At-sea behaviour of central-place foraging fur seals and penguins in the Southern Ocean is understudied during the latter stages of parental care and the subsequent pre-moulting period. This biologically important period is costly to investigate due to the risk (or certainty) of losing tracking instruments when the animals moult. Early in this period, parents must meet the increasing demands of larger, more mobile offspring that are still nutritionally dependent and then the parents must recover lost body condition prior to the onset of their annual moult. This study reports late-season, at-sea movement patterns of macaroni penguins, chinstrap penguins and adult female Antarctic fur seals from the subantarctic island Bouvetøya, in relation to remotely-sensed oceanographic features. Foraging trips differing significantly in direction and distance travelled compared to those performed earlier in the breeding season, coincide with the time when offspring would be expected to become independent. On these trips, macaroni penguins moved towards the Polar Front while chinstrap penguins and Antarctic fur seals moved southward. Individuals from all three species appeared to target submesoscale ocean features once they were presumed to have been released from the constraints of feeding their young and were able to travel greater distances from the colony.

The female attendance behaviour of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (A.tropicalis), which breed sympatrically on subantarctic Marion Island, was investigated. Over the same period after the breeding season, the mean duration of feeding trips to sea, and percentage of time spent at sea, did not differ significantly between lactating females of the two species. The difference in mean duration of shore visits was significant and the longer onshore attendance of A. tropicalis probably related to the lower demand by their pups which grow at a slower rate. The subpolar maternal adaptations of A. gazella were unchanged under the more temperate environment at Marion Island, and it remains to be established unequivocally whether conditions there are limiting to the species.

The diet of mainly adult and sub-adult male Antarctic fur seals (Arctocephalus gazella) was investigated during the austral winters of 1992 and 1993 using faecal (scat) analysis. Of samples containing identifiable prey remains (n = 376), c. 28% contained krill alone, c. 37% contained fish alone and c. 35% contained both krill and fish. The mean size of krill taken was smaller than in summer due to the absence of large adult krill of 55–60 mm total length. Of the 25 fish taxa taken, krill-feeding species predominated, especially in scats that also contained krill. Non-krill feeding species were more abundant in scats containing fish alone. The mackerel icefish (Champsocephalus gunnari Lönnberg 1905), which feeds mainly on krill, was the most important fish species in terms of absolute frequency (53%), frequency of occurrence (69%) and estimated biomass (47%); fur seals may have a significant impact on local stocks of this species. Cephalopods and pelagic fish (myctophids) were of minor importance in the diet (<2%). The importance of krill and krill-feeding fish species suggests that the male fur seals, which are present around South Georgia in winter, are targeting their foraging on a krill and fish community, probably associated with krill aggregations.

Southern fur seals Arctocephalus australis in Peru have declined gradually over the past decade, and declined dramatically (72%) as a result of low food availability during the severe El Niño in 1997–98. In 1999, seals abandoned some historically important breeding sites. This is particularly alarming because new sites were not colonized. Our objective was to examine how habitat features and human disturbance influenced whether sites were currently used, abandoned or apparently not used in the past by fur seals for breeding. Data were collected on 14 variables at 70 potential breeding sites at three guano reserves in Peru. Discriminant analysis revealed significant multivariate differences among sites currently used for breeding, abandoned sites and unused sites (F=5.97, P<0.00001), and the model classified 74% of sites correctly. Currently used sites were less likely to have human disturbance and more likely to have offshore islands, stacked rocks, tide pools and abundant shade. Separate discriminant analyses for each reserve produced similar results. Habitat associated with thermoregulation (e.g. shade or pools) may be more important to fur seals in Peru, which breed at lower latitudes and are at greater risk of overheating on land than other populations. Habitat with minimized human access may be especially important to seals in small populations in which individuals may perceive themselves as more vulnerable because of decreased vigilance and dilution effects. Seals in our study selected breeding habitat with stacked rocks, which create shade and tide pools for thermoregulation and make human access difficult; but pups might suffer higher mortality in this habitat. We hypothesize that fur seals in Peru may exhibit an Allee effect, whereby suitability of habitat varies with population abundance.

The analysis of life-history traits suggests that the age and size of female mammals at parturition will affect the birth size and survival of their offspring. We collected data from 252 mother–pup pairs of northern fur seals on Bering Island, Russia, during the 1994 and 1996 breeding seasons to determine the interrelationships among the mothers' age and mass, the sex of the pup, the parturition date, and the length and mass of the pup at birth. Among reproductive females of 19 years, mass increased with age. The mean mass of the oldest class of females (20–23 years) was lighter than the 16–19 year age group but not different from the mean mass of the 7- to 15-year-old females; a quadratic model of mass on age gave similar results, and indicated a maximum mass at age 19 years. We suggest that this may be an effect of a higher rate of survival among leaner animals. Female pups were lighter than males at birth. There was no evidence that the sex ratio of pups differed from 1:1 over the range of observed mothers' mass and age or parturition dates. Older mothers tended to give birth earlier than younger mothers, and heavier mothers earlier than lighter mothers. The relationship of the size of pups at birth and their mothers' age was adequately described with a quadratic model, which predicted a maximum size for mothers at age 12–13 years. The size of pups at birth and the size of their mothers was described with a logistic model which predicted that the size of pups increased for mothers up to 41 kg, with no further increase for heavier mothers. The total amount of variability in birth size explained by the combined models is < one-third of the total, which implies that other influences, such as the contribution of the fathers and individual variation, are also important. The relative maternal investment, measured as the ratio of pup mass to mothers' mass, ranged from 20% for younger and smaller females to 10% for older and heavier females. In addition, relative maternal investment was found to be higher than for other pinnipeds.