The Scottish Beavers Network - campaigning for the Reintroduction of the European Beaver into Scotland

 

The Effect of European Beavers on Other Wildlife Species        

Invertebrates

Beaver ponds both slow the flow of a watercourse and increase the surface area of water. In the slower stream sections such as beaver ponds, the density and number of species of aquatic invertebrates can be several times higher than in faster sections. The increased surface area created by the pond allows a larger amount of leaf litter to fall into the water thus providing more food for the aquatic invertebrates as well as allowing more habitat for other invertebrates such as dragonflies. In some studies, the number of dragonfly species has doubled or even trebled after beaver activity. Beavers create a variety of deadwood habitats for invertebrates by directly felling trees and by flooding woodland through dam building.

 Fish

The increase in aquatic and semi-aquatic invertebrates results in greater feeding opportunities for fish, particularly non-salmonid species that feed on bottom dwelling invertebrates which prefer slower moving sections of a stream.

However, the deeper water of beaver ponds can provide important habitat for salmonids during the winter and in times of drought. In addition, the ponds offer good holding areas in streams lacking similar features for migrating adult salmonids and large resident trout. Far more large trout in Russia are found in watercourses inhabited by beavers. Studies from the US with North American beavers show that warm water fish such as minnows increase in beaver ponds while pike numbers rose in larger ponds with shallow grassy areas. 

Birds

By stabilising wetlands through dry periods, beaver dams increase breeding habitat for waders and ducks. Mallards, teal and goldeneye in particular nest on beaver ponds, and in Latvia, a dramatic increase in the populations of cranes and black storks was as a result of numerous ponds created by the expanding beaver population. Fish-eating birds such as goosanders, mergansers, herons and kingfishers also benefit from the array of fish attracted by the slow-moving waters of the pond. Marshier conditions are beneficial to redshank and snipe, while wetter woodlands are more attractive to woodcock. Insectivorous and hole-nesting species such as woodpeckers and willow tits benefit from the proliferation of decaying wood created by the beavers' dam building activities, while tall marshy vegetation supports reed buntings and warblers. 

Mammals

The presence of beavers would have a positive impact on other Scottish mammals. In Europe, beaver and otter territories frequently overlap and beaver ponds are particularly important for otters in areas where deep water habitat is limited. 

Beaver ponds provide otters with a plentiful food supply of fish as well as an area of stable water levels with plenty of vegetational cover suitable for denning while abandoned beaver lodges and burrows themselves may be used by otters for shelter. Water voles, which have suffered a dramatic population decline in recent years, would benefit from the creation of grassy margins at the edge of the beaver pond. In addition, like otters, water voles and water shrews would use beaver lodges and burrows for denning. 

Other herbivores would benefit as deer would also feed on the aquatic and semi-aquatic grasses growing in the pond, while hares would feed on the bark of trees felled by the beavers.

In Europe, bats also nest in standing deadwood caused by rising water levels brought about by beaver dams, as well as feeding on the increased numbers of flying insects.