NESTBUILDING IN FREE-RANGING DOMESTIC SOWS

Nine nulliparous Yorkshire X Landrace sows were observed continuously during the last 24 h before farrowing in a 12.5 ha semi-natural enclos ure. Seven sows left the normal home ranges about 15-20 h pre-partum a nd wandered on their own seeking nest sites. Four of the sows farrowed on natural sites in the forest, two farrowed in small sheds and three in the larger shed, where the herd spent the nights. The total amount of nesting varied considerably between individuals (range 3.2-32.8% o f observations during the last 24 h). Irrespective of farrowing site, factor analysis showed that gathering and arranging nest material was related to a behavioural factor uncorrelated to other aspects of nestb uilding (e.g. pawing, nosing and rooting). Sows farrowing in sheds had significantly lower frequencies of behaviour belonging to this factor (4.4 vs 16.2% of the observations). Temporal patterns of nesting were similar in all sows. We conclude that nestbuilding in sows depends up on more than one motivational process. Whereas the onset of nesting mo tivation as such is most likely triggered mainly by internal factors, the course of nestbuilding and the material-oriented behaviour strongl y depends on external factors, such as the degree of protection of the nest site and the availability of material.