Energy flow through small mammal populations

Abstract

AbstractIn order to compile an annual or seasonal energy budget for a small mammal population, it is necessary to derive estimates of standing crop, consumption, egestion, digestion, excretion, assimilation, respiration, growth and reproduction. This review gives an account of the methods available for compiling such budgets, and uses results obtained from a study of Microtus agrestis in south west Britain as a worked example. This population was live–trapped on twenty occasions during the course of 2 years. Total energy flow was 309 kJ/m2 in the first year and 173 kJ/m2 in the second. The average coefficient of digestibility of the natural diet was 54–3%, the average net production efficiency was 1 –0% and the average gross ecological efficiency was 1 –2%. Peak energy flow occurred in spring and late summer each year, and coincided with peaks in the abundance and growth rate of the grasses which formed the main source of food. Previously published estimates show that the annual flow of energy is higher amongst small mammal populations inhabiting open habitats, such as grasslands, than it is in successionally more mature habitats, such as woodlands.