Methodology:

Platform transmitter terminals (PTTs) were deployed on lactating female Antarctic fur seals at Bird Island, South Georgia. PTTs were attached with epoxy glue to the hair along the dorsal midline between the scapulae. The PTTs had a minimum transmission interval of 45 s, and they only operated when the saltwater switch, located close to the base of the antenna, showed that the antenna was out of the water. There was no duty cycling of the PTTs, but they were programmed to switch off after the animals had spent 1 h out of the water. PTTs were deployed annually between 1995 and 2010. In 1995 and 1996 the PTTs were deployed on individuals for two foraging trips. For most other years PTTs were deployed for one foraging trip per individual.

Fieldwork was approved by the British Antarctic Survey Animal Ethics Committee.

All data were collected under permit from the Government of South Georgia and the South Sandwich Islands.

Data collection:

Platform transmitter terminals (PTTs) (1995, 1996:Wildlife Computers, 1 W, 250 to 500 g, up to 15 x9 x3cm; 1997, 1998: Telonics ST-10, 0.5 W, 200 g, 10 x4 x2.5 cm).

Data quality:

The PTT data files include quality information, under the fields loc_class and loc_ind. The loc_class field indicates an error value for the location which is determined by the number of satellites the tag connected with. Codes are detailed in readme.txt file. The loc_ind field indicates the IQ (Quality indicator). This indicator gives information on the transmitter in terms of X and Y. X (the first digit in the loc_ind field) indicates residual error on the frequency calculation. Y (the second digit in the loc_ind field) indicates transmitter oscillator frequency drift between two satellite passes. Meanings of the values of X and Y are detailed in the readme.txt file.