Wyneken, Jeanette

Information is lacking regarding the foraging ecology of many sea turtle species. This represents the first long-term study to partition gut content samples to look for differences in diets among seasons, across size classes, or between health or sex categories. In this study complete gut contents from loggerhead sea turtles (Caretta caretta) that stranded on Cumberland Island, Georgia USA from 1979--99 are analyzed (n = 369). The long-term nature of this study and large sample size allows for comparisons of diets across years as well as the categories mentioned above. Diets were shown to shift significantly over the years of the study as well as among seasons. Ontogenetic shifts in diets were also observed, while diets did not seem to differ with sex and apparent health of the turtles. The findings from this study point to potential biases from shorter-term studies that lack a robust distribution of turtle size.

It has been recognized that mortality is high for juvenile stages of long-lived vertebrates such as sea turtles, however few studies have quantified mortality rates. The objective of this study was to assess the relative risk that hatchlings face in their first few minutes in the water, at the commencement of their offshore migration from a natural high-density nesting beach (Juno/Jupiter, FL). I followed 217 hatchlings at night by kayak, as they left the beach and documented the proportion surviving the initial 15 minutes in the water. Of these, 206 survived for an empirical survival rate of 95%. Tarpon were the most common predator observed. This survival rate is much higher than that previously observed at a hatchery (72%); this may be due to temporal and spatial variation in nest location at the natural beach. Juno and Jupiter beaches are therefore highly productive sea turtle rookeries.

The calcium requirement in captive-raised hatchling loggerhead sea turtles (Caretta caretta) was investigated. Comparisons were made among turtles on 6 experimental diets and between captive and wild turtles. Diets consisted of trout chow diets containing 1%, 2%, 3%, or 4% calcium and 1.65% phosphorous, AquaMax 500RTM (2% Ca), and shrimp. Feeding trials lasted 28 days and changes in body size and bone density were measured. The calcium and phosphorous content of foods eaten by post-hatchlings in the sargassum were compared with captive diets. Results showed that shrimp was high in protein and low in calcium, with nearly twice as much P as Ca. The growth trials showed that turtles fed shrimp versus all other diets grew larger. There was no difference in total bone density of any treatment over the study. No signs of hypocalcemia were present, therefore, no lower limit for calcium requirement was determined in this study.