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Brown rats were introduced to the sub-antarctic island of South Georgia probably around 1800. They are now widespread and abundant, particularly on the north coast. The population is divided into discrete units by the rugged topography of the island, particularly the many glaciers. Rats are found mostly in dense stands of coastal tussock grass which provides both shelter and food. They dig burrows in the tussock stools and make nest chambers in the leaf canopy. Tussock, which is rich in carbohydrate, forms the main part of their diet throughout the year. Perimylopid beetles are regularly eaten, and the rats forage on the sea-shore. Carrion is eaten where available and the rats prey on ground-nesting birds. Breeding is probably seasonal, as litters were found only from December to February. The rats have adapted successfully to the rigorous South Georgia climate, but are dependent on tussock grass for their survival. They have made rather little impact on the vegetation. Dove prions, diving petrels and some large petrels are preyed on but breeding colonies of these birds can coexist with rats. The Antarctic pipit rarely if ever nests in rat-infested areas. No management procedures would be possible.