Monitoring red squirrels Sciurus vulgaris and grey squirrels Sciurus carolinensis in Britain

摘要: 1. In Britain, five indirect methods have been used to survey for the presence of red Sciurus vulgaris and grey squirrels S. carolinensis monitor population trends through time. These are: visual counts along line transects, use hair tubes, dreys, cone feeding transects in conifer forests signs on whole maize bait at stations. 2. Drey cannot differentiate between are not suitable areas where both species may be present. Hair tubes require expertise facilities identify hairs species, relationship tube visits animal density different habitats is only known Sitka spruce Picea sitchensis dominated plantations. Visual simplest method do little equipment. However, general, few seen a single count which leads difficulties estimating densities. 3. In this paper we present data from several studies carried out Britain illustrate type that collected, evaluate their accuracy precision with they could detect change. lines drey required fewest number samples When effort was also considered, were more economical. none monitoring discussed very precise it best terms relative changes numbers or indices time. 4. Our results illustrated change likely differ according size area. Monitoring programmes should therefore carefully planned relation spatial scale order able real changes. Species-specific, quantitative thresholds determine significance detected declines need established threatened UK mammals assessed what would constitute significant decline whether requires management intervention.