The diet of field voles Microtus agrestis at low population density in upland Britain

Studies on field voles Microtus agrestis Linnaeus, 1758 in lowland grasslands have shown them to be unselective grazers. The diet of the field vole in upland Britain was investigated using feeding trials with four of the dominant British upland monocots, Molinia caerulea, Nardus stricta, Deschampsia flexuosa and Eriophorum vaginatum. The suitability of faecal analysis was assessed and then used to analyse the diet of wild voles from faecal samples. Percentages of plant species in the faeces were compared to percentages on the ground in sites dominated by Molinia caerulea, Eriophorum vaginatum, Nardus stricta and Calluna vulgaris. Significant preferences for the grass Deschampsia flexuosa were observed in feeding trials and in the wild while the sedge Eriophorum vaginatum was avoided in both. There was no clear preference for Molinia caerulea and Nardus stricta. Preference for plant species was related to palatability and nutrient content. The low nutrient conditions in British uplands mean that voles that live in these environments must be selective feeders to maximise nutrient intake.