Small mammals are an essential component of most terrestrial ecosystems. Monitoring is particularly important for this group of species in the UK because for many of them there is insufficient evidence for them to be assessed as part of the UK BAP process. This report proposes a unified approach to the monitoring of small mammals in UK and the Republic of Eire.

 

There is insufficient data on the majority of our small mammal species to be able to assess their conservation needs. One of the species for which there is concern is the harvest mouse, which has been proposed as a UK BAP species. However, more information about this species is urgently needed and the proposed national survey would seem to the only, effective, unified method for collecting this information. We have also included within the remit of the report the scarcer island species, such as the shrews of the Scilly and Channel Isles and the voles of Orkney and Guernsey. Although these species are not uncommon on mainland Europe, they represent outlying populations and considerably increase the biodiversity of the UK and Ireland.

 

 

Barn owls, and to a lesser extent other owl and raptor species, rely heavily on small mammals for their survival. Small mammals are also important for some of Britain’s scarcer carnivore species. For instance, the wildcat, pine marten and weasel are all proposed as priority species in the UK BAP review. Small mammals make up between 18 and 32% of the diet of the pine marten (Birks, 2002); mice and voles make up to 47% of the diet of the wildcat (Kitchener, 1995), and up to 90% of the diet of the weasel is small mammals (McDonald & Harris, 1998). As small mammals comprise such a large proportion of the diet of these threatened carnivores it is imperative that we implement a scheme to monitor their populations and thus contribute to the conservation of these carnivores.

 

 

Several small mammals appear to be affected by changes in agricultural practices. Bank voles are thought to be affected by pesticide drift into field margins (Macdonald & Tattersall, 2001). Field voles may be threatened by increased grazing pressure from stock, loss of rough grassland, the removal of linear features and loss of “marginal land” due to development (Battersby, 2005). The Orkney vole is an endemic species and is vulnerable to habitat loss and fragmentation through agricultural development (Harris, Morris, Wray & Yalden, 1995). Harvest mice are thought to be affected by changes in agricultural practices and management (Macdonald & Tattersall, 2002). The monitoring programme will include the collection of data on agri-environment schemes, farming practices and agricultural habitat. This will allow the influence of these factors on small mammal populations to be investigated.

 

 

Field voles and bank voles are known to attack young trees up to about 5cm in diameter and can cause considerable damage to broadleaved trees, pines, larches and even young Sitka spruce. They strip bark from roots and lower stems and bank voles are capable of climbing and may cause damage up to 4m high. Severe damage can cause death of the tree and less severe damage may allow fungal infections to enter the wood. Not only is the loss of trees ecologically damaging, but the preventative measures to ensure that trees are protected are costly. Wood mice can cause considerable economic damage to agriculture by consuming newly sown seeds and contamination of animal feed by faeces and urine. They have also been documented as carrying bTB (NFBG, 2004) and they carry a range of other zoonotic diseases including Weil’s disease (leptospirosis). They are also a common species found in homes where they can cause damage to woodwork and electrics. Yellow-necked mice have been linked to the spread of Tick Borne Encephalitis (TBE) across continental Europe and there may implications for the UK if the climate becomes warmer and the species is able to spread northwards across the UK (Battersby, 2005). House mice are economically important in Great Britain as they can cause extensive physical damage to buildings and wiring. and are known to consume and contaminate stored products. They carry several diseases including Salmonella, Cryptosporidium and Leptospirosis (Macdonald & Tattersall, 2001) and thus can pose a considerable health risk to humans.