Like many reptile species, tuatara hatchlings aren't born a specific gender just because of their DNA. Instead, the temperature of a nest determines the sex of the eggs that hatch in it.

But unlike many reptile species, which produce more females when the nests are warmer, tuatara eggs tend to hatch more males when temperatures rise.

According to a new study, this means that that warmer temperatures caused by global warming will unfairly skew tuatara populations toward the male gender in just a few decades, and ultimately doom them to extinction.

Direct descendents of the dinosaurs, only two tuatara species remain (Sphenodon punctatus and Sphenodon guntheri) in existence in New Zealand, where they live on just a few small islands off the country's coast. Their habitats offer few opportunities to move to cooler areas. The population on North Brother Island is already male-heavy, although scientists don't know yet if this gender imbalance has been caused by climate change.

Story by John Platt. This article originally appeared in Plenty in July 2008.

Climate change could kill off the tuatara
Rising temperatures affecting tuatara populations.