Female Oz lizards literally turn their backs on mates to avoid sex

lizardMelbourne, Apr 30 : Females of an Australian species of lizard rely on testosterone when they want to put off a male from copulating with her, according to researchers at University of Melbourne.

Evolutionary ecology Dr Devi Stuart-Fox of the University of Melbourne, and colleagues studied the female Lake Eyre dragon lizard (Ctenophorus maculosus) and found that she displays a bright orange belly and throat during parts of her breeding season, which researchers think is driven by the hormone testosterone.

They found that the colour features prominently when the female wants to keep amorous males off their back.

The researchers examined female lizards taken from Lake Eyre in South Australia and observed what happened when they were in the company of males.

When lizards copulate, the male bites the female''s neck, climbs on top of her, wraps his tail around hers and inserts one of his two penises.

This can be dangerous for females because when the males bite them on the neck, this can pierce the female''s spine and result in death.

Therefore, once the female''s eggs have been fertilised, she will try to avoid mating. However, males don''t give up easily.

"The males are really persistent. They try and force copulation and they harass females all through the breeding season," ABC Online quoted Stuart-Fox as saying.

Unreceptive females drive away advancing males by taking on a threatening posture and if that doesn''t work, they throw themselves on their backs and reveal their bright orange underside.

"Males can''t actually force themselves onto a female when she''s on her back," said Stuart-Fox.

The researchers also measured the levels of sex steroids in blood samples taken from the lizards over time and found that progesterone and testosterone usually decreases once female are no longer receptive to mating.

"They maintain high testosterone levels all through the reproductive cycle including when they weren''t receptive later in the cycle," Stuart-Fox said.

According to researchers, the testosterone is used to drive the female courtship rejection behaviours.

The findings have been reported online ahead of print publication in the Journal of Comparative Physiology. (ANI)