| Abstract: | The object of the present study was to assess the rat's socioagonistic behavior by means of ethological procedures. Two groups of male Wistar rats were used: 33 residents and 66 intruders. To allow reliable characterization of social and agonistic patterns, social interactions were increased by the isolation of residents and, on the other hand, both offense in residents and defense in intruders were increased by differences in weight, agonistic experience, and habituation to the enclosure. Encounters were videotaped, and the animals' behavior was analyzed by a 27-pattern ethogram and a software package made up to this end. Several patterns parameters were quantified, and two ethological mathematical models were employed: sequential analysis of preferential directions and cluster analysis based on similarities between patterns. Following mean latencies of the most frequent elements, the first four pattern sequences appeared to be the same in both groups of animals. From the fifth pattern on, residents displayed mainly dominance and threat, whereas intruders showed defensive and submissive patterns. Attack was also displayed by residents, but less frequently than dominance and threat. The alpha status was established by two sorts of domination, either through dominance and threat or by attack. The mean frequency of the intraindividual transition of patterns was higher in residents than in intruders. Pathway graphs, derived from sequential analysis, showed some common dyads, triads, or quadrads of patterns, but they basically defined different behavior structures in residents and intruders. Dendrograms, obtained by cluster analysis, allowed classification of patterns into behavior categories. The categories in residents were exploration, dominance, threat, and attack, and they encompassed 18 elements; in intruders the categories were exploration, dominance, and defense, and they consisted of nine patterns. A submissive category composed of three patterns could be also deduced considering similarity results. To summarize, six behavior categories were obtained: one “socioindividual” (exploration) and five “agonistic” (dominance, threat, attack, submission, and defense). In conclusion, the present study shows how ethological procedures may help to elucidate the rat's socioagonistic behavior and to classify the observed patterns into behavior categories. |
