Behavioural differences in non-reproductive adult females in a long-term selection experiment for litter size in mice

In a previous study, it has been shown that adult, non-reproductive female mice from a line Ž . Ž . selected for high litter size at birth S-line have higher residual feed intake RFI than females of Ž . a non-selected control line C-line . Several studies have indicated that a higher RFI is related to a higher activity level. Differences in activity may suggest underlying differences in coping strategies. To investigate whether coping strategies have been affected as a correlated effect of selection for high litter size, 48 non-reproductive mature Cand S-line females were twice subjected to an open field, seven times to a maze, once to a social confrontation and twice to a runway test. In the second open-field test, S-line females crossed more squares than C-line females and were less reserved to enter the centre of the open field. In the maze tests, S-line females showed more locomotion activity than C-line females. They encountered dead-ends more often and returned more often to the starting area in the first maze test. No differences were found in their reaction towards an extra-maze cue change. In the social confrontation test, S-line females showed more locomotion activity, were less immobile and investigated the floor and opponent less than C-line females. S-line females ran faster in both runway tests than C-line females. These results suggest that the novelty response of S-line females is more dominated by an active coping style than that of C-line females. However, more tests, such as additional behavioural tests, physiological tests and neurobiological tests are required to be more conclusive on whether ) Corresponding author. Tel.: q47-64948000; fax: q47-64947960; e-mail: [email protected] 0168-1591r00r$ see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0168-1591 99 00092-1 ( ) W.M. Rauw et al.rApplied Animal BehaÕiour Science 66 2000 249–262 250 selection for high litter size has resulted in mice that adopt the active coping strategy. q 2000 Elsevier Science B.V. All rights reserved.