The consequences of herbivory for the life history pattern of the Caribbean green turtle, Chelonia mydas

Abstract

The Caribbean green turtle, Chelonia mydas, feeds primarily on the seagrass Thalassia testudinum, which has a high fiber content and thus a low forage quality. The green turtle has two adaptations for its low quality diet: a hindgut fermentation and a selective grazing pattern. Despite these adaptations, the green turtle is nutrient- limited, which results in low growth rares, delayed sexual maturiry, and a low annual reproductive effort. The energy required by a female Tortuguero green turtle is approximately 805,800 kJ per year. The Tortuguero green rurtle, which feeds on T. testudinum, is able to allocate only 10 percent of its annual energy budget for reproduction, while the Surinam green turtle, which feeds on algae, allocates 24 percent of its annual energy budget for reproduction. The carrying capacity of T. testudinum for the green turtle is estimated at 138 adult female green turtles per hectare. The instantaneous death rates for the cohorts of Tortuguero turtles increased from 1959 to 1972,which suggests that the Tortuguero green turtle population has not been maintaining itself. The nutrient limitations imposed on the green turtle by its low-quality diet make it vulnerable to, and slow to recover from, overexploitation of its adult population.