Sex Ratios In Sea Turtles

Sea turtles are threatened and endangered throughout their natural range due to various anthropogenic interferences, such as poaching and habitat destruction (World… c2016). Sea turtles provide many ecological benefits, such as acting as distributors of nutrients and sculptors of both terrestrial and marine substrate (Mancini et al. 2011). However, global climate change is threatening sea turtle populations’ ability to continue to provide these benefits (Mancini et al. 2011). Beach habitat loss due to sea level rise is one aspect of global climate change that affects the nesting range of sea turtles (Fish et al. 2008). Another aspect of climate change is the gradual warming of the atmosphere. Since sea turtles are reptiles who bury their eggs,
2010). According to Charnov and Bull (1977), genotypic sex determination (GSD) is less beneficial than environmental sex determination, such as TDS, when environments are not stable and the sexes have a dissimilarity in reproductive fitness. Sex ratios in sea turtles are usually female-biased due to increased incubation periods, which can lead to intensified populations of females while male populations are less supported (Tomillo 2015). The transitional range of temperature (TRT) is where the offspring being produced is a mixture of both sexes, rather than all male or all female (Mrosovsky and Pieau 1991). The TRT of sea turtles is about 1°C. Current global climate change predictions indicate that the air temperature will reach 1° to 4°C warmer than the current climate by the end of the 21st century. Since this rate of temperature increase would surpass the TRT of sea turtles, it is possible that all hatchlings produced will be female by the end of the 21st century (Tomillo 2015). Under climate change scenarios where gas emissions and concentrations increase, TDS has been shown to be ineffective in the sustainability of the population due to disproportional sex ratios (Figure 1, Tomillo 2015). GSD populations were more negatively affected than TSD populations in low gas emission in both current mean temperatures and temperatures lower than the current mean temperatures
2015). Water cool nests to bring the temperature of the nest down far enough to stimulate embryonic development and/or male production (Laloë et al. 2015). However, too much water can cause the gas exchange to be limited causing mortality due to suffocation in the nest (Chen et al. 2010). The concentration of water in nests is directly affected by variations in rainfall and temperature (Tomillo et al. 2012). For example, the El Niño Southern Oscillation causes higher hatchling mortality due to drier and warmer conditions in Costa Rica (Tomillo et al. 2012). It is predicted that hatchling survival will drop by 50 to 60% within the next 100 years in that region (Tomillo et al. 2012). However, due to global climate change, regions also facing drier and warmer conditions may face similar declines in hatchling survival