DEFENSIVE ASPECTS OF BURROWING BEHAVIOR IN RATS (RATTUS-NORVEGICUS) - A DESCRIPTIVE AND CORRELATIONAL STUDY

Several burrowing behavioral characteristics of five different, genetically-biased, strains of rats (Rattus norvegicus), with each showing various defensive and open-field behaviors, were investigated to examine the defensive aspects of burrowing behavior. The strains used were the Tsukuba High- and Low-Emotional (THE and TLE), F344/DuCrj (F344), Long Evans (LE), and the Wistar-lmamichi/lar (WI). The THE and LE strains showed significantly shorter burrowing latency, more digging activity, and longer length burrows, with most rats escaping into their burrows at a loud crash sound. On the other hand, the TLE and WI stains displayed significantly longer burrowing latency, less digging activity, and shorter length burrows, with only a few rats escaping. These findings showed the consistency among the burrowing characteristics and a close relationship between burrowing and escape. The F344 strain, on the contrary, showed a shorter burrowing latency and more digging activity than the TLE and WI strains (although similar length burrows), yet few rats escaped. Digging, burying, open-field defecation, and re-emergence latency after escape correlated highly with each other, possibly suggesting their defensive nature. In conclusion, it is possible that burrowing behavior is a species-specific defense reaction (SSDR), yet factors involved in burrowing seem to be complicated, with more extensive studies therefore required.