An obsession with desert reptile kept zoologist on the run
Dr Li Chunwang's reptilian friend played this game before, but it still wasn't going to miss a chance to stretch its legs. The palm-sized steppe toad-headed lizard, Phrynocephalus frontalis, has kept Li busy for more than five years in the lead-up to a research paper he published this summer. In his laboratory, he places a small plastic cage in front of a 1.5-metre long, 10cm-wide enclosed path of sand. The door opens and, after a moment, he darts out like an arrow. It's over in a flash, but the results are fascinating.
You have spent years studying the steppe toad-headed lizard. Why?
As an animal behavioural biologist doing most of my field work in western China - a poor, dry and sandy region with a fragile ecosystem- I came across many eye-catching species, including the beautiful, but almost extinct, Przewalski's gazelle, the Mongolian wild ass and the popular but much-hated field mice. I can easily get funds to study these animals, as long as I tell people how dire their situation is, how soon they will go extinct or, in cases such as with the mice, how threatening they would become if left unstudied.
But every species is equal. Every animal has its own unique and irreplaceable role in an ecological system that, only when pieced together, can paint us an accurate picture of what has gone wrong in a region and what should be done to restore its health. The steppe toad-headed lizard is an example of our carelessness in regard to common species. They have done well, suffering little from human activities, and therefore they can't win much sympathy without a sad story to tell. So even though the lizards run under the nose of scientists every day, we know shamefully little about them. We don't know, for instance, their total population, how they form their communities, or how they have sex. We don't even know how long an individual one can live.
The neglect of one of the most successful species in western China made me extremely uncomfortable. The lack of a clear understanding about their function in the ecological system puts our studies on bigger animals, such as rodents and gazelles, on shaky ground.
Why did you decide to begin with its running?
To animal behavioural scientists, running is the apex of millions of years of evolution. It requires the maximum level of co-ordination among limbs, at top speed it represents a species - it's the ultimate survival skill. One mystery is how fast it can run. It is much faster than geckos and even capable of keeping giant pursuers, including people, at bay. But no one knows for sure their top speed. However, a more intriguing question is what determines their running speed.
What did your experiments find?
A big surprise - something never reported before. Lizards, unlike birds and mammals, run with cold blood, and according to previous studies, they can sprint only when it's neither too hot nor too cold. That is a dominating factor, and it is also the case for steppe toad-headed lizards. But what surprised us was the second most important factor that determines their running speed: the size of sand grains. The sand affects their top speed, even when the temperature stays constant.
When the sand grains are too big, the lizards falter. When they're too small, their feet sink too deeply, causing a sharp loss of momentum. Only when the grains of sand are within 0.5 to 1.0mm in diameter will the lizard be able to reach top speed and catch a resting bug or evade the claws of an eagle. The lizard sheds new light on our understanding of the running behaviour of reptiles. Previous studies all tried to identify the second most important factor by looking into its anatomy such as the length of the tail and comparing their sizes, but no one paid attention to the sand under their feet.
How did you carry out the experiment?
We captured 14 adults, six males and the eight females that weren't pregnant, from the Hunshandak desert of Inner Mongolia in the summer of 2008. To recreate the natural environment in our labs in Beijing, we brought back sand and sifted the grains into different size groups. We attached a digital video camera to capture the time and distance of a lizard's movement. To get the most accurate results- and in compliance with the academy's ethnic ethical guidelines on the treatment of animals in experiments- we rested each lizard for more than 10 minutes between runs. At the end of the experiment, all lizards were sent to the Beijing Zoo. During their stay in our lab they became our friends, feeling so secure and comfortable that they didn't instinctively flee their cages after the door was opened. That gave us some trouble, but it was the only problem we had, and we easily solved it by using a paint brush to tickle them.
What is the significance of your findings?
Running plays an important role in the lizard's struggle for survival. When compromised, it can lead to starvation or death. Therefore, the species tend to avoid regions with healthy and thick foliage. They also rarely live in completely deserted areas where there is only very fine sand. The sand they like is typical in areas of mild desertification. That led us to propose that the appearance of the lizard population in a region indicates a dangerous tendency towards total desertification. Not everyone has access to high-definition satellite images of a region, but any herdsman or peasant can recognise the steppe toad-headed lizard.
How did you catch them in the wild?
We didn't need to travel far from a town to find a thriving colony. All we needed to do was pull over on a desert highway, walk inland for about three or four kilometres... They were everywhere... But even to experienced lizard hunters like me, they often won in a race of pursuit, as they not only run fast but also change course suddenly. We could have easily captured dozens of them by digging up their shelters, but we would have destroyed their habitat. So we used our hands. Capturing them was very labour-intensive work, especially after a few hours in the sun.
