Caterpillar traits and predation rates: Using clay models to test hypotheses about organismal structure/function and land use effects on predation

Lab activities using clay caterpillar models to study predation rates have been in use for years as a simple, low-cost method for introducing college and high school students to field studies and experimental design (e.g., Curtis et al. 2013, Leuenberger et al. 2019). The multi-week lab activity described here is a modification of this model system that introduces students to (1) the interacting effects of land use and organismal traits on predation rates and (2) design of a place-based experiment that tests multiple variables. Students work in small groups, or as a class, to develop a hypothesis about how predation rates might vary among caterpillars based on a particular organismal trait (e.g., size, color/pattern, choice of resting location) in two or more different habitats found in their local environment. Each group designs an appropriate experiment and uses nontoxic colored plasticine clay to create caterpillar models, which are built around pipe cleaners and tied to appropriate structures (e.g., small branches). Students retrieve the caterpillar models two weeks later and record predation attempts and, when it can be determined, the likely predator. Students then analyze their data using appropriate inferential statistics, create a figure showing whether their hypothesis was supported, and present their findings to the rest of the class.