Dad lizards make better mothers - it is an odd finding, but one that appears to be true, according to a new study on bearded dragons.

Researchers from the University of Canberra have found that bearded dragon lizards can change gender in the egg.

And curiously, animals that change from male to female tend to make better mothers.

The phenomenon is known as sex reversal, where an animal's chromosomes - and what they look and act like physically - do not match up.

It means male lizards act as females, as explained in new findings published in the international journal Nature.

"So your genes are telling you that you should be a male, but you're actually living out your life as a female," Dr Claire Holleley, from the University of Canberra, said.

Researchers studied 131 adult lizards, using controlled breeding experiments.

"They reproduce, and are completely functional females," Dr Holleley said.

"The bearded dragons are the first species where we've actually been able to demonstrate this genetically.

"This is the first time ... in a reptile, that we've actually found and established that sex reversal happens in the wild."

Climate change 'could play a role'

Dr Hollely said it was believed a type of skink also experienced the phenomenon, and it also happened in fish.

She said the cause for the confusion was heat.

"When you're developing in the egg, there's a period of thermosensitivity in the middle of the incubation," Dr Holleley said.

"If you get exposed to a hot temperature during that period of sensitivity, that's what causes sex reversal in these animals.

"It triggers the loss of their sex chromosome - the equivalent of losing the [male] Y chromosome if you're a human.

"What we showed was how a system can go from a predominantly genetic mode of sex determination, using sex chromosomes to determine whether or not you're male or female, to a system where incubation temperature, without sex chromosomes at all, determines sex."

Dr Holleley said the most interesting and unexpected finding from this work was that sex-reversed females appeared to be more fit than regular females.

"If you're a he-she animal - with male sex chromosomes, but reproducing as a female - you actually laid almost twice as many eggs as a regular female," she said.

"Basically, dads make better mums."

Dr Holleley said climate change could be playing a role in the process.

"We did notice over the course of the study that the rate of sex reversal is increasing," she said.

"Whether or not this is due to an increase in global temperatures is something we have to pin down in future research."