BEHAVIORAL DISCRIMINATION AMONG CHROMOSOMAL RACES OF THE HOUSE MOUSE (MUS-MUSCULUS-DOMESTICUS)

This work is concerned with the extent of behavioural discrimination b etween three chromosomal races of the house mouse (the standard 40-chr omosome race and a 32- and 36-chromosome races) found in the vicinity of a hybrid zone in northern Scotland. Mice were investigated for seve ral elements of their social behaviour. Within-population dyadic encou nters did not show consistent behavioural differences attributable to karyotype among five populations (two standard race, two 36-chromosome race, one 32-chromosome race). Between-population dyadic encounters r evealed significant differences between three populations. The standar d population examined appeared to be the most ''open'' to foreigners, the 32-chromosome population the most ''closed'' while the 36-chromoso me mice displayed an intermediate response. Differences in behaviour d isplayed during between-population as compared to within-population dy adic encounters revealed the occurrence of behavioural discrimination between populations. The implication of these results on the dynamics of the hybrid zone are discussed.