An ethological analysis of open-field behaviour in chickens

Abstract

Two salient but previously unacknowledged aspects of open-field testing involve contact with a potential predator, as a consequence of placement in the open field by a human, and separation from imprinted companions. As a result we propose that open-field behaviour in chickens ( Gallus gallus) represents a compromise between opposing tendencies to reinstate contact with conspecifics and minimize detection in the face of possible predation. Five experiments were conducted to test various implications of this model. Manipulations designed to enhance the predatory overtones of open-field testing were found to postpone reinstatement behaviours (e.g. distress calling and escape attempts) and prolong behaviours that serve to minimize detection (e.g freezing). Unlike the more traditional view of open-field behaviour as an index of general emotionality, our model suggests that the principal reason for movement is based on attempts to reinstate social contact. In support of the model, birds tested in the presence of cagemates showed significantly longer durations of freezing than those tested individually. The same was true for birds maintained in social isolation for two days prior to testing. The applicability of this approach to conceptualizing the behaviour of chickens in the open field is discussed, and the supposed relationship between fear and distress calling is critically evaluated.