Physiology

Three new studies show that most adults have unexpectedly large and active deposits of a calorie-burning type of fat that biologists once thought disappeared after infancy. The persistence of brown fat suggests a potential new strategy to fight obesity, which is epidemic in the United States and increasing rapidly in the developing world.

The toucan's enlarged bill may not just be for attracting mates or handling food, as biologists have speculated. It also may be able to exchange heat with its environment, enabling the bird to adjust its body temperature as its surroundings change.