Preferences for limited versus no contact in SD rats

In biomedical research, single housing of rats is used in different test paradigms and the rats are traditionally group-housed prior to testing. Intuitively this separation may have a negative impact on animal welfare. The objective of this study was to assess the importance of non-tactile contact with a social partner. The hypothesis was that rats, previously housed in pairs, prefer non-tactile contact with a partner to single housing. Moreover, it was hypothesized that females show a higher preference for non-tactile contact than males. Animals were housed for 48 h in two-compartment cages, where the animal could choose either to spend time in the compartment, where only a perforated plexiglas wall separated it from its social partner, or to spend time in the compartment with no rat behind the plexiglas barrier. The proportion of time spent in the two compartments was evaluated. We found a significant effect on gender (P = 0.0368) with females spending significantly more time close to the companion animal. During their inactive period, females spent approximately half their time close to their partner, whereas males preferred to stay in the cage next to the empty compartment. Female rats also demonstrated more activity compared with males (P < 0.0001).