The effects of extended crawling on the physiology and swim performance of loggerhead and green sea turtle hatchlings

Following emergence from the nest, sea turtle hatchling dispersal can be disrupted by artificial lights or skyglow from urban areas. Misorientation or disorientation may increase exposure to predation, thermal stress and dehydration, and consume valuable energy, thus decreasing the likelihood of survival. In this study hatchlings were run on a treadmill for 200 or 500 m to investigate the physiological impacts of disorientation crawling in loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle hatchlings. Oxygen consumption, lactate production and blood glucose levels were determined, and swim performance was measured over 2 h following crawls. Crawl distances were also determined for hatchlings that disoriented on the Boca Raton beach in Florida, with plasma lactate and blood glucose sampled for both properly oriented and disoriented hatchlings. Green and loggerhead hatchlings rested for 8-12% and 22-25% of crawl time, respectively, both in the laboratory and when disoriented on the beach, which was significantly longer than the time spent resting in non-disoriented turtles. As a result of these rest periods, the extended crawl distances had little effect on oxygen consumption, blood glucose or plasma lactate levels. Swim performance over 2 h following the crawls also changed little compared with controls. Plasma lactate concentrations were significantly higher in hatchlings sampled in the field, but did not correlate with crawl distance. The greatest immediate impact of extended crawling as a result of disorientation events is likely to be the significantly greater period of time spent on the beach and thus exposure to predation.