Energy consumption of small rodent populations in two Irish woodland ecosystems

Abstract

The energy flow through populations of wood mice Apodemus sylvaticus and bank voles Clethrionomys glareolus was studied in an oak Quercus petraea wood and in a yew Taxus baccata wood at Killarney, south-west Ireland, from 1975 to 1977. The energy requirements of the populations were calculated from capture-recapture data using information on metabolic rate, assimilation coefficients and calorific value of body obtained from the literature -data for Apodemus flavicollis was. of necessity, substituted for A.sylvaticus. The proportion energy devoted to production was 2.8 to 3.3% of assimilated energy for mice and 2.3 to 2.5% for voles. The proportion of available, palatable fruit material consumed varied considerably, from 6.5 to 50.8%, depending on the size of crops and on the size of the small mammal populations. Overall, however, it was low: 13% in the yew wood and 12% in the oak wood, averaged over the period of study. The proportion of primary production consumed did not show as much variation, the values ranging from 0.16 to 0.37%; It was concluded that small mammals in woodlands are generally inefficient consumers of fruits because of the dramatic seasonal and annual variations in fruit fall.