EFFECT OF AMBIENT-TEMPERATURE AND ENERGY DEMANDS ON DIGESTIVE FUNCTIONS IN LEAF-EARED MICE (PHYLLOTIS-DARWINI) FROM CENTRAL CHILE

The leaf-eared mouse, Phyllotis darwini, is a nocturnal rodent inhabit ing the semiarid and Mediterranean habitats of northern and central Ch ile. Previous observations suggested that in the field, individuals ma y change food intake according to seasonal changes in ambient temperat ure. We therefore anticipated that P. darwini should increase food int ake in response to lower ambient temperature. As predicted, results of food trials and digestive measurements demonstrated that P. darwini i ncreases food intake and assimilation at lower ambient temperatures bu t does not increase food mean retention time. At lower ambient tempera tures, individuals increase digestive tract size thus improving body m ass maintenance and perhaps survival during winter.