A Tri-National Aerial Survey of Leatherback Nesting Acivity in New Guinea and The Solomon Islands

Abstract

Endangered Western Pacific leatherback sea turtles, Dermochelys coriacea, form an ecologically diverse metapopulation, which forages in several tropical and temperate regions of the Pacific and Indo-Pacific region. Multiyear satellite telemetry studies at Bird’s Head Peninsula, Papua Barat, Indonesia; Huon Gulf, Papua New Guinea; and Santa Isabel Island, Solomon Islands have revealed variations in migratory routes and foraging destinations, and links to oceanographic processes. The most apparent pattern in this dataset (n=91) is a clear separation of migratory destinations for boreal summer (July) vs. boreal winter (December-February) nesters. Individuals nesting in Papua Barat, Indonesia during July (2003, 2005, 2006, 2007) migrated to foraging areas within multiple temperate regions of the North Pacific Ocean and tropical waters of the South China Sea, remaining north of the equator at all times. In contrast, individuals tagged at the same Papua Barat beaches during January-February (2005, 2007) moved southward, similar to nesting leatherbacks tagged during these months in Papua New Guinea and the Solomon Islands (2001, 2003, 2006). Destinations for these boreal winter nesters included the temperate South Pacific between southeastern Australia and New Zealand’s North Island, and tropical regions south of the equator, particularly the Banda Sea. The arrival of leatherbacks at northern temperate destinations coincided with periods of peak marine productivity. Off the U.S. West Coast, leatherbacks arrived during July-August to exploit the seasonal dense aggregations of sea nettles, Chrysaora fuscescens, an important prey species. We hypothesize that the timing of arrival at southern temperate destinations also coincides with peak prey availability in these locations