TETRADIC ENCOUNTERS OF WISTAR RATS (RATTUS-NORVEGICUS) AFTER SOCIAL DEPRIVATION - INDIVIDUAL BEHAVIORAL FEATURES

In young but adult male Wistar rats the individual behavioural interactions during tetradic encounters in the open field were studied after three weeks of differential housing. The purpose was to look for social roles within the tetrade an to investigate the influence of social deprivation on interindividual differentiation. Behavioural features of each individual were established according to the time budget of the behaviour, locomotor and spatial parameters, and the recipience of social interactions by the other members of the tetrade. The most ralible feature during repeated encounters was social recipience which revealed significant positive inter-session correlations in group housed (G), contact housed (C), and individually housed (LI) rats. Among the housing groups the highest level of inter-session correspondence concerning nearly all the features was found in C individuals. The existence of social roles was suggested by interfeature correlation analyses. “Clusters” of significantly correlating features were detected which revealed both correspondences and differences between the housing groups. Each social role was characterized by a particular cluster; three of such roles were established: social activity, social attractivity, and exploration of the environment. The latter cluster and its attributed role was only present in non-deprived rats (G). Social activity was characterized by high levels of play and social investigation, and proximity to conspecifics whereas social attractivity was expressed by social recipience positively correlating to the performance of aggression and aggressive play. In LI individuals a discrimination between attractive and non-attractive animals developed some three minutes after the start of the encounter. Socially active rats preferred the proximity of attractive ones and tended to perform the same type of behaviour which the attractive one had shown during the last 30 seconds. C rats behaved in a similar way but a moderate inter-individual differentiation was detected already during the first minutes. In G role-specific differences were poorly expressed. In particular the behaviour of the active rat was less directed and related to the attractive animal. It is discussed to what extent social dominance expressing itself in playful interactions and social attractivity rather than in agonistic fight may be characteristic for establishing groups with an increasing degree of individual recognition. © 1990, Brill. All rights reserved.