Maternal and pup growth strategies of sympatric Antarctic and subantarctic fur seals at Ile de la Possession, Iles Crozet, Southern Indian Ocean

Luque, Sebastian (2009) Maternal and pup growth strategies of sympatric Antarctic and subantarctic fur seals at Ile de la Possession, Iles Crozet, Southern Indian Ocean. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Otariid pinnipeds exhibit large variation in lactation duration, and pups wean at different times of cycles in marine productivity. Interspecific comparisons to understand the mechanisms driving variation in maternal care strategies and pup development are difficult due to inability to control for confounding effects of differences in environment. Therefore, I investigated interspecific differences in foraging ecology, allocation of maternal resources into pups, and use of maternal resources by pups as they approach weaning, between sympatric Antarctic (AFS) and subantarctic (SFS) fur seals at He de la Possession, lies Crozet, Southern Indian Ocean. Females of both fur seal species fed on the same myctophid fish prey over largely overlapping areas, with minor but important differences in the proportion of prey species consumed. SFS females showed less diel variation in diving behaviour, suggesting that they followed the nycthymeral migrations of their prey to a smaller extent than AFS. Diving occurred exclusively at night in both species, but SFS females dove deeper and for longer periods. AFS females had smaller aerobic dive limit (ADL), but had higher propensity to dive anaerobically. AFS females exploited more patches per unit time, and remained in them for briefer periods of time. AFS females foraged in patches of better quality, at the cost of greater foraging effort. Body shape differed significantly between species from birth, and growth involved the acquisition of a longer, more slender body with larger foreflippers in AFS. Allometric analysis showed that body shape differences present at birth were exacerbated during growth, so AFS were physically more mature at 100 d of age. Milk composition did not differ between species, and total energy intake was significantly higher in AFS at any given age. SFS pups had proportionally larger total body lipid reserves, and had lower resting and daily metabolic rates than AFS pups. Results suggest that, under comparable foraging conditions, maternal expenditure is larger in AFS, in response to a relatively briefer and more inflexible duration of lactation.

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