Theoretical models, assuming an underlying conflict of interest between parents and offspring, suggest that begging can be an honest signal of offspring need provided that it is costly. Models on begging have been tested primarily on those birds in which parents provide care for several offspring. For these species, the underlying conflict selecting for extravagant (and apparently costly) begging displays might be sibling competition rather than parent-offspring conflict. We tested hypotheses on begging and parent-offspring conflict with the grey seal, Halichoerus grypus, as our model species, in which lactating females care for a single pup. As predicted from models of begging as an honest signal of need, pups begged at a significantly higher rate when hungry than when satiated. Furthermore, a mother was more likely to approach her pup shortly after the pup had uttered a begging call than within a randomly chosen period. We found no consistent support, however, for the assumption that there are strong conflicts of interest between mothers and pups. For example, the rate of suckling was not correlated with begging rate, suckling bouts terminated by pups were not longer than those terminated by mothers, and, although pups initiated the majority of suckling bouts, mothers did not terminate more suckling bouts than pups. These findings thus suggest that begging in species that care for a single offspring may evolve in the absence of strong parent-offspring conflict. © 2001 The Association for the Study of Animal Behaviour.