This dataset contains stable isotope and tracking data from adult female Antarctic fur seal collected at three breeding colonies across the Southern Ocean: • Marion Island (2008–2018) • Bird Island, South Georgia (2008–2012) • Cape Shirreff, South Shetland Islands (2008–2012) The dataset includes: • Stable isotope data from whole blood and whiskers • Compound-specific amino acid isotope data (δ¹⁵NAA) from whole blood • GLS-derived tracking and environmental data Samples were collected from adult female seals captured between February and April prior to winter migration. Whole blood samples provide dietary information integrated over approximately 2–3 months, while sequential whisker sections provide longer-term isotopic records spanning multiple years. Bulk stable isotope values (δ¹³C and δ¹⁵N) and compound-specific isotope analysis of amino acids (CSIA-AA) provide information on trophic ecology and foraging habitat across multiple temporal scales, from recent feeding behaviour to multi-year dietary histories recorded in whiskers. The dataset also includes light-based geolocation (GLS) tracking data from adult females equipped with geolocator loggers during the inter-breeding migration period. Tracking variables include timestamps (GMT), estimated geographic positions (latitude and longitude), uncertainty metrics, and associated environmental variables such as sea surface temperature (SST) and absolute dynamic topography (ADT), where available.

Raw time series of depth, water temperature, light and swim speed. Stomach temperature and heart rate are available in some instances, but the data is sparse. Data was collected using time/depth recorders and satellite telemetry. Ancillary location was recorded from a separate logger.