Bearded dragons can change the color of specific body parts to help regulate their body temperature and to communicate with others, according to a new study. A darker backside, for example, keeps them warmer in cool weather, while different neck colors act as signals to other lizards. The findings are published in Proceedings of the Royal Society B this week.
Many lizards can change colors rapidly for a variety of reasons, ranging from camouflage to communication. But it’s unclear if and how they manage all of these different functions (and colors) at the same time.
To investigate, University of Melbourne’s Kathleen Smith and colleagues observed 12 male central bearded dragon lizards (Pogona vitticeps) captured from north of Walpeup, Australia. These lizards showed the greatest color change in response to temperature on their back. By contrast, they showed the greatest color change unrelated to temperature on their throat and upper chest – changes that occurred during social interactions. The team tested the lizards for 45 minutes at 15 and 40°C (60 and 104°F), temperatures they’d normally experience in the wild. You can see photos of the same lizard at the two temperatures below.
The same lizard at 15°C (left) and 40°C (right). Kathleen Smith/University of Melbourne
To maintain their ideal temperature of 35°C (95°F), “a bearded dragon can change its back to a light yellow color when it is hot to a dark brown color when it is cool,” Smith said in a statement. They do this quickly too, which suggests that it’s an important adaptation. After all, a cold lizard is a slow lizard.
Darker colors allow more of the sun’s energy to be absorbed. Having dark colors on their back could reduce the time it takes to reach an active body temperature by 22 minutes a day on average – saving 85 hours of basking time during breeding season. While their beard and upper chest colors don’t respond to temperature, these did change dramatically from cream to jet black during social interactions in the breeding season. This color change was accompanied by head bobs, push-ups, and arm waving – signals of social dominance. That means bearded dragons can partition color change on different body parts for different purposes.
“A bearded dragon lizard can balance all of its color change requirements by only changing color on the back for regulating temperature (which appears to be beneficial as it is exposed to the sun), and only changing the beard/chest color for social communication (which is the region displayed to other lizards)," Smith added.