Summary 1.The science of nutritional ecology spans a wide range of fields, including ecology, nutrition, behaviour, morphology, physiology, life history and evolutionary biology. But does nutritional ecology have a unique theoretical framework and research program and thus qualify as a field of research in its own right? 2. We suggest that the distinctive feature of nutritional ecology is its integrative nature, and that the field would benefit from more attention to formalizing a theoretical and quantitative framework for developing this. 3. Such a framework, we propose, should satisfy three minimal requirements: it should be nutritionally explicit, organismally explicit, and ecologically explicit. 4. We evaluate against these criteria four existing frameworks (Optimal Foraging Theory, Classical Insect Nutritional Ecology, the Geometric Framework for nutrition, and Ecological Stoichiometry), and conclude that each needs development with respect to at least one criterion. 5. We end with an initial attempt at assessing the expansion of our own contribution, the Geometric Framework, to better satisfy the criterion of ecological explicitness.

Many herbivores and omnivores adjust their food selection behavior to regulate the intake of multiple nutrients. Carnivores, however, are generally assumed to optimize the rate of prey capture rather than select prey according to nutrient composition. We showed experimentally that invertebrate predators can forage selectively for protein and lipids to redress specific nutritional imbalances. This selection can take place at different stages of prey handling: The predator may select among foods of different nutritional composition, eat more of a prey if it is rich in nutrients that the predator is deficient in, or extract specific nutrients from a single prey item.