engleski

The importance of beaver (Castor fiber L.) for preservation of small streams

Beavers are known as one of the "greatest constructors" in animal kingdom. Their building skills don't just result in creating imposing structures (lodges and dams), but also have the impact on the habitat respectively on the ecosystem. Our first surveys of these structures and their impact on the ecosystem started when beavers (Castor fiber L.) made their first dams on Croatian territory. Special attention was given to dams on smaller streams, which have a very low flow or even droughts during summer. What is the significance of structures that beavers build on small streams? Primarily, a major contribution of beaver dams is retaining water in the lakes that are essential for the conservation of aquatic and wetland ecosystems. The second role is providing water for the entire fauna around the lake. In this way beavers provide their basic requirements essential for their staying on the same site. Analysis of beaver dams and accumulation have shown that with very small dams (or series of dams) level 30-40 cm and a width of 5-8m, in which they incorporate only 1-2m3 of material, beavers create a series of lakes which then generate the basic living conditions and accumulate 40-50m3 of water. On narrow streams beavers typically raise more dams that are up to 2 m high, 8-10(15)m in width which incorporate 20-50m3 of material while the lake reaches capacity between 400m3 and 3000m3 of water depending on the length, or trough decrease. Otters appear regularly on such lakes, due to the favourable conditions that are created for fish, bivalves and crustaceans. Storks are always present along the lakes and there is also increased number of wild ducks (waterfowl in general). Due to the very intensive stream regulation that is being done nowadays, beaver activity plays a crucial role in the survival and conservation of flora and fauna of small streams.

small streams; beaver dams; ecosystem

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