The language of lizards: interpreting the function of visual displays of the Indian rock lizard, Psammophilus dorsalis (Agamidae)

Abstract

The first step in understanding any communication system is to document signal diversity relative to the context of signalling (e.g. sex of the signaller and audience). Observation of 30 free-ranging rock lizards (Psammophilus dorsalis) on rock outcrops in southern India over a period of 18 months revealed that these lizards produce a complex array of ritualized signals involving push-ups (headbobbing), dorsal flattening, extension of the legs or gular region, and tail-raising. Push-ups were performed by both sexes, usually after moving from one location to another. Push-ups were rarely accompanied by other postural modifications, and seem to function as non-directed signals. Dorsal flattening was elicited by birds flying overhead, and seems to make the lizard less conspicuous to predators. There was, nonetheless, a strong sex difference in the frequency of this behaviour, because the habitats used by males (open rocks) exposed them to more birds. Males displayed to females by extending their gular folds and arching their backs; other animals (e.g. squirrels, monkeys) also elicited the latter posture from both sexes. Leg extension was observed for both males and females, but in different contexts -males in response to conspecifics, females in response to other animals. Females raised their tails in response to encountering a male. Thus, these lizards have a complex repertoire of postures for predator evasion, for interaction with other species and with conspecifics, and for communicating sex-specific social information about gender (tail-raise) or dominance status (gular extension, leg extension).

Ethogram of courtship and mating behaviour of Sitana cf. ponticeriana (Reptilia: Draconinae: Agamidae) in India

“…Rest behaviours during the courtship were almost similar to other agamid lizards (Pandav et al, 2007;Radder et al, 2006). The display act through dewlap extension/fanning by the male of Sitana cf.…”

“…Though not unique to the species, this act is not well pronounced in other agamids found in this part of the country. Push-up displays by both the sexes have been reported in Calotes versicolor (Pandav et al, 2007) and Psammophilus dorsalis (Radder et al, 2006); however in case of S. cf. ponticeriana, this display was not observed for females.…”

“…Head-bobbing behaviour is well documented in many agamids (Brattstorm, 1971;Pandav et al, 2007;Radder et al, 2006), iguanids (Macedonia & Clark, 2001;Martins & Lamont, 1998;Martins et al, 2004;McCann, 1993) and some of the larger scincids (Done & Heatwole, 1977). If this behaviour does increase visual acuity, then in agamids and iguanids it has perhaps arisen for gaining of better visual information about an intruder in their territory and then over a temporal scale, has developed into the species-specific displays seen today.…”

“…Interestingly, agamid lizards exhibit strikingly colourful visual displays. Along with the genera Calotes (Pandav et al, 2007) and Psammophilus (Radder et al, 2006) from the Indian context, genus Sitana also exhibits colourful courtship acts that are well noticed in the field.…”

Absence of kin discrimination in the hatchlings of a lizard, Calotes versicolor (Agamidae)

“…These lizards orient themselves visually while chemoreception is poorly developed in juveniles (Ammanna, Saidapur and Shanbhag, unpublished observations). The agamid lizards (e.g., Amphibolurus muricatus, Psammophilus dorsalis, C. versicolor) are known to use vision for detection of food, predators, and communication between conspecifics (Husak, 2004;Radder et al, 2006;Shanbhag et al, 2010). Extensive studies on A. muricatus and the iguanid Sceloporus graciosus have revealed that they exhibit push-ups and guiar extensions upon encounter with unfamiliar conspecifics (Martins, 1993;Ord and Evans, 2003;Van Dyk and Evans, 2007).…”