Conservation

As a group reptiles have faced a significant loss of habitat; as early as the 1980's the number of threatened or endangered species of reptiles numbered nearly 100, with turtles comprising more than half of those species (Janzen and Paukstis, 1991). In the twenty years since then, the number has undoubtedly grown.

Turtles worldwide are increasingly threatened as human settlements encroach into natural habitats. Perhaps no group of turtles is as threatened as sea turtles, where a combination of fishing, habitat loss, and poaching has pushed these animals close to extinction in some cases. Conservation efforts over the last several decades commonly involved removal of eggs from nests followed by incubation in captivity and subsequent release into the wild. Unfortunately, prior to the discovery of TSD in sea turtles, countless hatchlings were released with no regard to the sex of the offspring (Janzen and Paukstis 1991). Among sea turtles, TSD has been documented in green turtles (Chelonia mydas), loggerhead turtles (Caretta caretta), olive ridley turtles (Lepidochelys olivacea), and leatherback turtles (Standora and Spotila 1985). All of these species have been the subjects of extensive conservation efforts. Under most incubation situations, the sex ratios were male oriented (Girondot et al 1998).

Caretta caretta, the loggerhead turtle. Photo by J.D. Wilson, used with permission by Micheal Dorcas.

Feminization of sea turtle embryos by either temperature or hormonal control has been proposed as a means of increasing population sizes of sea turtles. Since females produce large numbers of offspring and relatively few males are needed to fertilize a number of females, this may seem to be a sound strategy. However, the evolution of a balanced sex ratio (1:1) characterizes most TSD systems, leading researchers to believe that artificial feminization of embryos would likely lead to selection of masculinizing alleles in the long run. Therefore, the best method for the protection and conservation of these animals is the protection of their habitat and nesting sites, accompanied by measures to protect adult animals as well (Girondot et al 1998).

 

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