LIMITS TO THE ENERGY BUDGET IN A RODENT, PEROMYSCUS-MANICULATUS - THECENTRAL LIMITATION HYPOTHESIS

The maximum rate of energy assimilation in lactating Peromyscus manicu latus (100 kJ/d, body mass = 25 g) was lower than in cold-exposed fema les (115 kJ/d, body mass = 20 g). This pattern differs from that found in a few species of voles and mice, in which lactating females achiev e higher rates of assimilation than cold-exposed animals. The results do not support the hypothesis that enery budgets of animals are limite d centrally by the rate of energy assimilation from food, irrespective of which metabolic function constitutes the main energy expenditure. The discussion about physiological limits to energy budgets must invol ve information about the life strategies of the animals.