The development of intruder attack in colonies of laboratory rats

Most attacks by rat colony members on strange intruders are made by a single dominant male. Such dominance, and the attack behaviors themselves, develop in a relatively fixed sequence over sessions with strange intruders. The entire sequence of attack on intruders occurs earlier in the intruder sessions for older rat colonies than in those for newly established colonies: conversely, more attack is seen in colonies with prior intruder experience than for intruder-naive colonies of equivalent age. Thus both experience within the colony and specific experience with strange intruders influence the rate of development of attack on intruders by dominant colony rats.