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Vocalization
Like most otariids, Steller sea lions are vocal in air. Mature male sea lions have a range of vocalizations as part of their territorial behaviors, including belches, growls, snorts, and hisses that serve as warnings to others. Both males and females also produce underwater noises similar to their above water sounds, described as clicks, barks, and belches.

Vocalizations are critical to mother-pup pairs, as the mothers must find their pups in a crowded breeding area when they return from foraging. The mother and pup both use distinctive calls, like names, to help differentiate themselves among the crowd of other sea lions. Their aerial vocalizations have been described as similar to the bleats of sheep, and bellows.

Because Steller sea lions are sexually dimorphic in size, their hearing differs in sensitivity, like due to differences in size of the hearing structures. Females have a higher sensitivity than males, perhaps to hear the higher frequency calls of their pups. The Steller sea lion's hearing range also suggests that they are capable of hearing the underwater calls of one of their main predators, the killer whale Orcinus orca.

Reproductive behavior and life history
Nutritional stress in the 1980s is the likely cause of the decline in number of pups born and the increase in pup mortality. Adult Steller sea lions decreased in body size, but it was most apparent in juveniles, who appeared to be growing at a slower rate thanks to the lack of nutrition.