INDIVIDUAL VARIATION IN NURSING VOCALIZATIONS OF HAWAIIAN MONK SEAL PUPS, MONACHUS-SCHAUINSLANDI (PHOCIDAE, PINNIPEDIA), AND LACK OF MATERNAL RECOGNITION

Vocalizations of individual Hawaiian monk seal pups, Monachus schauins landi, do not have unique attributes that enable females to recognize their own offspring. Despite low aggregation density during pupping, a ggressive encounters are common between females with pups. Fostering i s prevalent and may reflect confusion over the identity of pups follow ing aggressive encounters between females. All pup vocalizations were simple in structure and contained true harmonics. The coefficients of variation revealed considerable variance in vocalization structure wit hin pups. Controlling for age, multivariate analyses of variance revea led significant. differences among pups in vocalization attributes. Si gnificant developmental changes occurred in vocalization structure for some pups but not for others. Discriminant function analysis suggeste d that it would be difficult for females to distinguish between the vo calizations of pups. The results of experiments conducted in the field showed that females did not discriminate between filial and alien pup s by voice. In addition, females tended not to foster pups that had vo calizations similar to those of their own offspring. Thus, females see m to be unable to recognize their pups by voice. The apparent lack of vocal recognition of pups may contribute to the high frequency of fost ering in this species.