We examined the skulls of Arctocephalus australis, Callorhinus ursinus and Otaria byronia with the objectives of (1) estimating the development and growth rates and comparing these parameters among the species; (2) describing the development for each linear measure, for each species and sex; (3) determining which variables are best correlated with age; (4) determining age of physical maturity. We employed traditional and geometric morphometric techniques to study the skulls. In A. australis and C. ursinus, skulls of females mature at about 6 years of age, and those of males at about 8 years. Otaria byronia matures later, at about 9 years. Using geometric morphometric data sets, the rate and constant of growth in A. australis did not differ between the sexes. Callorhinus ursinus and O. byronia showed rates significantly different between sexes concerning growth (and in the constant as well), but only O. byronia differed between sexes in both developmental model parameters (rates and constant). Comparisons between the growth and developmental models showed significant differences in slope and constant. In both treatments employed, a relationship between size and shape dimorphism could be inferred for the skulls of all three species. We conclude that rates or timing of growth and development evolves within a conserved spatiotemporal organization of morphogenesis.

New Zealand fur seals (Arctocephalus forsteri) forage mostly in open waters at night and spend parts of the day in coastal sheltered sites, where they may play, rest and eliminate wastes. We recorded the purple wrasse (Notolabrus fucicola) feeding on faeces and vomits of these pinnipeds at Fortescue Bay in the Tasman Peninsula, Australia. This behaviour allows the wrasse to get nutrients from open waters that otherwise would not be available. Thus, it is suggested that the fur seals have the role of transferring nutrients from open waters to inshore reefs and provide them as particulate food to fish. This functional role is apparently recorded for only one species of marine mammal so far, the spinner dolphin (Stenella longirostris), in tropical oceanic waters.