there are a few general principles of normative models (or bayesian models) that lend them to be useful for ethology.
we assume that animals are trying to be most efficient to solve a task in the sense that evolution has helped constrain the behaviors to be close to optimal. this helps us understand mathematically and predict for future behavior. A good fitting model to actual behavior will predict behavior in new environments or situations.
normative models are structured about behavior and so they tell us what is important to look at about the behavior in a given environment — important for predicting behavior.