The pig is unique in the way that it gives birth to a large number of newborns in each litter. Because of this the sow has developed a special behaviour during suckling to ensure that not only a part of the litter gets all the milk. Milk is only available during milk letdown. The piglets have to massage the udder for a long time before letdown and the more piglets at the udder the sooner the milk comes. The sow has developed a special grunting pattern to let the piglets know when she is ready for suckling and to signal milk letdown. Our aim with this study was to investigate if sows have individual grunting patterns repeated over time. We also wanted to know if sows with a more distinct grunting pattern have better growth in their litters.