Abstract
We have investigated ways of measuring captive animals' demands for resources in their environment in order to assess their welfare. In these experiments, the animals have to make an effort to earn a reward (resource), and we quantify their reaction when it is harder to get a reward. Operant conditioning has been used as the method of providing animals with a means of earning a reward, and a second reinforcer has been used as the reward in some cases. However, it is important to pay attention to some factors involved in this method. How to give animals a means of earning a reward and how long they can maintain contact with a reward have an influence on their responses. Moreover, animals' demands for the reward depend on whether or not they can get the reward outside an experimental condition. There are four ways to quantify animal's demand (elasticity of demand, consumer surplus, maximum price paid, and total expenditure), and, if possible, it is recommended that these should be used together. In assessing animal welfare, it is important to correctly set up the experimental conditions.
