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Vocal Communication in Pigs: Who are Nursing Piglets Screaming at?


Corresponding author: M. Appleby, Institute of Ecology and Resource Management, University of Edinburgh, West Mains Road, Edinburgh EH9 3JG, UK. E-mail:


Vocalizations during competition among nursing piglets were studied to investigate their possible effects, functions and implications for welfare. In Expt 1, two experimental piglets in each of 14 litters were temporarily deprived of milk by covering their preferred teats on the sow’s udder. These piglets spent more time away from their teats than two control piglets, and vocalized frequently in the 2 min before milk ejection. Frequency of vocalization showed no consistent change over time within nursings; nor did it change in successive nursings despite the fact that hunger presumably increased. In Expt 2, tape recordings of intense vocalizations (screams) produced by piglets competing at the udder were played to 22 litters while they were nursing; each litter was played its own recording, a recording from another litter and silence as a control. Of 51 nursings analysed, 14 were terminated without milk ejection, all during playbacks. When the sow did nurse successfully during a playback, nursing was shorter (138 s) than during the silent controls (179 s). Both these responses by the sow might be expected to advance the next nursing. Piglets rarely showed any apparent response to screaming either from their littermates or from the loudspeaker. These results suggest that the calls function mainly as a signal to the sow that some piglets are being excluded from the current nursing episode.