Behavioural variation in two populations of root voles

Significant morphological and physiological variations between root vole Mi crotus oeconomus (Pallas, 1776) populations have been found. Behavioural di fferences between two geographically separated populations were found in th is study. Ultrasonic vocalization and behavioural interaction (non-aggressi ve and aggressive approaches) were monitored during 10-min encounters. Ultr asounds were monitored during encounters involving all possible combination s of males and females of two populations, called here southern (Prague, Cz ech Republic) and northern (Bialowieza, Poland). The northern male-male com bination did not produce ultrasounds. In both populations, males exhibited more aggressive behaviour than females did. Since M. oeconomus females are highly territorial and the home ranges of males overlap, the agonistic beha viour of males may enable them to control a larger area with greater number s of receptive females. We also found significant differences in behavioura l activity between the two investigated populations: southern M. oeconomus showed higher activity than northern root voles did. Separate populations w hich differ morphologically and behaviourally have much to tell us about sp eciation processes. Behavioural divergence can lead to reproductive isolati on and thus create separate gene pools.