Forests are excellent “outdoor classrooms” for active learning in ecology and evolution; however, in many areas trees have no leaves or visible animal activity for much of the year. Fallen leaves may preserve evidence of interactions such as herbivory and infectious diseases, although these can be difficult to differentiate from mechanical damage and decomposition in older fallen leaves. I developed an exercise in which students collect fallen leaves and observe several different types of damage to the leaves. I provide images and descriptions of different types of damage and practices to differentiate them. In addition, I provide a list of questions that can be answered by collecting fallen leaves and observations of damage. My students gained valuable quantitative literacy skills by entering data into an online worksheet and performing various calculations and data analysis techniques. This exercise provides many benefits and can be an engaging addition to a high school's or college's outdoor curriculum outside of the growing season.