EVIDENCE OF PRE-MATING REPRODUCTIVE ISOLATION IN 2 POPULATIONS OF THEVLEI RAT OTOMYS IRRORATUS - EXPERIMENTS OF INTRAPOPULATION AND INTERPOPULATION MALE-FEMALE ENCOUNTERS

Studied was the male-female interaction of representatives of two allo patric Otomys irroratus populations (Kamberg and Karkloof) in 40 intra population and 34 interpopulation encounters. The study aimed to: (1) establish the existence of population-specific courtship behaviour dur ing intrapopulation encounters; and (2) ascertain whether or not diffe rences in courtship behaviour rendered males and females incompatible during interpopulation encounters. During intrapopulation encounters, Kamberg males and females were less aggressive and more amicable than their Karkloof counterparts, and Karkloof males performed more sexual acts than Kamberg males. These behavioural differences apparently refl ect the social organization and mating behaviour of each population. C ompared to intrapopulation pairings, interpopulation pairings displaye d more exploratory behaviour, fewer sexual acts, more aggression, less amicability, and later development of essentially amicable interactio n. It is possible that population-specific olfactory, visual and tacti le cues resulted in highly aggressive interpopulation encounters Aggre ssion may function as a pre-mating reproductive isolating mechanism be tween the Kamberg and Karkloof populations should they meet in nature.