Researchers might use other hypothesis to study the role of predators in the natural selection process including: 1. Looking at populations. When the prey population goes up does the predators population go up? Or is it the opposite. 2. Camoflauge effecting attacks: Have an animal (reptile) that can change color freely to try and hide from predator. Then have an animal (reptile of the same sub species) who cannot change color to hide from a predator.
Work Step by Step
You can use your imagination somewhat for this question, just keep in mind the level of control necessary to effectively test only your target variables in an experiment and/or considerations for interpretation of observational studies that cannot be completely controlled.