Sun exposure, nest temperature and loggerhead turtle hatchlings: Implications for beach shading management strategies at sea turtle rookeries

Sea turtle incubation biology is tightly linked to nest thermal conditions due to the effect temperature has on hatching success, sex determination, morphology and locomotion performance. Because of this relationship between nest temperature and hatchling outcomes, global warming presents an immediate threat to many sea turtle nesting beaches throughout the world. Even small rises in nest temperatures may skew sex ratios and, raise egg mortality and influence hatchling phenotypes adversely, impacting on hatchling recruitment and ultimately species survival at some rookeries. The development of adaptive management practices capable of minimizing the effects of increasing global temperature on nest temperatures is thus a priority for animals exhibiting temperature-dependent sex-determination, such as sea turtles. Here, the relationship between solar radiation exposure and nest temperatures at the Mon Repos turtle rookery, south east Queensland, Australia was explored and the relationship between nest temperature and hatchling attributes examined. Shading decreased nest temperature, and higher nest temperatures were associated with smaller sized hatchlings that had decreased locomotion performance. The use of shading to minimize nest temperature is a management strategy that may be used to mitigate detrimental effects of increased global temperatures at some rookeries. Here, we explored the viability of natural shading options, such as the planting of trees behind nesting beaches, for combating the adverse effect of increased nest temperature caused by increased air temperatures.