THE WESTERN BLACK-AND-WHITE COLOBUS AS A LOW-ENERGY STRATEGIST - ACTIVITY BUDGETS, ENERGY-EXPENDITURE AND ENERGY-INTAKE

1. Colobines are widely described as folivorous and a prediction of low basal metabolic rate appears to be supported by low activity levels, but energy budget estimates based on data from a field study of Colobus polykomos question these assumptions. 2. Annual diet and activity budgets are shown to change seasonally: unripe tree seeds are the preferred food type, with increased time spent feeding during the peak of seed production. Time spent resting is highest during wet seasons, when seeds are not available and only leaves are eaten. 3. The high energetic value of seeds compared to fruit flesh, young and mature leaves, is demonstrated. 4. Energy budgets are estimated for adult males and females (non-reproductive, pregnant and lactating), using daily energy expenditure (DEE) as maximum, and average daily metabolic needs (ADMN) as minimum values. 5. A simple model is employed to demonstrate that a diet of 100% seeds supplies sufficient calories for all estimates of energy intake and expenditure, whereas a diet of 100% leaves is unable to meet DEE and only the highest estimates of feeding rate (grams of leaves min-1) approach ADMN. 6. The advantages of detoxification, and the limitations of energy production for small-bodied fore-gut fermenters are outlined. 7. Evidence that C. polykomos is hypometabolic is considered, and it is concluded that the adaptations they show to periodic shortages of high energy foods are behavioural rather than physiological.