Loggerhead Sea Turtles

between populations with variability of less than a percent between populations (Mrosovsky et al. 2002).

Five years of temperature change could already begin to show some impact on sex ratios of loggerhead sea turtles. The viability of loggerhead sea turtle populations relies on suitable incubation temperatures that produce an adequate proportion of males and females (Ucar et al. 2012). Many species that have temperature-dependent sex determination, already often produce highly skewed offspring sex ratios and loggerhead sea turtles in particular already tend to produce sex ratios skewed toward females. The Earth’s average global surface temperature is currently warming at a rate of more than 0.1 degrees Celsius per decade (Lynch 2011). Five

This is due to what is known as the transitional range of temperatures, which is defined as the range of temperatures at which the sex ratio shifts from 100% male to 100% female (Hanson 1998). The transitional range of temperatures for sea turtles is generally less than 2°C and may be less than 1°C for loggerhead sea turtles. As the mean warming is projected to be over 2°C over the next 100 years, this has serious implications for the sustainability of sea turtle populations (Jribi and Bradai 2014). A rise in 1°C or more in the next fifty years may induce the production of single-sex generations and consequently lead to population extirpation (Hays et al. 2010). If the temperature change is severe enough, the amount of population extirpations may lead to extinction of the entire species. The probability of this is uncertain, as there is a possibility that loggerhead turtles will select different nest sites as warming increases, or rapidly adapt to the changed climate (Deeming and Ferguson 1989). However, a shift in nest site preference is not the most likely option for loggerhead sea turtles, which show strong nest site fidelity. In addition, because nesting females generally return to their natal beaches and there is a low gene flow between nesting assemblages, these populations that are genetically distinct are at risk for extirpation (Ehrhart et al. 2003). Additionally, the potential for loggerheads to choose suitable nest sites is limited by human activity. Sea turtles will be less likely to nest on beaches that have high human recreation or that have been altered by humans. Beaches that are near human development pose a threat to sea turtles, not just by human presence, but because artificial lights prevent hatchlings from being able to orient themselves toward the ocean (Lindsay 2003). Additionally, the possibility of adaptation poses some uncertainties. Loggerhead