Limits to the Energy Budget in a Rodent, Peromyscus maniculatus: The Central Limitation Hypothesis

The maximum rate of energy assimilation in lactating Peromyscus maniculatus (100 kJ/d, body mass = 25 g) was lower than in cold-exposed females (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 achieve higher rates of assimilation than cold-exposed animals. The results do not support the hypothesis that energy budgets of animals are limited 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 involve information about the life strategies of the animals.