Addressing the behavioral priorities of captive animals and the development of practical, objective measures of the value of environmental resources is a principal objective of animal welfare science. In theory, consumer demand approaches derived from human microeconomics should provide valid measures of the value of environmental resources. In practice, however, a number of empirical and theoretical problems have rendered these measures difficult to interpret in studies with animals. A common approach has been to impose a cost on access to resources and to use time with each resource as a measure of consumption to construct demand curves.This can be recorded easily by automatic means, but in a number of studies, it has been found that animals compensate for increased cost of access with longer visit time. Furthermore, direct observation of the test animals’ behavior has shown that resource interaction is more intense once the animals have overcome higher costs. As a consequence,measures based on time with the resource may underestimate resource consumption at higher access costs, and demand curves derived from these measures may not be a true reflection of the value of different resources. An alternative approach to demand curves is reservation price, which is the maximum price individual animals are prepared to pay to gain access to resources. In studies using this approach, farmed mink (Mustela vison) paid higher prices for food and swimming water than for resources such as tunnels, water bowls, pet toys, and empty compartments. This indicates that the mink placed a higher value on food and swimming water than on other resources.