climates First of all we need to understand what ectothermic and endothermic animals are. Animals differ in their abilities to regulate body temperature (thermoregulation). We sometimes use the terms "cold-blooded" or "warm-blooded." Most reptiles feel cold to the touch, while mammals and birds often feel warm. Somewhat more precise descriptions can be made by using the terms poikilothermic and homoiothermic. The body temperature of poikllotherms is relatively variable, while that of homeotherms is relatively constant. Even more useful terms ....