The distribution of foraging activity for female Antarctic fur seals was investigated at Cap Noir (49°07' S, 70°45' E), Kerguelen Island in February 1998. Eleven females were fitted with a satellite transmitter and time-depth recorder. The 2 data sets were combined in order to locate diving activity of the seals. The occurrence of fish in the diet of the seals was investigated by the identification of otoliths in 55 scats collected at the breeding colony during the study period. Oceanographic variables were measured simultaneously by direct sampling and satellite remote sensing. The mesopelagic fish community was sampled at 20 stations along 4 transects, where epipelagic trawls were conducted at night at 50 m depth. We then investigated, using geographic information systems, the relationship between the spatial distribution of diving activity of the seals and oceanographic variables (sea surface temperature, surface chlorophyll concentration, prey distribution and bathymetry) at the same spatio-temporal scale. An inverse relationship was found between the main fish species preyed on by the fur seals and those sampled in trawl nets. However, diving activity of the seals was significantly related to oceanographic conditions, forage fish distribution and distance from the colony, although these relationships changed with the spatial scale investigated. A probabilistic model was developed for the distribution of diving activity, which predicted where females should concentrate their foraging activity according to the oceanographic conditions of the year, and where breeding colonies should be located.

This study examins the intra-and inter-individual changes in the foraging route-choice behaviour of 45 female Antarctic fur seals Arctocephalus gazella breeding at the Cap Noir colony in the Kerguelen Archipelago, southern Indian Ocean. Satellite transmitters were used to track seals during one or more consecutive foraging trips in 3 consecutive austral summers (1998 to 2000). In all years of study the seals showed a 'colony-preferred direction', concentrating their trips at sea in a 140°arc east of Kerguelen, indicating a preferred area for foraging. Within this area, lactating females travelled in 1 of 2 main directions: north east toward the edge of the Kerguelen plateau; and less commonly, east/south east. Each direction led seals to sub-areas characterised by different bathymetric features where animals appeared to use different tactics to search for food patches. Moreover, a fidelity index incorporating the mean direction of successive trips and the colony preferred direction indicated the existence of an individual directional fidelity. The organisation of foraging trips suggests 2 levels of learning by seals: a colony memory of the main foraging zone and an individual memory of profitable patches that are exploited by the same individual during successive trips. KEY WORDS: Antarctic fur seal · Satellite transmitter · Foraging trip · Kerguelen Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 223: [287][288][289][290][291][292][293][294][295][296][297] 2001 mation could improve their efficiency in relocating patches without wasting time searching and sampling other patches. For example, after a profitable trip predators could learn the position of the patch and return to it on the successive trip. The more learnt, the less time spent searching and sampling.Antarctic fur seals Arctocephalus gazella are top marine predators and, as with all otariids, commute between their colonies and feeding areas during the pup-rearing period (Gentry & Kooyman 1986). Consequently, Antarctic fur seals must deal with the problem of finding food. Although diving behaviour and foraging effort of this species at sea have been studied extensively in South Georgia (Costa et al. 1989, Boyd et al. 1991, Boyd & Croxall 1992, Boyd et al. 1994, Arnould et al. 1996, Boyd 1996, little is known about dispersal patterns while seals are foraging at sea (Boyd et al. 1998, Bonadonna et al. 2000. Antarctic fur seals breeding in South Georgia appear to utilise the same area over 2 consecutive years, and in the same breeding season lactating females head in the same direction over 2 consecutive trips (Boyd et al. 1998, Boyd 1999. This tendency can also be seen in the northern fur seal Callorinus ursinus (Loughlin et al. 1987). However, in the case of the South Georgian fur seals, the fidelity to the same direction over consecutive trips could be an artefact of the narrow sector in front of the colony (< 60°) exploited by the population during foraging trips, and individuals could kno...

Maternal allocation to growth of the pup was measured in Antarctic fur seals (Arctocephalus gazella) at the Kerguèlen Islands during the 1997 austral summer. Absolute mass gain of pups following a maternal foraging trip was independent of the sex of the pup but was positively related to foraging-trip duration and maternal length. However, daily mass gain (i.e., absolute mass gain of the pup divided by foraging-trip duration) decreased with increasing foraging-trip duration but increased with maternal length. While the pup were fasting, their daily mass loss was related to their sex and initial body mass: both heavier pups and female pups lost more mass per day than lighter pups and male pups. The mass-specific rate of mass loss was significantly higher in female than in male pups. Over the study period, the mean growth rate was zero, with no difference between female and male pups. The growth rate in mass of the pup was positively related to maternal length but not to maternal condition, and negatively related to the foraging-trip duration of the mother and the initial mass of the pup. This indicates that during the study period, heavier pups grew more slowly because of their higher rate of daily mass loss during periods of fasting. Interestingly, for a given maternal length, the mean mass of the pup during the study period was higher for male than for female pups, even though the rate of daily mass gain was the same. Such differences are likely to result from sex differences in the mass-specific rate of mass loss. As female pups lose a greater proportion of their mass per day, a zero growth rate (i.e., mass gain only compensating for mass loss) is reached at a lower mass in female pups than in male pups. Our results indicate that maternal allocation does not differ according to the sex of the pup, but suggest that the two sexes follow different growth strategies. 483 Résumé : L'allocation des ressources de la mère à son petit a été étudié chez l'Otarie de Kerguelen (Arctocephalus gazella) aux Îles Kerguelen pendant l'été austral 1997. Le gain de masse absolu du petit après une excursion alimentaire de sa mère était indépendant de son sexe, mais était significativement relié à la durée de l'excursion et à la longueur de la mère. Cependant, le gain de masse quotidien (i.e., le gain de masse absolu du petit divisé par la durée en jours de l'excursion alimentaire de la mère) diminuait avec l'augmentation de la durée des séjours en mer mais augmentait en fonction de la longueur de la mère. Pendant les périodes de jeûne, la perte de masse quotidienne du petit dépendait de son sexe et de sa masse initiale, les taux de perte de masse étant plus élevés chez les femelles et les petits les plus lourds. La perte de masse spécifique était également significativement plus élevée chez les petites femelles comparée aux petits mâles. Pendant la période d'étude, le taux de croissance pondérale moyen était nul, et aucune différence n'a été observée entre les petit mâles et les petites femelles. Le taux de croissance pondérale étai...