The Puerto Rico-living white-lip anolis have developed a sophisticated communication system. Photo: Terry Ord
Reading Lizards announce important messages with the help of their eye-catching throat pack. Through this signal, they attract the attention of their conspecifics and only then begin with the transmission of the actual message. The animals observe their surroundings: only in the case of disturbing environmental influences do they use their throat folds in order to stand out from the interfering signals. The biologists Terry Ord from Harvard University and Judy Stamps from the University of California at Davis have found this out with the help of specially designed robotic lizards. The white-lipped anise (Anolis gundlachi) living in Puerto Rico communicate with their conspecifics only via visual signals. The males use a typical movement pattern for this type: It consists of push-up-like rocking movements of the body and nodding. The males use this body language to alert counterparties to their territory and to attract females. To achieve the attention needed for silent communication, the male animals can set up a colored cleft palate, explain the biologists. So far, an introductory alarm signal was only known from birds, says Terry Ord.

Unlike in animal auditory alarms, American biologists have not been able to use animal sounds to study the behavior of lizards. The researchers therefore used lifelike reproductions of the animals, with which they could imitate the body language of the natural role models. To do this, they programmed motion sequences that were then executed by the artificial lizards. The repertoire of the robot includes seesawing with all four legs, as well as setting up a yellow throat fold.

The researchers noted more than 300 reactions of the real lizards on their mechanical conspecifics and found that both the Kehlfalte and the typical rocking motion is only used in low light or distant conspecifics. The speed of the robot movements also had an effect: the faster the robot rocked and set up its throat fold, the faster the competitors oriented themselves in the direction of the robot. Ordinarily, the faster movements are not typical of the lizard species, however. The animals responded to what underpinned the scientists' thesis that any quick movement can attract attention.

Terry Ord (Harvard University, Cambridge) et al .: PNAS, Vol. 105, p. 18830 ddp / Stefan Pröll advertisement


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