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The paper describes the occurrence of Killer whales at Marion Island (Prince Edward group) in the south Indian Ocean from August 1973 to November 1976. They occur seasonally, being most numerous from October to December. Their occurrence is synchronized with the seasonal haul out of Southern elephant seals, but the seasonality of King, Rockhopper and Macaroni penguins is also likely to influence their occurrence. The largest herds occur in October, the month during which mean group size is also largest. Sex and age composition are given, adult males being significantly more numerous than adult females, while 36–3 % of the latter had calves. Hunting activity appears to be greatest between 15.00 and 17.00 hrs, and most Killer whales were seen within 100 m of the shore. Aspects of hunting, attacking, feeding and resting behaviour are discussed. The body measurements of a young male found on a beach are given.

With respect to environmental conservation at* the Prince Edward Islands, South Africa has not lagged behind other nations owning sub-Antarctic islands. Indeed, with respect to some aspects, it can claim to be in the forefront. The most serious environmental problems at the Prince Edward Islands have to do with the need for control or eradication of certain established alien species of both plants and animals, the prevention of the introduction of additional aliens, and the carrying out of environmental impact assessments prior to new developments or expansions of existing facilities and programmes. However, where South Africa has lagged behind is in the enunciation of a policy on, and the proclamation of legislation giving, formal status to environmental conservation at, and the implementation of a formal and effective management plan for, the Prince Edward Islands.It is hoped that these shortcomings will be redressed in the near future. But if, for example, an aircraft landing strip were ever to be built on Marion Island, then the need for the proclamation of legislation and the implementation of a management plan would become even greater than at present. Prince Edward Island is so exceptionally special as an undisturbed sub-Antarctic island that it must never be subjected to any such development.

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