Dispersal of male and female Antarctic fur seals (Arctocephalus gazella)

Abstract

This study examined the foraging locations of adult male and female Antarctic fur seals (Arctocephalus gazella) in the Scotia Sea during the postbreeding period. Satellite transmitters were used to track adult males and females and to obtain information about dive depths. Male fur seals migrated away from the breeding area during the postbreeding period whereas females remained close to the breeding grounds and foraged in the same area during two consecutive years. The most intensive foraging by females was associated with the edge of the continental shelf of South Georgia. Males dived deeper than females. Counts of males at South Georgia and at the South Orkney Islands support the result from satellite tracking data showing that males move from South Georgia to the South Orkney Islands at the end of the breeding season. Unlike males, females were limited in their foraging range by the necessity to return to feed dependent young, so breeding sites are likely to be located close to foraging areas that are optimal for females. Locations used for feeding by females were avoided by males, either because they were suboptimal for males or because foraging by females at South Georgia causes local depletion of food, and males, which have the option to forage further afield, can forage more successfully in regions where there are no females. Comparison with fisheries data also suggests that these fur seals are targeting the most abundant exploitable prey.

Satellite Tracker Deployments On Adult, Male Australian Fur Seals (Arctophalus Pusillus Doriferus): Methods And Preliminary Results

“…Errors in location predictions in our study were greater than those predicted by Argos and greater than those recorded in other studies of marine pinnipeds (e.g., Boyd et al 1998;Bonadonna et al 2000;Vincent et al 2002). Variations in location errors could relate to the quality of transmitters, the behaviour of the seals (such as some seals lying on their sides more frequently than others), or external factors (such as atmospheric conditions at different latitudes, or geological features).…”

“…This behaviour contrasts with other fur seal species (e.g., A. forsteri; Antarctic fur seal, A. gazella; subantarctic fur seal, A. tropicalis), which often forage over oceanic waters (Harcourt and Davis 1997;Boyd et al 1998;Bonadonna et al 2000), and is suggested to reflect either a high availability of prey in Bass Strait, and/ or a reliance on benthic foraging by A. p. doriferus (Arnould and Hindell 2001).…”

Seasonal and interannual variation in foraging range and habitat of macaroni penguins Eudyptes chrysolophus at South Georgia

“…Locations of penguins carrying devices were provided by the ARGOS system and assigned to one of 6 classes (3, 2,1, 0, A, B) depending on their accuracy. Classes 1 to 3 gave positions accurate to within 1 to 2 km, and Class 0 gave positions accurate to 3.8 km on average; only these 4 classes were used in analysis (as in Boyd et al 1998). To verify the location data, the speed (km h -1 ) travelled between adjacent locations within each foraging trip was calculated.…”

Foraging ecology of subantarctic fur seals Arctocephalus tropicalis breeding on Amsterdam Island: seasonal changes in relation to maternal characteristics and pup growth

“…Several recent studies of female fur seals have documented at-sea diving activity in relation to oceanographic features (Boyd et al 1998. During years of normal food availability, females exhibiting shorter trips were shown to maximise the proportion of time spent diving while minimising the time spent travelling and recovering between dives (Boyd et al 1994, Arnould et al 1996, Boyd 1996.…”