Mother-pup vocal recognition in the grey seal (Halichoerus grypus) of Sable Island, Nova Scotia, Canada

Parental recognition of offspring would be expected to evolve among densely populated species in which parental investment is large, and separations o f the mother-pup pair are frequent. Although otariids present a well-develo ped system of mutual vocal recognition, evidence in phocids is weak. Furthe rmore, allo-suckling is prevalent in some species and may reflect confusion over the identity of pups. The vocalizations of grey seal Halichoerus gryp us pups have been found to be stereotyped and individually distinctive on t he Isle of May, Scotland. However, playback experiments showed that mothers fail to discriminate between the vocalizations of their pup and a non-fili al pup. Moreover, widespread allo-suckling was observed. In contrast, grey seals on Sable Island, Nova Scotia, a population reproductively isolated fr om that of the Isle of May, show very little allo-suckling. This may reflec t the presence of a recognition system that does not seem to be present on the Isle of May. During the 1999 breeding season on Sable Island, vocalizat ions of grey seal pups were recorded and playback experiments carried out t o determine whether female grey seals respond differently to the playback o f vocalizations of their own pup, a familiar pup and an unfamiliar pup. Gre y seal mothers were found to make significantly more head turns and body mo vements towards the loudspeaker during the playback of their own pup call t han during the playback of a familiar or unfamiliar pup call. In addition, there was no evidence of an effect of pup age. This suggests that female gr ey seals can discriminate between pup calls using the stereotyped and indiv idually distinctive vocalizations of their pup, and that different selectiv e pressures may be in operation between the Sable Island and Isle of May co lonies.