What goes on in the mind of a lizard?

Every now and again we wonder what our companion cats, dogs, birds and reptiles are thinking as we watch our family pets interact in amusing ways with the world. While we love to interpret their antics through a human lens, it’s the evolutionary biologists and their scientific insights that give it perspective. 

Lizards like bearded dragons make great pets as they are quite ‘relaxed’ in the company of humans and not as skittish as other species of lizards. They sometimes bob their heads, appear to wave their arms, but change colour depending on their surroundings and also their activity. 

They are a little bit like a mood ring.

Vivana Cadena is a research fellow who works in the Devi Stuart-Fox laboratory at the University of Melbourne’s Department of Zoology.

“Bearded dragons change colour for three main functions,” she says, “namely to communicate with each other, to regulate their body temperature, and to camouflage themselves to avoid being spotted by predators like eagles. Their colour ranges from light colours to dark tones, and we have also noticed a colour change according to the daily cycle. They start the day off darker and get lighter as they get active.”

“Although moving in and out of the sun helps them regulate body temperature they also use colour change to help fine-tune their temperature, using lighter colours to reflect the heat when its hot and darker colours to absorb more heat when it’s cool. This fine-tuning of temperature control means they don’t have to spend energy regulating their temperature behaviourally and they can save that energy for other activities like looking for a mate or defending their territory.

“Male bearded dragons communicate to other males who intrude on their territory by flaring their beards which turn black, as does the chest. They also do this when courting a female. They often stand quite high to show off the body and bob the head as a sign of dominance. It’s quite an elaborate display. The females will usually wave their arms as a way of saying ‘Okay I’m your gal’.” 

Ms Cadena says her research has applications not only in animal care, conservation genetics and ecology, but is also of interest to engineers in the design of new fabrics and materials that could change colour. 

Psychologists often refer to our human brain as having a reptilian section that is related to basic instincts of safety and survival. These include, eat, don’t get eaten, hide or attack if required, attract mates, scare off competitors if required, and mate. But what must our lizard pets think of us humans? 

“One thing I do know is every time I walk into the animal house where I have my 30 bearded dragons they all run to their food bowls. They have learnt I am the source of live crickets and it might be time to eat,” Ms Cadena says.

www.zoology.unimelb.edu.au