Agonistic behavior, the development of the social hierarchy and stress in genetically diverse flocks of chickens.

The agonistic behavior and development of the social hierarchy of juvenile pullets were studied in two lines of chickens which had been divergently selected for juvenile body weight and in which the dwarf gene (dw) was segregating. The lines differed significantly in both the frequency and intensity of agonistic encounters. Dwarf and normal genotypes differed in the frequency of encounters in both lines, whereas for the intensity of encounters, the difference was only in the high weight line. Although the frequency was more important than the intensity of encounters in determining social rank, agonistic behaviors accounted for only 20% of the variation in rank. The stability of the social orders increased slightly between 6 and 10 weeks of age. Although the correlations between behavioral and physiological variables agreed in sign with those predicted of stressors, their values were low. Therefore, it was concluded that the pullets were only minimally stressed by normal agonistic activity during the development of the social hierarchy.