When an animal eats food, its cells transform nutrients, like sugars and fats, into energy. This fuels the body’s metabolism—the many chemical processes needed to sustain life.
For some animals, like mammals and birds, energy produced by their cells during metabolism generates heat. This helps regulate their internal temperature (see Heat Regulators). These animals are endothermic, or warm-blooded. They differ from reptiles, fish, and amphibians, which are ectothermic, or coldblooded. These critters rely on the temperature of their environment to maintain their internal body temperatures.
Scientists have long known that aquatic mammals have revved-up metabolisms that help maintain their internal temperatures in frigid waters. In fact, a sea otters’ metabolism is three times greater than would be expected of an animal their size. But no one knew how that mechanism worked or whether it was the reason sea otters could sustain their temperatures. That led Wright to take a deeper look at what was going on inside sea otters’ cells.