Bearded dragons can change their spots

Bearded dragon lizards can change the colour of different body parts for different functions.

A breakthrough in the study of bearded dragon lizards has progressed the study of many lizard species. Researchers have discovered that the lizards can both respond to temperature variations and send each other social signals – by changing the colour of different parts of their body.

Deakin University’s eminent evolutionary biologist, Professor John Endler, undertook the project with colleagues from the Universities of Melbourne and Wisconsin. The researchers observed 12 wild-caught bearded dragons at different temperatures and during social interactions in the breeding season in northern Victoria.

They discovered that colour change in the neck area was only linked to social interactions with other bearded dragons. However, the backs of the lizards become darker in cool weather – saving approximately 85 hours of basking time during the energy-intensive breeding season.

The findings were recently published in the prestigious journal,“Proceedings of the Royal Society of London B.”

[testimonial_text]No one has researched simultaneously both the colour changes for thermal regulation and social interactions in lizards before. All lizards change colour and use visual displays, so it is very likely that similar abilities could be found in many different, and possibly most, lizards.[/testimonial_text]
[testimonial_picture name=”Professor John Endler” details=”School of Life & Environmental Sciences”]

Professor Endler is a world expert on the co-evolution of animal sensory capacities and colour patterns. He has studied such phenomena in fish, insects, birds and frogs, also attracting international interest for his discovery that great bowerbirds use optical illusions in their bowers to attract mates.

The bearded dragons were photographed during exposure to temperatures of 15 and 40 degrees Celsius, and the levels of light reflected from the lizard’s skins recorded. By changing to a darker colour in the cooler temperature, the bearded dragons reflected much less light than the paler lizards, reflecting only 8% of light, compared to 23% reflectivity from the paler lizards.

“The darker lizards would heat up to their active state, on average, 22 minutes earlier, thereby allowing them to move away from predators sooner,” Prof Endler explained.

The project leader, Melbourne University’s Katie Smith, added that the ideal internal body temperature for a bearded dragon lizard is 35 degrees Celsius.

“In order to maintain this temperature, a bearded dragon can change its back to a light yellow colour when it is hot or to a dark brown colour when it is cool,” Ms Smith said.

“The chest and beard do not change colour in response to temperature, but change dramatically from cream to jet black during social interactions, accompanied by head-bobs and push-ups.”

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