The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 28, Number 10; October, 2001

Researchers in Australia have found that female lizards can manipulate the sex of their offspring by controlling their body temperature.

From Allen Salzberg, Herp Digest, Vol.2, No.1, August 26, 2001.

One kind of lizard, found in the semi-alpine areas of New South Wales, produced mostly males when they were incubated at 30°C. However, they produced an equal number of males and females when they were incubated at 25°C.

A similar phenomenon has been noted in egg-laying reptiles, such as crocodiles, where an offspring's sex is determined by the temperature of the nest in which it develops.

But scientists did not expect to find the same thing happening in a species which produces live young because reptiles keep their body temperatures fairly constant.

Ph.D student Kylie Robert and Associate Professor Michael Thompson, of the University of Sydney's school of biological sciences, found in an all-female laboratory population of the water skink, females kept their body temperatures at 32°C and produced only males. In the wild, male and female water skinks are born in roughly equal numbers.

Ms. Robert said that, in the laboratory, the female skinks might have noticed the lack of males and, whether consciously or unconsciously, produced all-male offspring to balance the sex ratio.

Her research is published in the international science journal Nature. Ms. Robert said it is unclear how wild female skinks could "select" a body temperature that would make them produce equal numbers of each sex.