Satellite Tracking of Head-Started Juvenile Green Turtles (Chelonia mydas) Reveals Release Effects and an Ontogenetic Shift

Juveniles of marine species, such as sea turtles, are often understudied in movement ecology. To determine dispersal patterns and release effects, we released 40 satellite-tagged juvenile head-started green turtles (Chelonia mydas, 1–4 years) from two separate locations (January and July 2023) off the coast of the Cayman Islands. A statistical model and vector plots were used to determine drivers of turtle directional swimming persistence and the role of ocean current direction. More than half (N = 22) effectively dispersed in 6–22 days from the islands to surrounding areas. The January turtles radiated out (185–1138 km) in distinct directions in contrast to the northward dispersal of the July turtles (27–396 km). Statistical results and vector plots supported that daily swimming persistence increased towards the end of tracks and near coastal regions, with turtles largely swimming in opposition to ocean currents. These results demonstrate that captive-reared juvenile greens have the ability to successfully navigate towards key coastal developmental habitats. Differences in dispersal (January vs. July) further support the importance of release timing and location. Our results inform conservation of the recovering Caymanian green turtles and we advise on how our methods can be improved and modified for future sea turtle and juvenile movement ecology studies.

Lesions Observed Post Mortem in Post-hatchling Loggerhead Sea Turtles (Caretta caretta) from a Head Start Programme

Head start programmes are ex-situ conservation procedures consisting of the captive rearing of sea turtle hatchlings for several months in order to avoid high mortality rates in the first year of life. Studies of the diseases of hatchling and post-hatchling turtles belonging to these programmes are scarce. We describe the gross and histological lesions found in 78 post-hatchling loggerhead sea turtles (Caretta caretta) that died during captive rearing in the conservation programme of the Cape Verde-Canary Islands, initiated with 113 hatchlings. The main organ systems affected were respiratory (57.69%), integumentary (41.02%) and digestive (41.02%), affecting 94.87% of the animals. Other less frequently affected organ systems were cardiovascular (3.85%), excretory (3.85%), muscular (2.56%) and reproductive (1.28%). The most common lesions were different types of dermatitis (41.02%), mainly ulcerative and/or heterophilic ulcerative dermatitis; these lesions were compatible with a traumatic origin caused by biting and subsequent infection with gram-positive cocci. Purulent and/or fibrinonecrotizing rhinitis associated with mixed populations of bacteria were commonly detected respiratory lesions (21.79%). Acute interstitial pneumonia was the most common form of pneumonia diagnosed (20.51%). Fibrinonecrotizing stomatitis associated with sparse gram-negative rods was the most common digestive tract lesion (29.49%). A possible explanation for the high mortality rate (88.50%) observed in this study could be the occurrence of a decrease in water temperature during the growth phase of the turtles. Despite the limitations caused by an absence of microbiological studies, the survey provides useful information on the lesions found in post-hatchling loggerhead turtles from this head start programme. In addition to maintaining water temperature above 20°C, attention must be paid to lesions that can easily be detected, such as dermatitis, rhinitis and stomatitis.