Behavioral profiles of genetically selected aggressive and nonaggressive male wild house mice in two anxiety tests

Artificially selected aggressive (SAL) and non-aggressive (LAL) male house mice were tested in a hexagonal tunnel maze and light-dark preference (LD) box to determine if the bidirectional selection for aggressive behavior lea ds to a coselection for different levels of trait anxiety. The tunnel maze consists of an open, brightly lit central arena surrounded by a complex sys tem of interconnecting tunnels. As in the LD box, animals which spend less time and are less active in the brightly illuminated section of the maze ar e considered to have higher anxiety levels. In the tunnel maze, the LAL mic e showed more exploration and spent more time in the central arena than the SAL animals, but only during the final 2 min of the 6-min test. This reduc ed preference for the central arena was not due to general inactivity or a failure of the SAL to find the central arena and indicates a higher level o f state anxiety in the aggressive animals. In contrast, no "anxiety-like" d ifferences were found in the LD box, either for the percentage of time spen t in the light compartment or for the number of crossings. SAL mates actual ly showed higher levels of moving and rearing, and lower levels of freezing , than did LAL males.