Communication Signals in Lizards

Abstract

Charles Carpenter is professor of zoology at the University of Oklahoma and University of Oklahoma Biological Station, Norman 73019, and curator of reptiles at the Stovall Museum of Science and History. He holds a B.A. degree from Northern Michigan College of Education (now Northern Michigan University), and M.S. and Ph.D. degrees from University of Michigan. He is the recipient of many research grants and several awards, including the Distinguished Alumni Award from Northern Michigan University in 1972, and the Regents' Award for Superior Accomplishment in Research and Creative Activity in 1980. Dr. Carpenter holds memberships in many professional and honorary societies and has held offices in several of them. Since 1947, Dr. Carpenter has authored or coauthored over 100 publications. lhe males of some, probably many kinds of lizards, fight together from rivalry. Thus the arboreal Anolis cristatellus of South America is extremely pugnacious: During the spring and early part of the summer, two adult males rarely meet without a contest. On first seeing one another, they nod their heads up and down three or four times, and at the same time expanding the frill or pouch beneath the throat; their eyes glisten with rage, and after waving their tails from side to side for a few seconds, as if to gather energy, they dart at each other furiously, rolling over and over, and holding firmly with their teeth. Charles Darwin, Descent of Man (1871). The nodding of the head and expansion of the throat pouch by these male lizards may not have been recognized by Darwin as their manner of communicating with each other. I will relate my experiences to show that lizards do communicate with each other by using pushups and head nods and that each species does this in its own way, conveying different types of information. I first became aware of these visual signals while observing a population of fence lizards (Sceloporus undulatus) on the shore of Lake Texoma near the University of Oklahoma Biological Station. The males of this small species performed pushups from the knobs on logs and raised areas along a beach. Each time they performed, the same pattern of pushups was repeated with the same rhythm. Each male performed or signaled in his own territory so that he was visible to other males in their respective territories. Thus it appeared that each male was using the same pushup pattern to communicate to males in adjacent territories his claim to a certain area (Carpenter 1962). During the following few years I acquired different species of iguanid lizards from throughout the Southwestern United States. These were placed in large outside enclosures where they could readily be observed and their behaviors recorded on motion picture film. The males of these different species quickly adapted to these enclosures, set up dominance hierarchies (in lieu of territories), and actively displayed at one another as they would from a territorial lookout. In every instance, each species performed with a different pattern of pushups or head nods which indicated to me that each species had its own set of visual communication signals or language (Carpenter 1967). Over the next ten to fifteen years, with the help of a number of graduate students, it was established that every species of iguanid and agamid lizard for which we obtained data had its own species-specific display-actionpattern (pattern of vertical movements through time). It has not been possible to observe all of the species of these two closely related families of lizards because they are too numerous. The Family Iguanidae ranges all over the Western Hemisphere and its nearby islands, with a genus on the Fiji-Tonga Islands and two genera on Madagascar, while the numerous species of the Agamidae complement this distribution, being found in the Old World from Africa to Australia. However, we have observed representative species from all