end of 2006 there were a total of 11 territories in the SNSV area, and 15 territories in the landscapes west and south of SNSV. In some territories occupied by beavers over a number of years the core areas of beaver activity have changed within the territories.

 

The impact on areas of production and the contact with

riparian owners

In 2006 all registered beaver lodges were supervised and landowners with beaver activity on their property were contacted by SNSV staff. If and when problems arose the staff, in consultation with the landowners, undertook some form of remedial action. Overall, there were fewer incidents and complaints registered in 2006 compared to the previous years, despite the increase in the beaver population and dispersal into new habitats.

 

Information and communication with the public

In SNSV there is generally a great focus on wildlife aspects, public access and opportunities for nature recreation in the forest. On the homepage of the Danish Forest and Nature Agency information including the reintroduction of the beaver in Denmark is available. In 2006 there was still considerable public interest in visiting the beaver sites. The staff from the SNSV arranged a total of 75 guided tours with a total of 2,250 participants as well as 10 fieldtrips with a total of 300 participants. The concept of a bus equipped with a wide rang of equipment was a success with a total of 85 tours. Interest from the press has continued via a number of articles and reports.

 

Moreover, staff from NERI and SNSV presented two papers at the 4th International Beaver Symposium in September 2006 in Friesing, Germany.

 

New project on beaver monitoring

A new master thesis on aspects of beaver monitoring will be initiated in Klosterheden in 2007. The aim of the project is to develop a new method for estimating the size of the beaver population and to monitor beaver signs in order to develop a tool for conservation use. At the present time, the size of the beaver population is estimated from sight observations in the springtime, where the beavers are counted by several observers at sunset and sunrise. This method is limited by the dark hours, and this study aims to test if spotlight counts can supplement or substitute the presently used method. The survey takes place in March and early April. GPS-registration of beaver lodges, beaver dams and cuttings is conducted on an aerial photograph and these data are transferred to a GIS. Changes over time in the size and condition of wetlands caused by beaver activity will be monitored through comparison of time series of aerial photographs. Data will be digitized and included in the database. On the long term it will be possible to follow the annual changes in the landscape created by the beaver. The database is expected to become a useful tool for management of the beaver population in Klosterheden.

 

Full repport  in pdf-format (2,139 kB)