Effect of supplementary food on the ecology of wood mice (Apodemus sylvaticus L.) living in a sand dune habitat
The purpose of this study was to test the hypothesis that food availability was responsible for the low population density, larger home range size, high degree of daytime activity and longer activity periods of wood mice living in a sand dune habitat compared to those living in deciduous woodlands in Grampian, North-East Scotland. An experiment was set-up whereby one population of mice was provided with superabundant food in the form of wheat and the parameters mentioned above were measured and compared with an adjacent control population with natural levels of food. Seasonal changes in population density, demography and breeding biology were obtained via live-trapping. The home range size and activity patterns were measured by the use of radio-telemetry. The presence in. or absence from the nest was recorded automatically by a minichart recorder. The supplemented population had a higher density (2-3 times), higher recruitment rate (2-8 times), earlier start to the breeding season, increased juvenile recruitment and lowered weight of sexual maturity compared to the control population. Supplemental food did not prevent the normal population decline over winter, improve survival rates or extend the breeding season into winter. It was concluded that food interacts with behavioural and other environmental factors to. limit population density. The supplemented mice had significantly smaller home range sizes both in the breeding and non-breeding seasons compared to the control mice. The supplemented mice moved significantly shorter distances per night compared to the control mice. The supplemented mice were strictly nocturnal, emerging from the nests after sunset and returning before sunrise, and spent significantly less time active, both in the breeding and non-breeding seasons compared to the control mice. No regular short-term rhythms were observed in the individuals monitored in both populations. Diet analysis showed that the mice were feeding mainly on arthropods throughout the year. The low density and mobility of the food resources would account for the differences in home range size and activity patterns of the control mice mentioned previously.