Bearded dragons are amazing lizards in the genus Pogona. There are eight Pogona species. Researchers in Australia have studied Pogona vitticeps to learn more about how they rely on environmental cues or genetics (or both) to determine the sex of the babies.
Here, a bearded dragon shows its "I'm threatened" display. The mouth is opened, the inside often flushed with orange, the dark beard flares out in contrast, and there can be a hiss. In captivity they quickly become accustomed to human presence, and the display becomes half-hearted, said one of the study authors Arthur Georges, of the Institute for Applied Ecology, University of Canberra in Australia.
Georges and his colleagues incubated the eggs at various temperatures, some of which were warm enough to transform genetic males into functional females, or those that could lay eggs. These babies were considered sex-reversed, because they were genetically males but looked like females and could lay eggs like females. [Read the full story on the sex-reversed bearded dragons]
Bearded dragons like this one have a remarkable repertoire of signals — head-bobbing, arm-waving and posturing.
The researchers examined both physical traits and behaviors of the resulting bearded dragon youngsters. To measure the bearded dragons’ level of activity, the scientists looked at how often the lizards bobbed their heads when inspecting a plastic container. How long it took a bearded dragon to emerge from a shelter into an open area was used as a measure of boldness.
Here, a male bearded dragon sits on one of his favorite perches.
The young lizards are more brightly patterned than the adults, and very curious. How bold they are in terms of investigating new things depends on whether they are male, female, or sex-reversed, the researchers found. [Read the full story on the sex-reversed bearded dragons]
These lizards usually select perches where a hasty retreat is possible if required. But they keep a keen eye on the potential threat, Georges said.
In the early months of the austral spring and summer, the male bearded dragons in particular, rather than being secretive, go to great odds to be conspicuous. They choose a few favorite perches in their territories from which to send signals to other males and, of course, positive vibes to the females (both concordant and sex-reversed).
Female body, male brain
"One of the most interesting aspects is that, under natural conditions, we can see a process producing individuals with the bodies of females but, at least to some degree, with the brains of males," said study researcher Rick Shine, from the University of Sydney’s School of Life and Environmental Sciences.
Here, a bearded dragon shows off his impressive display when threatened.
This bearded dragon, from central Australia, demonstrates how placid the lizards are, and why they make such good photographic subjects and why they are a favored pet worldwide, Georges said.
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A bearded dragon in central Australia. [Read the full story on the sex-reversed bearded dragons]
"One critical question, not addressed in our study, is whether or not the behavioral characteristicsof juvenile dragons — and especially, the differences betweensex-reversed females and concordant females — persist into adulthood," the researchers wrote in the June 9, 2016, issue of the journal Proceedings of the Royal Society B. [Read the full story on the sex-reversed bearded dragons]