Squirrel energetics

Abstract

AbstractDirect calorimetry, respirometry and gravimetric techniques have been used independently to study the energy requirements of Grey and Fox squirrels (Sciurus carolinensis and S. niger, respectively). Studies using direct calorimetry and respirometry have produced similar values for the resting metabolic rate (RMR). In contrast to studies on other small mammal species, the average daily metabolic rate (ADMR), as measured by respirometry, has been found to be higher than RMR. RMR is closely correlated with temperature, and young squirrels require more energy per gram of body weight than adults; the effect of other variables on the metabolic energy requirements have not been studied. The experimental conditions of several gravimetric studies have differed and there is a consequent variation in the results; these data do not compare with ADMR values. The seasonal cycle in the daily duration of activity, the availability of food and the stress brought about by human disturbance and confinement in small cages, all affect the daily energy requirement of captive wild squirrels. Accurate analyses are hindered by the wide variation in results for individual squirrels and the difficulty in quantifying production and urinary losses. For these reasons, the compiled energy budgets of laboratory‐held squirrels are unlikely to represent the energy budgets of free‐living individuals or populations. Directions for future research are suggested.