The ecology of small mammals, in particular Apodemus sylvaticus L. in a silvoarable agroforestry system

1. This research project on small mammals was carried out between December 1994 and August 1997 at the Leeds University Farms in West Yorkshire. 2. Densities of captures were assessed using weekly live trapping and mark- release-recapture (MRR) methods. One hundred and thirty two Longworth traps were set out in a complex fanning landscape consisting of four replicate blocks of silvoarable agroforestry designed as a series of tree rows planted at low density (178 trees/ha) and separated by arable alleys cropped with cereals (wheat or barley). Adjacent to each of these agroforestry systems is an area of trees planted at forestry density (2500 trees/ha), an arable field and a mature hedgerow. 3. Overall 1680 captures were obtained, 70% of which were of Apodemus sylvaticus, 20 % of Sorex araneus and only 10% of Clethrionomys glareolus. 4. A. sylvaticus and S. araneus showed preferences for the agroforestry system, whereas C. glareolus prefered the mature hedgerows. Overall, the highest density of capture was found in the tree rows (13.4 animals per 100 trap nights) and the least in the arable field (4.2 animals per 100 trap nights) 5. Densities of captures of A. sylvaticus were greater in Autumn than the other seasons, notably in the tree rows when the arable areas provide little cover. 6. Population densities were calculated and showed the same seasonal pattern as densities of captures. The highest population density was in October 1996 (36 mice/ha). 7. Male A. sylvaticus bred extensively from mid-Winter until early Summer. The female had a longer and more sporadic breeding period. Overall, the animals showed little or no breeding condition during the phase of population increase in the Autumn-Winter period. 8. Radiotracking of A. sylvaticus was carried out from May 1996 until June 1997. Home ranges were estimated using cluster analysis. 9. Home range sizes of A. sylvaticus, estimated using 95% of the density distribution, were between 0.04 and 0.30 ha. Home ranges of males were larger than those of females and showed seasonal patterns, with larger ranges during the Spring-Summer period which corresponds to the breeding season. 10. All the individuals tracked had overlapping home ranges spreading over the different habitats, particularly in the agroforestry system (tree rows and arable alleys) where most of the activity of the animals was recorded throughout the year.