Choices of laboratory rabbits for individual or group-housing

In group-housed female laboratory rabbits, aggression can occur during, and after, the establishment of dominance hierarchies and in association with sexual behaviours. Low-ranking animals receive more attacks than high-ranking ones. To investigate whether the low-ranking rabbits would avoid the potentially stressful group-pen in favour of a solitary compartment they were given the choice between their group-pen and a solitary pen. In Experiment 1, the solitary pen was of the same size (2.8 m(2)) and contents (straw, boxes, ledges) as the group-pen. Nine low-ranking and nine high-ranking rabbits from nine different groups were tested. In Experiment 2, the solitary pen was smaller (0.56 m(2)) and did not contain straw, boxes or ledges. Only the nine low-ranking rabbits were tested. Each rabbit was tested in 20 trials. After ten trials, the positions of the choice pens were swapped. The rabbits' choices were analysed using binomial tests and loglinear models. In Experiment 1, the low-ranking rabbits showed a preference of 1.7 to 1, the high-ranking rabbits of 1.3 to 1, for the solitary pen. Five out of the 18 tested rabbits showed a significant preference. The effect of social rank on the rabbits' choice was not significant. In Experiment 2, the low-ranking rabbits preferred the group-pen by 5.2 to 1. Eight out of the nine tested rabbits showed a significant preference. Neither the aggression levels within the groups immediately before the trials nor the long-term average aggression level seemed to affect the rabbits' choice. The outcome of the trials depended only on the solitary pen on offer.