Behavioural biology of the collared lemming Dicrostonyx groenlandicus (Traill): I. Agonistic behaviour

Abstract

1. 1. Agonistic behaviour displayed by male collared lemmings, Dicrostonyx groenlandicus (Traill), was studied by means of observations of paired encounters in a neutral arena. Cinematography was employed in order to facilitate a structural analysis of the behaviour. 2. 2. Eleven major components of agonistic behaviour were described and recorded quantitatively. The recording system allowed both the duration and frequency of components to be recorded and the sequential nature of these events to be investigated. 3. 3. Fighting invariably occurred following brief investigatory activity. Aggressive responses were evoked rapidly, but the cues eliciting attack are unknown. Actual time spent in aggression was small, and injuries of a serious nature were rare. The incidence of vigorous fighting typically decreased with time, indicating some degree of tolerance for the opponent. 4. 4. Little evidence of any rigid timing in the display of acts and postures was obtained. It was suggested that the observed variability in display durations reflected the dependence upon the opponent's behaviour. 5. 5. Significant differences between combatants in the frequencies of chase and attack displays were employed as criteria for the existence of dominance-subordination relationships. Such relationships were demonstrable in 12 of 21 recorded contests. Large interindividual variation in aggressiveness was observed, although rarely were both animals extremely aggressive. It was postulated that the extreme passivity of certain animals had an inhibitory effect on aggression in their opponents. Other factors with possible influence on individual aggressiveness are discussed. 6. 6. Relationships between agonistic components were investigated by means of an analysis of their distribution in time. Certain two-act sequences occurred with frequencies significantly greater than expected, indicating affinity between approach and retreat, defensive and retreat, and between offensive and the acts approach, groom, boxing and chase. Contrary to this, a negative association existed between offensive and retreat, and between displays of offensive, defensive and retreat. 7. 7. Communication between animals was evident from the significant changes in the opponent's behaviour which followed the display of various agonistic components. Certain acts and postures had consistent effects on the opponent's actions. Retreat was followed by approach or chase but not by retreat, offensive, defensive or boxing. Approach and mount led to retreat by the opponent, and boxing was followed by offensive. Offensive and defensive postures led to each other, but not to themselves. 8. 8. It was found that an animal's behaviour at any time is partly determined by the opponent's antecedent display, although dependencies of a higher order may exist. Present behaviour is also influenced by the individual's preceding action, indicating that the context in which the opponent's display occurs is of importance in determining the individual's response.