Feeding ecology of the East Pacific green sea turtleChelonia mydas agassiziiat Gorgona National Park, Colombia

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 ) 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.

INTRASPECIFIC VARIATION OF THE GREEN TURTLE, Chelonia mydas (CHELONIIDAE), IN THE FORAGING AREA OF GORGONA NATURAL NATIONAL PARK (COLOMBIAN PACIFIC)

“…It has a dark grey to black heart-shaped carapace, sometimes with lighter dots ( Fig. 1A; Pritchard, 1998;Amorocho and Reina, 2007). The yellow morphotype, which can be found over the remaining distribution of C. mydas, has a distinctive yellow to light brown coloration with black streaks ( Fig.…”

“…This indicates that the resources available for turtles at the GNP foraging area are equivalent to those of turtles further north (Baja California), since their CI is similar, and that resources at GNP are sufficient to maintain a healthy CI for C. mydas juveniles in the area. The lower availability and abundance of algae in GNP compared to Baja California might be compensated by the availability of other resources, such as tunicates that provide a high-protein food source (Amorocho and Reina, 2007;Fernández-García et al, 2011;Sampson and Giraldo, 2014). Condition indices have been proposed as indicators of individual health; these indices can be used to compare the well-being of individuals from different populations and can be indicators of changes in the food supply (Bolger et al, 1989).…”

Assortative epibiosis of leatherback, olive ridley and green sea turtles in the Eastern Tropical Pacific

“…Consequently, olive ridley turtles have been recorded inhabiting both oceanic and coastal waters depending on inter-annual patterns in food availability (Plotkin, 2010). Lastly, East Pacific green turtles (referred to subsequently only as green turtles), which are primarily herbivorous (Seminoff et al, 2002;Amorocho & Reina, 2007), forage in shallow coastal habitats, such as gulfs or estuary mouths (Blanco et al, 2012;Hart et al, 2015;P. Santidrián Tomillo & N.J. Robinson, unpublished data).…”

Evidence of migratory movements of olive ridley turtles (Lepidochelys olivacea) along the Brazilian coast

“…These facts, together with the present report, have lead us to believe that L. olivacea could be regularly migrating to the northeastern coast of Rio de Janeiro state, probably using this area as a feeding ground since the northeasterly winds prevailing during the spring-summer generate coastal upwelling (COSTA;FERNANDES, 1993;VALENTIN, 2001). Upwelling areas are often important as sea turtle feeding grounds (POLOVINA et al, 2004;JAMES et al, 2005;AMOROCHO;REINA, 2007). Also, the input of organic matter from the Paraíba do Sul River (21 o 36'57''S -41 o 00'50''W) could contribute to make the north-eastern coast of Rio de Janeiro state an important foraging ground for sea turtles.…”