Department of Animal Physiology, University of Groningen, Haren, The Netherlands
Many animal species live by nature in rather complex social structures. Several studies in group-housed rats show that the incidence of certain forms of stress pathology, such as hypertension and immune deficiencies, are related to the position of the animal in the social hierarchy and its stability. So far, the study of this intriguing relationship has been seriously hampered due to the technical limitations of recording behaviour and physiology in social groups of animals. The present paper will report on a project aimed at solving these technical issues in a colony of male rats. A colony cage of four square metres is used in which five male and five female wild type rats are housed permanently. The colour tracking option of EthoVision (Noldus) is used for monitoring the spatial relationships between the male members of the colony. A statistical analysis of the asymmetry of these spatial relationships will be used as an index of the social structure of the group. Animals are individually marked using fluorescent dye. Special emphasis is given to an independent validation of the parameters obtained with the colour tracking system. This will be achieved by a comparison of data obtained by direct ethological observation of social interactions in the colony with the data obtained by EthoVision.
For physiological recordings, each male colony member is equipped with an ECG, temperature and activity transmitter (DataQuest). The colony cage is provided with a special receiver system allowing a continuous recording of the transmitter signals over the whole range of the colony. The first preliminary results will be presented.
Ultimately, the colony will be provided with a system allowing the continuous recording of food and water intake in individual animals as well.