The data of Iriarte and colleagues (1990) suggest that prey size may favor a particular body size among pumas (see fig. 7.19). However, this variation in body size also correlates well with latitude; the larger pumas live at high latitudes. Consequently, this variation in body size has been interpreted as the result of selection for efficient temperature regulation. Homeothermic animals are often larger at high latitudes, a pattern called Bergmann's rule. Larger animals, with lower surface area relative to their mass, would be theoretically better at conserving heat. Smaller animals, with higher surface area relative to their mass, would be theoretically better at keeping cool. So what determines predator size? Is predator size determined by climate, predator-prey interactions, or both? Design a study of the influence of the environment on the size of homeothermic predators.