Sea turtle hatchlings do not have external characteristics for sex identification. This can only be determined through the analysis of a small sample of tissue or blood, but most ecologists prefer to avoid these invasive methods and rely on other measurements to estimate the sex ratio.
It is generally known that sea turtle sex determination is temperature-dependent. If the sand temperature is below 29ºC (82 °F), the hatchling is more likely to be male. Above this pivotal temperature, it is more likely to be a female. Throw in a few environmental factors from the area and a handful of statistics and probability equations, and you may get a good estimation of the sex ratio. Some scientists go even further and only use the external factors, such as local weather data and sea surface temperature, without bothering to go to the beach and measure the actual sand temperature. How useful can these models really be?
While this may seem like a numbers game of only academic interest, the outcome can really help us answer a critical question faster than we would need if we gathered all the evidence needed: will climate change drive sea turtles to extinction? All their species are already endangered, and an unbalanced sex ratio could be a threat more important than other human-made threats.
And even more importantly, if climate change is a threat to sea turtles, what can we do about it? In addition to trying to avert climate change, this question has increased the significance of areas where there are only a few nests every year, but are more likely to produce equal numbers of male and female hatchlings as global temperatures increase. These are the areas at the northern margins of sea turtle nesting regions.