Crocodile Sex Is Not Hotter with Global Warming

Crocodiles represent an ancient group of reptiles, closely related to dinosaurs, and appeared in fact at the same time with them, during the Triassic period.

They are the only groups of big sized reptiles that survived dinosaur extinction (other big reptiles that gone extinct at the late Cretaceous, beside dinosaurs, were the marine plesiosaurs and flying pterosaurs). They found a place for themselves even in the "mammal era" after the dinosaurs, but now they face a double threat: human and climate.

With the global warming, crocodiles may find it increasingly difficult to find a partner for a hanky-spanky moment. Cause for crocodiles, as for other reptiles such as turtles, gender does not have a chromosome basis, but rather the incubation temperature activates the gene for maleness or femaleness. And this trait might trick the crocodile populations worldwide. "A difference of 0.5 - 1ºC in incubation temperature results in markedly different sex ratios," said Dr. Alison Leslie, of South Africa's University of Stellenbosch, principal investigator of Earthwatch's Crocodiles of the Okavango Delta project.

Nests at temperatures of about 32-33 degrees Celsius provide males, while temperatures higher and lower provide females. Because usually temperatures within a nest vary from the top to the bottom, the brood use to be of mixed-gender. "More female hatchlings due to the cooler or hotter incubation temperatures could lead to eventual extirpation of the species from an area," says Leslie.

Crocodile populations have dropped dramatically in Botswana, and all around the world, due to overexploitation by hide poaching and conflicts with nearby communities. "Even though crocodilians have been around for millions of years, and as important as these creatures may be in the systems they occupy, they are a much understudied species," says Leslie.

Poaching, habitat destruction and contamination have already pushed to the brink of extinction the Indian gharial, Orinoco crocodile, Cuban crocodile (photo), Siamese crocodile, Chinese alligator and the black cayman but in fact, all crocodilian species are now very vulnerable. Global warming threat would be just an added kick to their end ...