Exploring Beaver Habitat in Europe:
Republic of Karelia, Russia
The history of beaver in Europe is as interesting as it is in North America. There are many parallels: over hunting to satisfy demand for its fur in the European fashion market and its recovery through conservation, reintroduction and fortunately, disappearance of the market demand for its fur.
We know now that two different species of beaver are involved in this story, but in some of the early restoration initiatives in Europe, North American beaver (Castor canadensis) was thought to be genetically identical to the European beavers and were introduced in Sweden, Finland, and Karelia. They are now considered as invasive species in the areas originally inhabited by the Eurasian Beaver (Castor fiber). In areas where the two species occur together a struggle for dominance have seem to end in favor of the North American intruders. This struggle for dominance has been of much interest to scientists as well as newspaper media in Canada.
Google Earth has proven to be an effective tool in mapping and monitoring changes in beaver habitat in Canada and locating exceptional beaver communities, beaver landscapes and locating long beaver dams, and high density populations. The objective of this study is to see if Google Earth can be used in Europe to locate and monitor beaver activity in a similar way.
In addition it has been reported that North American beaver tend to build longer dams than their European hosts. This raises the question: Could the longest beaver dam in Europe be build by a Castor canadensis?
- Finland- an early reconnaissance of beaver habitat study with Google Earth was not very promising, some areas with active beaver were identified; further work will be done at a later date; some dams were spotted near the border with Karelia;
- Karelia-Republic in the Russian Federation- In areas where Google Earth high resolution imagery was available beaver activity, beaver damage (tree kill) and sometimes beaver dams could be located. About 100 beaver activity place markers were posted on the Google Earth Community Forum (April 2011) are included in this Google Earth KMZ file.
- The longest beaver dam in Karelia found (in this survey) with Google Earth was 230 meters long in an area in which the North American Beaver dominates. This is 50 meters longer than a 180 meter beaver dam in Belgium which is 'claimed' to be the longest dam in Europe. It is probable that when more high resolution Google Earth imagery becomes available in Karelia a longer beaver dam will be found.
Over hunting reduced Eurasian Beaver (Castor fiber) populations to c. 1200 animals, in eight isolated populations, around the end of the 19th century.  Protection, natural spread and reintroductions led to a powerful recovery in both range and populations during the 20th century, which continues at a rapid pace. The minimum population estimate is 593 000. They also reported that there are also c. 12'500 North American Beaver (C. canadensis) established in Finland and Russian Karelia; however, other populations of C. canadensis introduced in Austria, Poland and France appear to be extinct.
During 1935 and 1937, seven C. canadensis from the USA were released in Finland together with the 17 Scandinavian beavers. Descendants from the North American beavers at Sääminki were subsequently translocated to other places, including Lapland. At present, C. Canadensis numbers 3300-5200 in Finland (Lahti, 1995). North American beavers immigrated into Russia from Finland in the 1950s. This immigration was boosted with the release of six C. canadensis near lake Onega in 1964 (Safonov, 1975). In 1989 their number in Karelia was estimated at c. 2000 (Ermala et al., 1989).
In 2002, Geoffrey York reported in the Globe and Mail : "The Canadian beavers were introduced in the 1950s and 60s into Finland and Sweden, where no native beaver population existed. With no natural predators, they swiftly expanded their area. Beginning about 25 years ago, they spread from Finland into the northern Russian region of Karelia, where they continued to expand. Up to 20,000 Canadian beavers are believed to be thriving in northwestern Russia today, and scientists predict they will soon march further south, rudely shoving out European beavers as they go. The Canadian beavers seem to have more stamina and flexibility, they are more active and they can survive better.
One of the main differences between the two is that Canadian beavers build dams -- sometimes huge structures up to hundreds of meters in length -- while European beavers generally don't"
A 2008 article in Canada’s MacLean’s Magazine by Malcolm Gray[3)]drew again attention to the problems that the North American beaver are causing in Russia. To quote part of the article:
“Not only do the Canadian interlopers have sharper teeth and more energy, those eager beavers have better engineering skills than the Russian rodents they are displacing. They build bigger, higher dams — some as long as 100 m — reproduce more quickly than the locals, and have few natural predators to keep their numbers in check. Disgruntled officials grumble that beaver dams drown forested areas, killing commercially valuable trees, and complain that the animals' tree-felling activities often leave adjacent farmland vulnerable to erosion. As well, say the officials, the 20,000 Canuck beavers in northwestern Russia are a health hazard as their water-borne feces contains such diseases as giardiasis, or beaver fever, an intestinal illness spread by a microscopic parasite.”
The two newspaper articles inspired a closer look at beaver habitat in Finland an Karelia. Surely with the reported damage that beaver seem to have caused it should be possible to see this with Google Earth. At the same time it would be interesting to find out how the North American beaver was building its dams in Europe.
An early reconnaissance of Finland was not very promising. Although Harkonen (1999) reported a 2.2 ha average size of forest damage by Canadian beavers, very few beaver impacts areas could be found with Google Earth. The study also noted that most of the damage occurred in peat land forest.
Halley and Rosell provide a small scale map of beaver distribution in Eurasia . It shows the location of the aerial extent of the European beaver as well as the North American beaver. The most authoritative maps for the distribution of beaver around the world are provided by the IUCN Species Survival Commission through its 'Red List' web site. However, the Red List site does not provide distribution maps for invasive species, like the North American Beaver in Europe.
Durka et al. 2005  provide a map, based on Halley and Rosell, which shows a bit more detail related to the distribution of the American beaver in Finland and Russia. The map below superimposes their information, a blue overlay, on the IUCN the distribution of the Eurasian beaver map. The red striped areas show the Eurasian beaver distribution , the light blue the area shows the American beaver occurrence.
During 1935 and 1937, 7 C. canadensis from the USA were released in Finland together with the 17 Scandinavian beavers mentioned above. Descendants from the North American beavers at Sääminki were subsequently translocated to other places, including Lapland. In 1995, C. Canadensis numbers 3300-5200 in Finland (Lahti, 1995) . North American beavers immigrated into Russia from Finland in the 1950s. This immigration was boosted with the release of six C. canadensis near lake Onega in 1964 (Safonov, 1975). In 1989 their number in Karelia was estimated at c. 2000 (Ermala et al., 1989).
Nummi (2007) provides an overview factsheet of the American beaver as an invasive species. There is a possibility of competitive exclusion of Castor fiber by C. canadensis (Nummi 2001) due to higher reproductive output, since litter size is bigger in C. canadensis (Danilov 1995). Competitive displacement of C. canadensis by C. fiber can be seen in the South of the Russian side of Karelia (Данилов 2005). C. canadensis seems to be a little more active constructor of dams and lodges than the Eurasian species. Otherwise the ecological engineering by both species have a similar keystone effect on various plant and animal species, including fish, amphibians and birds (Rosell et al. 2005).
C. canadensis and C. fiber do not hybridize, due to the difference in chromosome numbers (Lavrov 1983).
A Number of Examples of Beaver dams and beaver activity in Karelia
West of Lake Ladoga
West of Lake Onega
North East of Lake Onega