But such fluctuations do not suggest that the skink population is in imminent danger.
"Whether there will end up being so many daughters that it causes damage to the species is extremely hard to tell, because even with warming there could be the occasional cold year that yields sons," Wapstra said.
Among reptiles, it is common for one male to breed with multiple females. This makes the number of available females the factor that ultimately limits the overall size of the population. So it's possible that more females could mean more skinks in general—at least for the immediate future.
However, there is a considerable caveat that warming might also cause the food web the reptiles depend upon to collapse, Wapstra warned.
Evolution at Work
Evolution could also disrupt the trend of temperature-driven gender.
A mutant mother that produces sons at higher temperatures or gives birth to offspring that aren't influenced by temperature might appear, experts say. The offspring of such a mutant would quickly come to dominate the population.
The only question that remains is whether evolution would work fast enough to keep pace with rapid climate change.
(Related: "'Virgin Hatching'? Komodos Born Despite No Male" [February 8, 2008].)
Allison Alberts is director of conservation and research at the Zoological Society of San Diego.
"It has been suggested that species for which the sex of the offspring is determined by the environmental temperature could be seriously affected by global climate change," Alberts said.
"This groundbreaking study is the first to demonstrate that such fluctuations actually occur in nature over many years," she said.
"The impact is likely to be most severe for short-lived species and those that are unable to compensate for rising temperatures by changing their … behavior," she added.
"In extreme cases, the extinction of local populations could be the unfortunate result."
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