Australasian Science: Australia's authority on science since 1938

Colour-changing dragons to reveal their secrets

By Tim Thwaites

A study of why animals change colour could enable scientists to develop bandages that change colour in response to slight changes in the temperature of the wound.

Devi Stuart-Fox is attracted to show-offs. “I’m just really fascinated by animals with fabulous colours and ornaments.” And ever since she was a teenager living in a bushland setting in an outer Brisbane suburb, she has also been delighted by lizards. She used to keep them as pets.

Now a senior lecturer in zoology at The University of Melbourne and an Australian Research Council (ARC) research fellow, she has made a career out of it. Her work on colour in lizards and birds has led to significant findings in evolutionary biology. She showed, for instance, that the remarkable ability of chameleons to change colour evolved not as camouflage, but as a social and territorial display. And she has provided the first evidence to support the long-held view that the level of colour variation within species is directly related to the creation of new species.

Now, she has been awarded a $470,000 grant by the ARC to lead an international research initiative using Australian bearded dragons to delve further into how and why animals change colour—and what it costs them.

On the practical side, she has been collaborating with a group in CSIRO who are particularly interested in materials that change colour in response to heat. Such materials can be used, for instance, to produce bandages that track how wounds are healing.

Ten years ago Devi’s early career received a boost when she received a UNESCO- L’Oréal International Fellowship to study chameleons in South Africa. Last week in Paris she received the mid-career L’Oréal-UNESCO International Special Fellowship “... in the footsteps of Marie Curie”. This honour is awarded annually to a woman researcher who, in the 10 years since receiving an early-career fellowship, has demonstrated excellence and determination in her pursuit of a career in research.

The US$40,000 that comes with Devi’s Special Fellowship will help her further her work in an unusually productive way. Her research has by no means been Devi’s only achievement of the past 10 years. She and her husband Adnan Moussalli are raising a family of two children. The money will smooth the way. He is also a biologist, currently studying Australian land snails.

“One of the limiting things for me at the moment is that I don’t want to spend extended periods away from my family. The only way I can juggle that is to take my family with me into the field. The award will help give me flexibility to do that. My husband and I can often manage to combine our field work so that we catch snails and lizards in the same place.”

Although she has accomplished so much, Devi says she views most of her career “as accident and circumstance”. For the most part, she says, she has simply followed her interests. Clearly it has been serendipity of which she has taken great advantage.

The daughter of a historian, initially Devi wasn’t sure she even wanted to pursue science. So she hedged her bets and started an Arts/Science degree at the University of Queensland. She was persuaded onto the road she has now taken by a couple of inspiring lecturers in zoology. In particular, Prof Craig Moritz, now an ARC laureate fellow at the Australian National University, sparked an interest in evolutionary biology which has never waned.

Even so, after her undergraduate degree she took a year out to work and travel. And when she couldn’t find anything in the hospitality industry, she took a job looking after a private reptile collection and showing off its members to school children in shopping centres. ‘Experience with venomous snakes necessary,’ the advertisement had read. “I fronted up and told them that while I had no experience with venomous snakes, I wasn’t scared of them. I don’t think anyone else applied.”

When she finally returned to the University of Queensland to undertake her PhD, she knew she wanted to work with live reptiles—and preferably colourful ones. “Australia doesn’t have many colourful reptiles. They’re all brown because it’s a brown continent.” She ended up investigating the evolution of colour variation in tawny dragons and red-barred dragons, some of the most colourful lizards the continent had to offer. As part of her studies Devi set up a database of the worldwide family to which the dragons belonged.

She was looking for a link between species richness and sexual differences in size and colouration. And while the Australian representatives of the dragon family were relatively drab, their closest relatives, the chameleons, definitely were not. So she applied and was accepted for a post-doctoral fellowship at the University of the Witwatersrand in South Africa. And that’s when she won her first L’Oreal fellowship. “The post-doctoral fellowship only paid my salary. The L’Oreal fellowship paid for my research costs.”

It was a good investment. This was the work which not only showed that the real impetus for colour variation in chameleons was not camouflage, but signalling, and it was also where she began to develop many of the ideas and approaches to her research. For instance, she became aware that it is not important how chameleons look to us, but what another chameleon or a predator sees. And both chameleons and their predators can detect colours that humans cannot, such as in the ultra-violet. So her measurements and her models of animal colour communication needed to take that into account.

She and her husband were able to compare the colouration and ability to change colour of 21 groups of southern African dwarf chameleons; how they reacted to males and females of their species; and how they reacted to predators such as birds and snakes. They found the greatest range of colours was exhibited in aggressive male flashing contests, often contrasting rather than blending with background vegetation.

That taught her a lesson she has never forgotten. “Things aren’t always as they seem.” In a more recent project studying Lake Eyre dragons in the middle of a central Australian salt pan, Devi found, unusually, that it was the female lizards that were most highly coloured. To prevent mating attempts by sexually aggressive males, they flip over onto their backs, exposing bright orange patches on their undersides.

You would think this signal would attract predators, but no, says Devi. First, there are few predators on a water-scarce salt pan. Second, the predators that are present are so unused to such a bright colour, “they don’t even recognise the flipped-over lizards as prey”.

Having established her work in the realm of lizards, Devi soon recognised that one of the basic evolutionary questions to do with colour would not be easily answered using her favourite animals. For more than 50 years evolutionary biologists have proposed that the more colour forms that coexist within a single species, the quicker it evolves into new species. Although this seemed to be true, no biologist had been able to accumulate enough data to support it definitively.

“The best known group of animals in terms of natural history is the birds—and we also have a lot of genetic information about them.” So Devi and postdoctoral researcher Andrew Hugall confirmed the link in three worldwide families of birds of prey — the hawks and eagles, the owls and the nightjars. They published their results in one of the world’s most respected science journals, Nature. Devi is now furthering that work by investigating colour variations across the range of Australian tawny dragons.

She is also studying the mechanism of colour change in bearded dragons, but this time going into the near infrared. These are wavelengths of radiation associated with heat rather than colour and are generally unable to be detected by other animals except snakes with special heat-sensing pits. “These wavelengths may be significant due to their effect on the lizards’ thermal balance. And we now have access to a machine which can measure reflectance of radiation in the near infrared.”

It turns out that bearded dragons change colour in response to heat—they are thermochromic. And that’s of great interest as a natural model to a group of CSIRO materials scientists led by Mr Phil Casey. Thermochromic compounds have several applications, including bandages which can track the progress of healing by displaying the temperature changes in wounds.

One of the aspects of her work that Devi likes best is mentoring young researchers, especially young women. “There are several big challenges for women in science. At the psychological level, women need to develop greater confidence in their own intellectual abilities, and men need to accept women as their intellectual equals.

“Both men and women also need to challenge the perception that successful, professional women are somehow less likeable. And at an institutional and structural level, the challenge is to accommodate career flexibility, such as time out for having children.”

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