A team of Australian and South African researchers has found some male Augrabies flat lizards delay the onset of vivid colouration, which exposes their masculinity at the onset of sexual maturity.

The lizards, Platysaurus broadleyi, are found in South Africa's Augrabies Falls National Park in the Northern Cape Province.

Australian National University Associate Professor Scott Keogh, of the school of botany and zoology, said as soon as the reptile's bright colours appeared, ''the big males would chase them off or beat them up''.

''There's a period of time when they basically pretend to be females and happily walk around the territories of a dominant male,'' Professor Keogh said.

''The male will even try to court them because he thinks that they're females.'' The scientists observed the ''she-males'' had freedom of movement in the normally treacherous zones which were home to aggressive males with fighting experience. The she-males also had access to the myriad females in residence.

Associate Professor Martin Whiting, of the University of the Wit-watersrand, in Johannesburg, said the lizards that delayed the onset of colour to a more convenient period were ''making the best of a bad situation''.

The scientists also examined whether the she-males could mimic the chemical signature or smell of the females. But they found the big lizards were not so easily fooled when it came to smell.

In an experiment performed in the wild, the researchers removed the pheromones and skin lipids from the lizards that might signal what sex they were. They relabelled a group of lizards with either male or female scent, before presenting them to typical adult males.

Males used their tongues to sample chemical scent and responded by courting she-males labelled as females, but not she-males labelled as males. Professor Keogh said the young males appeared to know how the males detected them when they stepped on to rival territory.

''They work very hard to stay just out of smell range of the male,'' he said.

''The male will try and court them, but they try to stay a good 30 or 40cm away from that male to make sure he can't smell them. Because they know as soon as he gets a whiff then they're in big trouble.''

The she-males are also sneaky in their courting habits as they try to seduce the females in front of the dominant male. Males generally court the females by bobbing their heads, but the she-males were careful to keep their head bobbing subtle.

''Lots of times there'll be dozens of females sitting very close to each other. So these young males can just sneak right in and sit right amongst all the females, without being noticed by the big male,'' Professor Keogh said.

The findings are published in the Proceedings of the Royal Society of Biological Sciences.