The marginal value theorem refers to an economic concept that states that an animal will leave a resource patch once the marginal gain (the additional value) they receive from staying is less than the gain they could receive from moving to a new patch. Alternatives to this term include the interpretation of patch use theory and optimal foraging theory. In behavioral ecology, this concept is referred to as the giving-up density theory or quitting harvest rates. Regardless of the name used, this theory helps to explain how animals balance the costs and benefits of exploiting resources and how they optimize their foraging behavior to maximize their fitness.