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Vibratory Calls in True Chameleons By Christopher V. Anderson & Kenneth Barnett Citation: Anderson, C.V. & K. Barnett (2003). Vibratory Calls in True Chameleons. Chameleons! Online E-Zine, May 2003. (http://www.chameleonnews.com/03MayAndersonBarnett.html) There are a number of misconceptions regarding true chameleon sound production. Many people, who have worked with true chameleons, have experienced their audible hissing and gaping responses. Some chameleon species however, produce a unique low frequency sound as well. The low frequencies of these calls are barely audible to the human ear, and therefore often go unnoticed by the observer. Additionally, these calls have very low amplitude (essentially - the volume). Due to the low frequency and amplitude of the sounds, humans have been more aware of their vibratory component, rather then the audible component. Such a sound, with a wavelength that is too long for the human ear to detect is referred to as "infrasound." Here we review a combination of published and anecdotal information regarding this phenomenon. Published theories: There is relatively little information published regarding vibratory sound production in chameleons. Most accounts of vibratory sound production in chameleons are the result of anecdotal observations. This, along with the limited amount of scientific study that has occurred concerning this behavior, has lead to many misconceptions and a wide variety of theories about its function. Schmidt1 describes the vocalization of Ch. (Ch.) calyptratus as a defensive sound similar to a hissing or whistling. It is assumed that by this he is referring to the loud hissing and gapping response to threats that are most commonly encountered. He then goes on to describe an observation that he says he has only been able to observe in a limited number of specimens of the species. He describes it as a vibration of the body but believes it to be a high frequency. He then goes on to state, ". . .obviously this is a means of defense against small predators such as ants." He justifies this theory saying that it is an adaptation for sleeping close to the ground. He further states that proof of this is shown by his observation of this vibration when the chameleon is touched while sleeping. Research has since determined that this is in fact a low frequency sound rather than high frequency. Necas2 names more species that make this vibratory sound. He mentions that Brookesia stumpffi, B. superciliaris, Rhampholeon kerstenii and Ch. (Ch.) calyptratus are all known to produce a "weak, low frequency buzzing sound imitating a bee" during handling. Whether Necas was actually inferring that the sound mimics a bee is questionable. It is more likely that he was describing what he viewed as some type of defensive (startle) behavior. B. thieli, B. vadoni, B. legendrei (which has since been synopsized with B. ebenaui), B. stumpffi, B. valerieae and R. kerstenii are noted by Glaw and Vences 3 as producing body vibrations when touched. They state that "the body is strongly flattened laterally and the body produces rapid vibrations," but no mention of the vibrations being a sound is made. They do however recognize it as a defensive behavior. Le Berre4 made one of the first reports of this low frequency sound being more than a defense mechanism.4 He cites Ch. (Trioceros) oweni and Ch. (T.) johnstonii females making "low 'purring' sounds when held by a human or when approached by a potential mate." While he clarifies that it has not been determined if the males can hear these vibratory sounds, his observations gives merit to the possibility that the vibrations are used as a form of communication. Davison5 also indicated that this vibration could possibly be a form of communication. Here she indicates that these vibrations which she also describes as a buzzing, "seems to resonates through the tree" acting as a warning or even threat to other chameleons infringing on their territory. Describing the vibrations as a minor electric shock, Spawls et. al.6 speak of this behavior as well. They mention a number of species that are known to produce these vibrations when picked up: R. boulengeri, R. brachyurus, R. brevicaudatus, and R. kerstenii. They indicate that it is possible that the chameleons produce this vibration by exhaling a small amount of air to startle predators long enough for the predator to drop them. Once the chameleon has been dropped, the cryptic camouflage potentially will cause the predator to loose track of the chameleon and move on. In a study by Barnett et. al.7 the low frequency sounds of Ch. (Ch.) calyptratus were recorded using PCB accelerometers and canary software. They proposed that this vibration was a form of communication whereby the vibrations were transmitted through the branches of trees. The recording device was attached to a branch during courtship and for the first time, the infrasound mating call of the veiled chameleon was recorded. When an adult male Ch. (Ch.) calyptratus was placed in an enclosure with a receptive female, he produced several low frequency calls that were recorded and quantified. Sounds were also recorded from an individual that were elicited from human touch. This is seen as convincing evidence of the use of infrasound vibrations as a method of communication. More recently, in unpublished material, Barnett has video recorded