Patterns and impacts of oiling of African penguins Spheniscus demersus: 1981–1991

Abstract

A total of 4 215 oiled African penguins Spheniscus demersus recovered from beaches and at breeding localities around the southern African coast were admitted to the SANCCOB rescue station over the period 1981–1991. This is 24% less than recorded during the previous 11 years. The admission rate of 2.47 individuals per 1000 in the 1970s is similar to the 2.35 individuals per 1000 recorded in the 1980s in spite of a substantial decrease in the volume of oil transported around the South African coast over the last decade. This may be explained by a regional shift in the distribution of the penguin population. Seventy-seven percent of the total population now breeds along the south coast of the subcontinent in an area where the risk of encountering oil is highest. The increased risk is a consequence of important shipping lanes passing close to the major concentrations of penguins at Dyer and St Croix Islands and probably the system of currents which moves oil onshore, at least east of Cape Agulhas. A winter peak in the incidence of oiling of penguins is probably related to breeding and associated commuting to and from feeding areas at sea. This increases the likelihood of penguins encountering oil in the vicinity of nesting sites. Impacts of oiling at the population level apparently remain similar to that noted in the previous decade, with a minimum annual admission rate of oiled penguins to the rescue station of 0.24% of the total population. However, the risk of a single incident affecting a substantial part of the population has increased markedly.