Social Rank and Food Access in Red Deer Stags

Abstract

AbstractThe behaviour of a free-living group of male red deer (Cervus elaphus L.) on the Isle of Rhum, Scotland, was studied throughout the year to investigate the relations between social dominance and food access. The study is based on the collection of agonistic interactions between members of the study group outside the rutting season. Analysis of these confirmed that dyadic dominance relationships summate to a very clear agonistic hierarchy, while seasonal changes in frequency and type of interactions suggested that rank in the hierarchy may affect access to food through direct feeding interference. This would constitute a selective advantage of the acquisition of high rank. A behaviour pattern in which a stag displaces a subordinate and takes over his feeding-site is proposed as a mechanism of direct feeding interference. It occurs throughout the year, but with a frequency closely related to changes in food availability and quality. The proportion of such interactions that an individual wins is related to his rank, so advantages gained from this behaviour would primarily benefit high-ranking stags. These are likely to consist of improved body condition and winter survival. The importance of high rank in obtaining access to limited food was supported by the results of a simple experiment providing a small area of fertilized grass. Most of the grazing in the area was due to the highest-ranking stag present at any time.