NEST BUILDING IN DOMESTIC SOWS - THE ROLE OF EXTERNAL STIMULI

To study the role of external stimuli in triggering and controlling nest building, 12 domestic sows, Sus scrofa, were randomly selected for farrowing in one of two environments. Six sows were kept in pens measuring 2.5 × 3 m enriched with a soil bed and a straw rack ('rich' situation), and six were kept in identically shaped pens with no soil or straw ('poor' situation). Their behaviour was videotaped during the 48 h preceding farrowing. No significant differences between the situations were found with regard to the total frequencies of nesting behaviour. The relative frequencies of behaviour patterns mainly performed at the beginning of the nesting period (nosing and rooting) were significantly higher in the poor environment, while those mainly performed later during nesting (carrying material, arranging) were more frequent in the rich environment. No signs of vacuum gathering and carrying and only a few instances of vacuum arranging were recorded in the poor environment. A factor analysis of the behaviour in the rich situation suggested the existence of two different clusters of behaviour patterns, associated with either a 'preparation factor' (standing, nosing and rooting) or a 'nest material factor' (walking, carrying material and arranging). The findings support a model for the control of nesting in sows with a first part of preparation of the nest site, largely triggered by internal factors, and a second part of gathering and arranging nest material, largely dependent on external stimuli. © 1993 The Association for the Study of Animal Behaviour. All rights reserved.