ESR 3:43-51 (2007)  -  doi:10.3354/esr003043

ABSTRACT: The diet of 84 East Pacific green turtles Chelonia mydas agassizii, captured in 2003 and 2004 at Gorgona National Park in the Colombian Pacific, was studied through analysis of lavage samples collected from the lower oesophagus. We identified 5 food diet components, with rank in order of percent dry mass being: tunicates (Salpidae and Doliolidae), red mangrove fruits (Rhizophora mangle), algae (Rhodophyta, Chlorophyta, Cyanophyta), small crustaceans (shrimp larvae) and leaves (Ficus spp.). Three non-food diet items included coral fragments, shells, and sand/pebbles that were found in large amounts in most retrieved samples. Nutritional analyses were carried out to determine the contribution of diet components to the foraging turtles. Tunicates had the highest protein value (438 g kg^–1), followed by algae (174 g kg^–1), leaves (170 g kg^–1) and mangrove fruits (65 g kg^–1). The frequency of retrieved components grouped in animal (including coral), vegetal and sand/pebbles categories did not vary between sampling seasons. The immature East Pacific green sea turtle population at Gorgona National Park showed an omnivorous behaviour, feeding on a range of animal and vegetal components with a bias towards tunicates (Salpidae and Doliolidae). In contrast to the generally herbivorous diet of juvenile green turtles (over 40 cm straight carapace length; SCL), Gorgona’s immature population was composed of large juveniles, subadults and a few adults feeding mainly on animal matter. Mean SCL of 86 measured turtles was 58.4 ± 7.8 cm (ranging from 37.0 to 72.9 cm). Mean mass was 28.0 ± 10.7 kg (ranging from 7.5 to 50.5 kg). We speculate that this omnivorous strategy of Gorgona’s immature green turtles might provide energetic benefits for continuing long distance migrations to further developmental or mating grounds in the Pacific basin.

KEY WORDS: Green turtle · Black turtle · Feeding ecology · Omnivory · Nutrition · Migration