FOOD SELECTION IN AN HERBIVOROUS RODENT - BALANCING NUTRITION WITH THERMOREGULATION

The degu, Octodon degus (Rodentia, Octodontidae) is a diurnal herbivor e inhabiting the semiarid and mediterranean environments of northern a nd central Chile. In the field, degus are constrained to specific fora ging areas, mainly by their limited thermal tolerance and by environme ntal food quality. Consequently, we hypothesized that degus must balan ce their diet selection by maximizing nutrients/digestible energy inta ke, in the face of their time and digestive constraints and seasonal/s patial changes in food quality; and by minimizing thermoregulatory ris k, in the face of their low evaporative water loss and seasonal/spatia l changes in environmental temperatures among foraging areas. This hyp othesis was tested in a series of diet selection experiments conducted in an experimental arena, as well as in nutritional trials, involving synthetic diets with different fiber content and thermal patches. As predicted, results of the arena food selection experiments, as well as the nutritional trials, demonstrated that O. degus prefers items of l ow-fiber composition. However, food selection is compromised by season al and spatial changes in food quality and environmental temperatures, coupled with feeding time and digestive and thermoregulatory constrai nts.