Dragons lead a colourful life
Bearded dragons can blend into the background, as long as it's the right sort of background. Andrew Masterson reports.
Bearded dragons from Mildura, in the Australian state of Victoria, can turn a very fetching shade of yellow, while members of the same species from Alice Springs, 1,700 kilometres further north, much prefer to look orange.
Those are the findings from research into the ability of the iconic Australian lizard to blend in with its surroundings.
The study, published in the Journal of Experimental Biology, found that each reptile’s colour-changing ability was determined by where it lived.
The bearded dragon (Pogona vitticeps) is one of the most widely distributed and familiar Australian lizards. It has long been noted that they are able to change their body colour, the better to blend with surroundings, but the nature and extent of this ability had never been studied.
To investigate, a team led by Viviana Cadena from the from the University of Melbourne captured wild males from the extreme edges of the species’ natural range and installed them in terraria in the university’s School of Biosciences.
The scientists then observed the colour change in the animals when they were exposed to three different backgrounds: yellow, to simulate the sandy soils of the Midura region; orange to match the darker soils of Alice Springs; and black, as a reference.
The team found that all the dragons changed colour in response to background, but that they were much better at mimicking the tints and tones of their usual habitat. The findings suggest that the dragons’ camouflage range developed over the long-term, and is not able to adapt well to short-term changes outside the palette found in their own territories.
However, the researchers add in their paper, back in their native deserts, the bearded dragons might well display faster and more pronounced colour changes than those observed in the lab.
“The prolonged time in captivity on a single visual background in the absence of natural predators, and the absence of any threat during experiments, may have dampened anti-predatory responses, which might be more pronounced in lizards in the wild,” they write.