The future of clay model studies

Background: Many intriguing questions about predator-prey interactions can be addressed by using clay models of prey animals. These are placed in the field to test predators' avoidances or preferences (testing e.g. color or shape) or to gain insights into predator identity. Modeling clay allows teeth, beak and jaw marks to remain on the model for identification. First used 30 years ago, clay models are now widely deployed. Ever since, the complexity of hypotheses, modeled species as well as the number of clay models used per study has increased. Although clay models are a valuable research tool, the method has limitations. Some questions cannot be addressed with these experiments, yet there is potential for improvement. Main body: We focus on the following aspects that need attention for clay model studies (CMS) in the future: (1) Use of proper clay materials, (2) how to standardize attack identification, (3) limitations of clay model studies, (4) use of clay models beyond predation experiments and (5) the next generation of clay model studies. Conclusion: We conclude that certain aspects of the clay model paradigm urgently need greater standardization. We advocate the use of harmless clay products and non-toxic inks, as well as having a neutral person to evaluate the marks left in the clay against pre-defined inclusion criteria. Further we suggest to use experimental data more cautiously in respect to evolutionary explanations, to use clay studies in detection experiments and to develop methods for attacker identification based on predator salivary DNA.