A note on instability of the dominance hierarchy and variations in level of aggression within groups of fattening pigs

Abstract

SUMMARY Social organization in the pig is based on the dominance hierarchy. Hitherto this has been assumed to be stable but present studies have shown that spontaneous changes of rank can occur. It has proved almost impossible, however, to alter social ranks artificially. Pig groups also show considerable fluctuations from day to day in the level of aggression at feeding periods. This variation cannot be correlated with the occurrence of sexual cycles in the females or variations in the general level of group activity.