In colonial mammals, individual voice recognition between mother and offspring is a key factor for mother-pup reunions among numerous other individuals. The pup's ability to recognise its mother's voice is crucial for its survival: in most species, except phocids, females only feed their offspring and reject any attempt of milk stealing by strange pups. In the subantarctic fur seal Arctocephalus tropicalis, females have to leave their newborn a few days after birth to feed at sea. Pups recognise their mother by voice when she comes back from the sea. We investigate at what age a fur seal young is able to respond specifically to its mother's voice. Using playback experiments, we show that the subantarctic fur seal pup needs to be two to five days old in order to develop recognition of the mother's voice. Through investigating the relationship between the mother departure date and the duration of the young's learning process, we show that the mother delays her departure for her first feeding sea-trip until her pup responds specifically to her calls. In spite of the strong energetic constraints which may encourage her to go to sea as soon as possible after parturition, a mother leaves her offspring only when it is able to recognise her voice.