situations where both male and female veiled chameleons produce vibratory calls during courtship. The videotaped sequences also show that the male produces vibratory calls during copulation. Other situation dependent calls have been observed. Barnett has observed Ch. (Ch.) calyptratus chameleons producing low frequency sounds during feeding. Also, on many occasions, when an individual enters the facility where several Ch. (Ch.) calyptratus are housed, male Ch. (Ch.) calyptratus will flex their bodies and produce one long vibratory call. For a behavior that has so many varying theories and accounts behind it, it is remarkable that so little research has been conducted and so little published about it in the past. The behavioral aspects of this sound production could prove very interesting and further research in the area should answer a lot of questions. Theories and current research Current and past research into the low frequency sound production of chameleons is still quite limited. The authors here are in the process of conducting separate research on this topic. We have been corresponding and exchanging ideas for some time now. It is hoped that this research will answer a number of questions and tell us more about these chameleons and there behavior. Our conversations have yielded a number of very interesting theories which we hope to experiment with in the near future. We believe that the function of the low frequency vibration may differ between the subfamilies Chamaeleonidae and Brookesiinae due to different selective pressures over time. The subfamily Chamaeleonidae consists of the genera Bradypodion, Calumma, Chamaeleo and Furcifer. These species are for the most part arboreal. This enables the vibrations to be transmitted through the branches of the tree where other chameleons can detect them. By doing so, communication is possible over what could be a considerable distance and the infrasound vibrations can be used for courtship, territorial claims and other purposes. The subfamily Brookesiinae is made up of the genera Rhampholeon and Brookesia. The members of these genera are generally terrestrial species living close to the ground. While on the ground, transmission of these vibrations through the leaf litter and ground would not travel as far as in a tree because the vibrations will travel in all directions rather than along a particular path in the form of a branch. It therefore seems more probable that this would be used as a defense so that a predator would be startled and drop these little chameleons. We also believe that is it likely that these calls could be used as communication but it would have to be at a much closer range than the members of the subfamily Chamaeleonidae. It is not clear at this time if true chameleons can hear any airborne component of the vibratory sounds they produce. As we know, chameleons have gone through a great deal of evolutionary changes to evolve a complex form of communication in the form of color and pattern changes. What were the evolutionary pressures that would have additionally fashioned a low frequency form of communication in chameleons? The authors have discussed the secretive nature of chameleons, along with their many predators. It would seem logical that these low frequency sounds serve as a form of communication when their primary defense is working. If however their camouflage does fail and they are seen, then their color and body displays can be used. We believe this to be at least one possible benefit of the vibratory system of communication. Many questions remain regarding exactly what type of information is being conveyed. Is it fitness, sex, age, receptivity? If vibratory sound production was important in chameleon evolution, could there be anatomical modifications that either enhance the sound, or improve the reception of such signals? We already know that chameleons have an enlarged pterygoid process in the skull. Wever8 showed that this bone is clearly involved in sound reception. Research still needs to be done that would show if head ornaments or casque size of certain species mediate vibratory sound production in any way. Anderson is in the process of working with the genus Rhampholeon and their infrasound vibrations. For his research he will be recording sounds in the lab produced by various species when they are handled. He will also be attempting to collect recordings of any sounds possibly made when animals are introduced into the established territory of another specimen. In doing so he hopes to record any possible defensive, courtship or territorial sounds produced. He will then use sonograms and oscillograms to compare the sounds. These findings will be compared based on species, sex and stimuli hoping to find some pattern. He hopes to determine if the infrasound vibrations from one species vary based on specimen, sex or the stimulus under which is was recorded. He then wants to see if there are any consistent variations based on species that could potentially be explored as a method of species identification similar to methods used with frog calls. After recordings have been collected in the lab, he will supplement his data with further recordings collected in the wild. These will be used to show whether or not captive specimens from the lab produce consistent patterns in their infrasound vibrations to those in the wild. Once this has been completed, he intends to playback