KNOWLEDGE BASE

Beavers and beaver dams are very common in subarctic wetlands. This study showed how beaver dams in these areas change water flow by creating ponds that, through flooding, store more water and increasing water evaporation. The dams also regulated water flow in different ways, and created complex drainage patterns across the wetlands.

This paper used 46 years of aerial photographs to analyse how beaver pond creation changed over time. In this site in the USA, pond creation slowed after the first 20 years because the landscape limited where beavers could build large dams. While beaver colonies continued to grow, fewer new ponds were created, and the ponds made later were smaller than those made in the early years. Please note, this resource is not open-access.

This paper reported on beaver foraging of trembling aspen in northern Minnesota, USA. They showed that most of the wood harvested by beavers was used in dam construction or left on the ground, rather than eaten. Harvesting also reduced aspen density by up to 43% in the areas around the ponds, and beavers' selective feeding changed the forest composition, favouring species like alder and spruce. The authors suggested this could impact long-term forest dynamics. Please note, this resource is not open-access.

This study is an early example of how GIS computer software was becoming an "essential tool" in landscape ecology studies of beavers. Here, 46 years of aerial photographs were analysed alongside field data to show how beavers affected hydrology and vegetation. Beaver ponds expanded from 1% to 13% of the landscape, increasing nitrogen stocks in the landscape almost threefold. Most pond growth occurred in the first 20 years, with water depth and vegetation stabilising afterward.

Between 1980-1986, 81 wolves were studied in the USA. The study monitored their pack size, dispersal patterns, and diet. Deer were wolves' primary winter prey, but beaver were shown to be an important secondary prey - particulary in April and May where they could make up almost half the wolf diet, before diminishing over June and July.