Why Do Animals Eat the Bark and Wood of Trees and Shrubs?

The most consummate wood feeders are the billions of termites throughout the world that literally devour thousands of tons of woody debris every year in forests as well as lumber in buildings. Many of our most serious and damaging insect pests are the bark beetles and wood borers that feed on the parts of trees for which they are named. Even mammals ranging in size from mice to elephants consume bark and woody branches. They all have specialized digestive systems that allow them to extract nourishment from this material, something humans cannot do. To understand how bark and wood can serve as food for these critters requires knowledge of cell wall structure, bark and wood anatomy, movement and storage of food in trees, and the variations in digestive systems among animals.