In some nursings, piglets initiate nose contacts with their mother and emit typical 'croaking' vocalizations. We examined whether the croaking vocalizations reflect the condition of the piglets and whether the sows increase their maternal investments in response to those vocalizations. The following predictions were tested: (i) Piglets with lower weight gain should vocalize more than piglets with higher weight gain; (ii) piglets' milk intake is lower in those nursings in which they vocalize after milk ejection; (iii) piglets make more croaking vocalization in nursings which were preceded by longer intervals since the last nursing with milk ejection; (iv) sows permit longer post-ejection massage in nursings in which piglets vocalized immediately after milk ejection; (v) sows decrease the interval until the succeeding nursing after those nursings in which the piglets have vocalized. Hypotheses (i) and (ii) were investigated by controlling the inter-nursing intervals in 14 sows and recording the milk intake of individual piglets' over 24 hours during days 7 or 8 post partum (Experiment 1). Hypotheses (iii) to (v) were examined through analysing video recordings of undisturbed six h nursing sequences in 29 sows (Experiments 2 and 3). The majority of our predictions were not confirmed: piglets did not vocalize more (either before or after milk ejection) after longer intervals since last milk ejection; they did not vocalize more in nursing in which they received less milk; and it was not the piglets or the litter with a lower milk intake or lower weightgain that emitted more vocalization. Neither of our predictions regarding the influence of croaking vocalizations on maternal investment was confirmed. The vocalizations were in no way associated with the length of the following inter-nursing interval or with the permission of longer udder massage. To conclude, piglet croaking vocalizations during nursings are not reliable indicators of piglet condition and are not used by sows to adjust their maternal investment.