The latest report on the effect of beavers on woodland has been published by Scottish Natural Heritage (SNH), part of the ongoing monitoring work on the Scottish Beaver Trial.
A group of European beavers was reintroduced to Knapdale forest near Lochgilphead in 2009. The five year scientific trial is run by the Scottish Wildlife Trust and the Royal Zoological Society of Scotland, on land managed by Forestry Commission Scotland. Since their release, SNH has been closely monitoring the beavers, and their effects on the environment, in partnership with a number of other independent organisations. At the end of the trial, the results of the monitoring work will help the Scottish Government decide on the longer term future of beavers in Scotland.
The woodland monitoring has been carried out by the James Hutton Institute, who regularly survey 105 vegetation plots that are located around the edges of the lochs where the beavers live and are most active. In November 2011, two and a half years after their release, 13% of trees in the plots were showing signs of beaver activity. Most of these had either been gnawed or felled. As well as feeding on bark, twigs, shoots and leaves, the beavers store felled trees and branches underwater for food in the winter and use them to build their lodges and dams.
Between November 2010 and November 2011, there has been a minor shift in beaver activity to areas further from the waters edge, but the majority (72%) is still within 10 metres of the loch shores. The most intensive gnawing and felling was within 500 metres of active beaver lodges.
The beavers continued to favour trees that were 3-6cm across, although they sometimes felled much bigger trees.
So far the results show that the beavers have a strong preference for willow and rowan, and tend to avoid hazel and alder. Other trees in the area are used in proportion to their availability - birch is most often used by beavers but this is because it is the most commonly found tree in the survey area.
Many trees felled by the beavers regrow from the stumps. In November 2011, 35% of those felled had new shoots. The most vigorous resprouting was on ash, willow and rowan.
Glenn Iason, researcher at the James Hutton Institute, commented: “We are continuing to monitor the effects of beavers on the woodlands at Knapdale twice yearly. These early results are showing that beaver activity remains fairly close to the water’s edge. It will be interesting to follow the future survival and development of the new shoots, resulting from the beaver activity.”
Martin Gaywood, who leads the independent scientific monitoring of the trial for SNH said: “As part of the trial we are monitoring both the effects of beavers on their environment and want to gain a better understanding of their ecology in a Scottish context. This and other annual reports are vital to the trial, because they show us how beavers are getting on at Knapdale. At the end of the five year trial the results of the monitoring work will give the Scottish Government the information they need to decide whether beavers should be permanently reintroduced to Scotland.”