Published in support of the UK Biodiversity Action Plan for black grouse

Causes of decline

Deer

Deer are Britain's largest native land mammals and the two native species, red and roe, have an important part to play in woodland and other ecosystems. They can be important in maintaining a mosaic field layer in forests (important for woodland grouse) and keeping vegetation short on bogs (good for breeding waders). They also give enormous pleasure to people who marvel at their beauty and wild nature, shared by those who enjoy watching them and those who hunt them. Deer are also a valuable resource in terms of employment generated in their management and in the venison produced. They should be an unqualified public benefit but sadly, because of poor management over many years, deer are in danger of being regarded as a pest.

Rising deer numbers can have detrimental consequences for agriculture, forestry and the natural environment. In particular, prevention of woodland regeneration and possibly local heather loss have been attributed to overgrazing by deer in several parts of the Highlands. On sites where there is clear evidence of damage, the Deer Commission for Scotland is developing deer control programmes. In these areas, large initial culls may need to be taken in order to bring numbers down. Once numbers have been reduced, a maintenance cull has to be taken in order to cull the annual recruitment to the population or to take out animals which have moved on to the site from other areas.

Grazing by red and Sika deer in Scotland (combined with grazing by sheep in some areas), has led to a decline in the quality and area of many moorland and woodland plants. Black grouse depend on these plants for food and to provide cover for nesting, brood-rearing and roosting. Heavy grazing of heather favours grasses that are less nutritious to black grouse and hold fewer insects for their chicks. Browsing by deer also prevents the regeneration of native woodlands that could provide valuable future habitat for black grouse. In order to prevent damage to native woodland regeneration (as well as forestry plantations), high fences have been erected, but these cause equally serious problems for black grouse.

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Red deer stag: heavy grazing and browsing in some areas of Scotland can reduce the plants that black grouse need. Chris Gomersall (RSPB-Images _009)

Sika deer are an exotic introduction from over a century ago and are causing significant damage. Current national policy, established by the Deer Commission, is to prevent sika from becoming established on open hill ground and vigorously control them in other areas. Numbers of red and Sika deer have increased significantly in recent years and now number at least 400,000 in Scotland, more than at any time since before the last Ice Age. This has been encouraged by milder winter weather and a decrease in culling rates. Their densities can be as high as 20 deer per square kilometre (0.6 miles) in prime black grouse habitat.

What can be done?

Other factors in the decline
Agriculture
Fencing
Forestry
Predation
Shooting
Weather