Social rank and priority of access to resources in domestic fowl

Abstract

One of the most frequently encountered assertions concerning the concept of social dominance is that high rank confers priority of access to resources. There have been few systematic studies to document the reliability of this relationship. We report a recent study in which the hypothesis of close linkage between social rank and access to resources was tested. Five-bird single-sex flocks of domestic fowl representing four different stocks were observed for (1) determination of rank order among flock members, and (2) the frequency and duration of time each member had control of resources provided such that only a single bird would have access to a resource at any given time. These resources were feed, water, perch, nest box and dust-bathing litter box. The results of this study were: (1) competition among flockmates was manifest only at the feeder, (2) a significant overall relationship between social rank and frequency and duration of feeding was obtained, (3) within individual flocks, the higher ranking birds tended to have higher feeding measures, but in few flocks was the measure of rank congruent to the measure of feeding. In the most extreme case, both male and female flocks of one stock had a five-rank linear dominance hierarchy; in these flocks the 'feeding rank order' consisted of two tiers, with no feeding score differences among the top three socially-ranked birds and none between the two bottom social ranks. A second experiment tested the hypothesis that in flocks of five birds with a stable dominance hierarchy, no differences would appear in the expression of aggressive behavior directed to an introduced stranger (i.e. the 'control animal' hypothesis was tested). The results of this experiment were: in none of the five replicates did the alpha bird contribute the highest proportion of aggressive acts to introduced strangers. Second, third and fourth rankers showed highest scores depending on the flock. In domestic fowl, the alpha bird clearly does not have the 'control animal' role with respect to external sources of disturbance. Statements implying close linkage between social rank established by aggression and various global constructs such as priority of access to resources and defense of the group must be scrutinized with care.