Indian rock agama (Psammophilus dorsalis)

Hampi is a UNESCO World heritage site in Karnataka, India. It was once the centre of the Hindu Vijayanagara empire but today exits as a collection of thousands of temple ruins, interspersed amongst granite outcrops and boulders – some of the oldest rock on Earth! I was there to sample the area’s bouldering and between doing that, escaping hordes of western travelers trying to find themselves, and evading locals determined to clean my ears out with a small spatula, I often stopped to watch a well camouflaged lizard, the Indian rock agama.

The Indian rock agama (Psammophilus dorsalis) is a diurnal lizard ranging across South India’s hilly regions, where it can reach high densities of up to 90 individuals per hectare. Females and juveniles tend to have brown colouration with speckles and cream blotches, males are larger and develop bright colours in the breeding season.

These lizards have a complex array of signals that they use to communicate with each other across their habitat. Some research was conducted to investigate the signals used by the lizards – trying to learn the lizard language.

The lizards display head bobbing, push ups, dorsal flattening, tail raising and arching of the back. What is interesting though is the use of the signals by males and females in different contexts. For example, both males and females show push-up displays (though males usually do double push-ups, females single ones) whereas only females display tail raises. In addition, the stimuli that elicit the signals are also different for males and females. Males deliver back arching displays in response to the presence of monkeys or squirrels, while females arch their backs in response to male presence.

The authors speculate that morphological and behavioural differences between the sexes can potentially explain these differences. Males have a thicker tail base, making tail raising difficult for them. Females lack the dewlap (throat pouch) so are obviously unable to perform signals using this. Males flatten themselves in response to birds whereas females arched their back. This can be explained by the fact males tend to perch much higher than females and so are at higher risk of predation from birds circling above. Females are more likely to be attacked from birds on the ground so making themselves look larger is the better defence.

Another study looked at whether flight distance (how close you can get without the lizards running away) changed when approached directly or tangentially and while gazing at them or not. They found the flight distance was greatest when the researchers approached directly and while gazing at them. They also mentioned that the females displayed a tail raise to the approaching researchers, but males didn’t.

With a bit of luck and practice, hopefully one day I can be fluent in the lizard language!

Quick facts

• Native to southern India.
• Has a complex ‘language’ of signals which differ between males and females.
• Flight distance increased when gazing at the lizards and directly approaching them.

Further reading:

• Radder, R. S., Saidapur, S. K., Shine, R., & Shanbhag, B. A. (2006). The language of lizards: interpreting the function of visual displays of the Indian rock lizard, Psammophilus dorsalis (Agamidae). Journal of ethology, 24(3), 275-283.
• This is the main paper from the tale. The paper reads well and they go into the different kinds of signals they quantified after watching the lizards. Their study site was in Hampi and after marking the lizards by clipping toes they marked down their behaviours and other animals in the area etc while watching them in 30 minute sample sessions in the morning and afternoon.
• Sreekar, R., & Quader, S. (2013). Influence of gaze and directness of approach on the escape responses of the Indian rock lizard, Psammophilus dorsalis (Gray, 1831). Journal of biosciences, 38(5), 829-833.
• A really neat little study on the flight distances of the lizards. They spotted lizards with binoculars before approaching them either directly or tangentially (5-8 degrees) and while maintaining gaze or looking over the shoulder away from the lizard. They found that the shortest flight distance (i.e. the closest you can get to the lizard) occured when they approached tangentially and without gaze, the longest was directly and maintaining gaze.