Answer
Although both animals have the same mass, the mouse will eventually have a higher metabolic rate. This is because the mouse is an endothermic animal and endotherms exhibit an apparently higher metabolic rate than ectotherms.
Work Step by Step
pg.885 compares the BMR of an alligator (an ectotherm) to the BMR of a human (an endothem) and the human's BMR is significantly higher than the alligator.