Subordinates explore but dominants profit: resource competition in high Arctic barnacle goose flocks

Social dominance plays an important role in assessing and obtaining access to patchy or scarce food sources in group-foraging herbivores. We investiga ted the foraging strategies of individuals with respect to their social pos ition in the group in a flock of nonbreeding, moulting barnacle geese, Bran ta leucopsis, on high Arctic Spitsbergen. We first determined the dominance rank of individually marked birds. The dominance of an individual was best described by its age and its sex-specific body mass. Mating status explain ed the large variation in dominance among younger birds, as unpaired yearli ngs ranked lowest. In an artificially created, competitive situation, subor dinate individuals occupied explorative front positions in the flock and-we re the first to-find sites with experimentally enriched vegetation. Neverth eless, they were displaced quickly from these favourable sites by more domi nant geese which were able to monopolize them. The enhanced sites were subs equently visited preferentially by individuals that succeeded in feeding th ere when the exclosures were first opened. Data on walking speed of foragin g individuals and nearest-neighbour distances in the group suggest that sub ordinates try to compensate for a lower energy intake by exploring and by l engthening the foraging bout. Observations of our focal birds during the fo llowing breeding season revealed that females that returned to the study ar ea were significantly more dominant in the previous year than those not see n in the area again. (C) 2001 The Association for the Study of Animal Behav iour.