Water temperature data from southern elephant seal from Marion Island with links to datasets

As the Antarctic Circumpolar Current crosses the South-West Indian Ocean Ridge, it creates an extensive eddy field characterised by high sea level anomaly variability. We investigated the diving behaviour of female southern elephant seals from Marion Island during their post-moult migrations in relation to this eddy field in order to determine its role in the animals' at-sea dispersal. Most seals dived within the region significantly more often than predicted by chance, and these dives were generally shallower and shorter than dives outside the eddy field. Mixed effects models estimated reductions of 44.33 ± 3.00 m (maximum depth) and 6.37 ± 0.10 min (dive duration) as a result of diving within the region, along with low between-seal variability (maximum depth: 5.5 % and dive duration: 8.4 %). U-shaped dives increased in frequency inside the eddy field, whereas W-shaped dives with multiple vertical movements decreased. Results suggest that Marion Island's adult female elephant seals' dives are characterised by lowered cost-of-transport when they encounter the eddy field during the start and end of their post-moult migrations. This might result from changes in buoyancy associated with varying body condition upon leaving and returning to the island. Our results do not suggest that the eddy field is a vital foraging ground for Marion Island's southern elephant seals. However, because seals preferentially travel through this area and likely forage opportunistically while minimising transport costs, we hypothesise that climate-mediated changes in the nature or position of this region may alter the seals' at-sea dispersal patterns.

Dive depth profile and immobilisation data of adult male and female Weddell seals at Drescher Inlet from expedition DRE1998

Adult male and female Weddell seals (Leptonychotes weddellii) were fitted with Time-depth recorders (TDR) at Drescher Inlet (Riiser Larsen Ice Shelf), eastern Weddell Sea coast, in February 1998. Eight of 15 data sets were selected for analyses to investigate the seals' foraging behaviour (doi:10.1594/PANGAEA.511465, doi:10.1594/PANGAEA.511454, doi:10.1594/PANGAEA.511456, doi:10.1594/PANGAEA.511457, doi:10.1594/PANGAEA.511459, doi:10.1594/PANGAEA.511462, doi:10.1594/PANGAEA.511466, doi:10.1594/PANGAEA.511467). These data sets provided simultaneous dive records of eight seals over eight days. The seals primarily foraged within two depth layers, these being from the sea surface to 160 m where temperature and salinity varied considerably, and from 340 to 450 m near the bottom where temperature was lowest and salinity highest, with little variation. While pelagic and benthic diving occurred during daylight, the seals foraged almost exclusively in the upper water column at night. Trawling during daytime confirmed that Pleuragramma antarcticum were by far the most abundant fish both in the pelagial and close to the bottom. Pelagic night-hauls at 110-170 m depth showed highly variable biomass of P. antarcticum with a peak at around midnight. The temporal changes in the local abundance of P. antarcticum, particularly in the pelagial, may explain the trends in the seals' pelagic and benthic foraging activities. This is the first study which describes the jaw movements of a hunting seal which are presumably indicative of feeding events. Trophic links from the Weddell seal to fish, zooplankton and krill, Euphausia superba, are discussed. Another seven data sets did not overlap substantially with the selected time frame (doi:10.1594/PANGAEA.511458, doi:10.1594/PANGAEA.511460, doi:10.1594/PANGAEA.511464, doi:10.1594/PANGAEA.511468, doi:10.1594/PANGAEA.511469, doi:10.1594/PANGAEA.511453, doi:10.1594/PANGAEA.511463). A total of 25 Weddell seals were immobilised during the study period using a combination of ketamine, xylazine, and diazepam. Seven seals were drugged once, 15 seals two times, and three were drugged three times, coming to a total of 46 immobilisation procedures. Narcoses were terminated with yohimbine (doi:10.1594/PANGAEA.438933).

At surface behaviour at location on spot of southern elephant seals from Marion Island in 2004 with links to datasets

A novel classification system was applied to the sea level anomaly (SLA) environment around Marion Island. We classified the SLA seascape into habitat types and calculated percentage of habitat use of ten juvenile southern elephant seals (SES). Movements were compared to SLA and SLA slope values indicative of ocean eddy features. This classification provides a measure of habitat change due to seasonal fluctuations in SLA. Some of the seals made two migrations in different seasons, each of similar duration and proportions of potential foraging behaviour. The seals in this study did not use any intense eddy features, but their behaviours varied with SLA class. Potential foraging behaviour was positively influenced by negative SLA values (i.e. areas of below average sea surface height). Searching behaviour during the winter was more likely at eddy edges where high SLA slope values correlated with low SLA values. Though the seals did not forage within newly spawned eddies, they did forage near the sub-Antarctic front. Plankton and other biological resources transported by eddies formed at the subtropical convergence zone are evidently concentrated in this region and enhance the food chain there, forming a foraging ground for juvenile SES from Marion Island.