A review of migratory behaviour of sea turtles off southeastern Africa

The survival of sea turtles is threatened by modern fishing methods, exploitation of eggs and habitat destruction. Forming keystone species in the ocean, their extinction would disrupt the marine food chain in ways as yet unknown. The Indian Ocean has many breeding areas for sea turtles, the southernmost ones being on the Maputaland coast of KwaZulu-Natal, where loggerhead and leatherback turtles nest in large numbers thanks to long-lasting protection programmes. For the leatherback this is the only known nesting site in the entire western Indian Ocean. At the end of the reproductive season, both loggerheads and leatherbacks under- take migrations towards disparate feeding areas. To contribute to their conservation, the migratory behaviour of these animals needs to be understood. Here we review 10 years studying this behaviour using transmitters that telemeter data via satellite. It emerges that these species frequent widely dispersed areas ranging from the Atlantic Ocean to the Mozambique Channel. The migratory behaviour of leatherback and loggerhead turtles is, however, very different, probably due to their differing food requirements. While loggerhead postnesting movements have a truly migratory nature, the large-scale wanderings of leatherbacks are better described as prolonged sojourns in extended feeding areas.