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Leopard seal studies on Bird Island

Leopard seals have been monitored at Bird Island since the early 1980s and in 1993 the first individuals were given identification tags to initiate a long-term study. In 2005 the tagging programme was augmented with photo-identification, to improve individual recognition rates. Modelling the prey choice, based on opportunistic diet data collection, together with the arrival, residence and departure times of monitored individuals we obtain estimates of seasonal abundance of leopard seals and prey consumption. Three main sources of data are produced as part of this programme.

Leopard Seal (Hydrurga leptonyx) on the concrete slipway at Signy Island.
Leopard Seal (Hydrurga leptonyx) on the concrete slipway at Signy Island.

Total seasonal counts

All observations of leopard seal individuals (identified or unidentified) are recorded on a daily basis during the austral winter and early spring, when the seals disperse from the pack ice and temporarily use Bird Island to find prey and rest ashore.

Seasonal number of individuals

Using the individually unique fur patterns of leopard seals through photo-identification, and reading the plastic tags given to a number of individuals every year, we produce the minimum observed number of individuals.

Counts of leopard seals at Bird Island

Opportunistic diet data collection

Using observations on feeding behaviour and scats we study the seals’ diet throughout the winter. The diet data are used in studies of prey-preference variability (between individuals and over time), and to assess predation impacts on the main prey populations (gentoo penguins and fur seals).