Prevention of stereotypic wire-gnawing in laboratory mice: Effects on behaviour and implications for stereotypy as a...

Three groups of six pairs of adult male laboratory mice of the ICR-strain kept in standard laboratory cages were selectively prevented from stereotypic wire-gnawing for 1, 5 or 10 days, respectively. Behaviour was observed throughout the 12 h dark period one day prior to prevention, on day 1, 4 or 9 (depending on the group) during the period of prevention and on post-inhibitory day 1 and 3. Prior to prevention wire-gnawing was positively correlated (P<0.05) with total activity and climbing. During prevention all three groups showed a significant reduction in total activity (non-stationary; P<0.05) and climbing (P<0.001) and significantly enhanced inactivity (lying motionless; P<0.05). However, the decrease in total activity was positively correlated with base levels of wire-gnawing only on day 1 (P<0.01) but not at later stages of prevention. Similarly, climbing during prevention was positively correlated (P<0.05) with base levels of wire-gnawing on day 1 and 4 but not on day 9 of prevention. These results indicate that the mice only gradually adapted to the new situation. On post-inhibitory day 1 all three groups resumed wire-gnawing at pre-treatment base levels with performance following the same time course throughout the dark period but with significantly reduced peak performance (P<0.05). In the light of motivational theory these results shed doubt on the general validity of the coping hypothesis. Two alternative explanations are discussed.