Feeding ecology of juvenile green turtles in food-poor habitats of the Persian Gulf

Abstract

The Persian Gulf hosts marine mega-herbivores that forage in its coastal habitats. Some areas, mainly along its southern coast, contain abundant benthic plants; however, marine plant resources are limited throughout most of this warm sea, which presents nutritional challenges for large herbivores. We measured curved carapace length (CCL) for 102 green turtles (Chelonia mydas) from foraging grounds with relatively limited plant resources surrounding Qeshm Island at the eastern Persian Gulf. The mean CCL was 41.8 cm (SE = ± 1.3 cm; range = 18.5–99), and 93 turtles (91%) had CCL < 65 cm, indicating the area is primarily a juvenile developmental habitat. To study feeding ecology of green turtles in the area, we analyzed esophageal lavage samples from 36 individuals captured in muddy-bottom (n = 23) and sandy/rocky-bottom (n = 13) habitats. Diet data showed a generalist foraging population with dietary niche variation among individuals that targeted mixtures of macroalgae, seagrasses and mangrove. Green turtles showed a slight preference for green algae (Ulva sp.) at both sites. The mean Fulton’s body condition index for juvenile turtles was 1.14 (SE = ± 0.03; n = 72), which is comparable to values reported elsewhere, and indicates that these turtles were not under-nourished. This is intriguing in light of the paucity of local food resources, and perhaps due to the absence of large sub-adults and adults with higher food demand, and/or individual dietary niche variation among resident turtles, both of which reduce competition among local green turtles for the region’s available resources.