Animal economics: assessing the motivation of female laboratory rabbits to reach a platform, social contact and food

We used novel techniques for assessing resource value to investigate what additions to a barren cage female laboratory rabbits, Oryctolagus cuniculus, value. We tested motivation to reach two resources that are potentially practical enrichments: a platform (providing a partly enclosed space and a raised area) and limited social contact with another rabbit through wire mesh and compared these to food and an empty space. To reach these resources, rabbits had to pay entry costs (pushing through weighted doors) which increased every 2 days. With rising costs, rabbits generally rescheduled their behaviour, often reducing visit number and increasing visit length. Measures from economics and behavioural ecology ranked the relative importance of resources similarly (food >= social contact >= platform > empty cage). 'Travel cost consumer surplus' (the area under a demand curve of price versus number of visits) ranked food and social contact similarly, but higher than the platform; 'aggregate consumer surplus' (the area under a plot of weight against the number of rabbits paying each price level for the resource) placed food higher than both social contact and the platform; 'reservation price' (maximum weight pushed) did not discriminate between the three resources; and 'expenditure rate' (weight x visits/days) again ranked food and social contact similarly, but higher than the platform. Overall, rabbits' motivation for access to limited social contact thus came close to that for food, suggesting that they value this highly. Rabbits were almost as strongly motivated to be near a platform, but rarely used it, suggesting it might serve a 'bolt hole' function.