Maternal behaviors of gray whales ( Eschrichtius robustus ) on a summer foraging site

The weaning period for gray whale ( Eschrichtius robustus ) calves is important for maternal instruction and learning. We examined observational and acoustic data from a foraging site for evidence of calf development and mother‐young information transfer. Site survey data demonstrated an initial prioritization of calf protection by using shallow shoreline areas. Foraging in more open water was only noted in late summer, perhaps an indicator of the maturation of the calf. Other indicators of development were found in acoustic recordings made over two summers. Motherese call types have been reported from recordings made in breeding lagoons, but have not before been described outside of calving regions. They were present in recordings from this study site, predominantly in the early summer and not heard past late July. We suggest vocal repertoire may evolve as the calf ages, and more adult calling behaviors eventually replace motherese. Long‐term mark‐recapture analyses demonstrated a high return of calves to the area to forage in summers subsequent to weaning, suggesting maternally inherited prey preference and site use behaviors. From our findings we suggest a calf's first summer is a highly critical period for development and may be formative in shaping future behaviors and habitat use patterns.