A Literature Review of the Effect of Temperature on Sex Ratios of Sea Turtle Hatchlings

All species of sea turtles depend upon available beach to reproduce. Sea turtle rookeries are threatened by factors like erosion, predation, and increasing global temperatures. Unlike most dioecious species in which males and females are produced in somewhat equal numbers, sea turtle sex ratios vary widely from one geographic area to another. This is due to the fact that the sex of sea turtles is dependent upon the incubation temperature of the nest, specifically at the middle third trimester of embryonic development. The purpose of this literature review is to examine current research on the methods used to estimate sea turtle hatchling sex ratios and to list the estimated sex ratios known for the loggerhead, green, leatherback and Kemp’s ridley species known at this time. Although various methods are employed, using sand temperatures coupled with published pivotal temperature and constant temperature equivalents (CTE’s) seems to be the most convenient and reliable. Other factors that affect nest temperature such as nest location, sand characteristics, shading, weather and metabolic heating can also have a significant impact on sex ratios. Overall, sex ratio studies have shown that beaches closer to the equator tend to be female biased, where sub-polar beaches produce more males. Sex ratios of hatchlings across the globe tend to be female biased. However, sex ratio studies on juvenile and adult studies show sex ratios closer to the expected 1:1. Future interpretation and application of sex ratio studies for the purposes of conservation will require a better understanding of sea turtle mating systems