Energy Metabolism and Food Consumption by Wild Howler Monkeys (Alouatta Palliata)

Rates of CO2 production in free—living and captive howler monkeys were measured using doubly labeled water, and assimilation of energy from natural foods was determined. Results permit construction of a field energy budget, and estimation of the feeding rate of these arboreal, plant—eating primates. Field metabolic rates averaged 355 kJ kg—1 day—1 (°2 x basal metabolic rate). Assimilation of the energy in a fruit and leaf diet was °40%. Feeding rate in the field is estimated to be °54 g dry matter kg— day—1, or °90 kg dry matter ha—1 yr—1.