these recordings to various specimens in order to observe any behavioral response. His study on Rhampholeon spp. should hopefully give us great incite into this form of communication and defense. Barnett is primarily continuing his work with Ch. (Ch.) calyptratus. He is currently working in hopes of determining the mechanism by which these infrasound vibrations are produced. Once it is known what structure produces these sounds, closer analysis of various species could potentially allow us to determine which species do or do not produce these calls. At this point, we could also see any evolutionary trends moving toward or away from this form of communication. This could potentially be of great value in the taxonomic grouping of chameleons. By recording which species are known to produce or not produce these vibrations, we may deduce some primary correlation, or lack there of, with current taxonomic groupings (for instance, despite many hours of observations, Ch. (T.) jacksonii has never been observed producing vibrations). Such investigations could add a great deal to our knowledge of chameleon behavior and evolution. The use of infrasound vibrations in chameleons is an aspect of their behavior, which provides many unanswered questions. Past theories and observations do little more than show the need for further study. The research being conducted will hopefully help answer some of these questions in the future. More than likely, however, they will also serve to increase the opportunities for further research in this area. The possible behavioral and evolutionary findings are of great interest and could potentially prove to be very rewarding. Understanding the form and function of vibratory sound in chameleon behavior may also provide some insight into the development of communication systems in other arboreal vertebrates. To discuss infrasound vibrations in chameleons, feel free to contact Chris Anderson (cva3@cornell.edu or parsonii_hoehnelii@hotmail.com) or Kenneth Barnett (kbgecko@aol.com). Any observations that you feel could aid our research are also much appreciated. Our research is being conducted independently of each other but we do discuss information and ideas regarding our theories and ideas. To hear a sound file recorded by Kenneth Barnett of the Veiled Chameleon, click play below.   Species known to produce infrasound vibrations: The following is a list of species reported to produce low frequency sounds. Those that have not been mentioned in the text with their source have been cited following the species account: Brookesia antakarana (A. Beveridge, pers.com.), B. decaryi (E. Edwards, pers.com.), B. ebenaui, B. stumpffi, B. superciliaris, B. thieli, B. vadoni, B. valerieae, Chamaeleo (Chamaeleo) calyptratus, Ch. (Ch.) senegalensis (Kenneth Barnett, pers.obs.), Ch. (Ch.) dilepis (Kenneth Barnett, pers.obs.), Ch. (Trioceros) johnstoni, Ch. (T.) melleri (A. Banks, pers.com.), Ch. (T.) oweni, Furcifer pardalis (A. Beveridge, pers.com.), F. oustaleti (various sources), Rhampholeon boulengeri, R. brachyurus, R. brevicaudatus, R. kerstenii (both R. k. kerstenii and R. k. robecchii), R. spectrum (B. Ikkala, pers.com.), and R. uluguruensis (J. Mease, pers.com.).  1 Schmidt, W. (2001). Chamaeleo calyptratus: The Yemen Chameleon. Matthias Schmidt
Publications, Germany. 2 Necas, P. (1999). Chameleons: Nature's Hidden Jewels. Edition Chimaira, Frankfurt am Main. 3 Glaw, F. & Vences, M. (1994). A Fieldguide to the Amphibians and Reptiles of Madagascar,
Second Edition. M. Vences & F. Glaw Verlags GbR. 4 Le Berre, F. (1995). The New Chameleon Handbook. Barron's Educational Series, Inc.
Hong Kong. 5 Davison, L. J. (1997). Chameleons: Their Care and Breeding. Hancock House Publishers,
Canada and US. 6Spawls, S., Howell, K., Drewes, R. & Ashe, J. A (2002). Field Guide to the Reptiles of East Africa.
Natural World Academic Press. 7Barnett, Kenneth E.; Cocroft, Reginald B.; Fleishman, Leo J. Possible Communication by Substrate
Vibration in a Chameleon. Copeia; 1999(1):225-228. 1999. 8 Wever, E. G. (1978). The Reptile Ear, Its Structure and Functions. Princeton University Press.  Christopher V. Anderson  Chris Anderson is a herpetologist currently working on his Ph.D. at the University of South Florida after receiving his B.S. from Cornell University. He has spent time in the jungles of South East Asia, among other areas, aiding in research for publication. He has previously traveled throughout Madagascar in search of, and conducting personal research on, the chameleons of the region. He has traveled to over 35 countries, including chameleon habitat in 6. Currently, Chris is the Editor and Webmaster of the Chameleons! Online E-Zine and is studying the kinematics and morphological basis of ballistic tongue projection and tongue retraction in chameleons for his dissertation. Chris Can be emailed at Chris.Anderson@chameleonnews.com or cvanders@mail.usf.edu. Kenneth Barnett  Kenneth Barnett is a 44-year-old Pesticide Control Specialist with the New York State Department of Environmental Conservation. An all around naturalist, Kenneth has always been fascinated with animal behavior. Ken’s chameleon observations in the early 1990’s eventually led to the first recordings of chameleon vibratory sounds. Kenneth continues his chameleon studies while conducting wildlife lectures throughout the state. A licensed New York State wildlife rehabilitator and raptor handler, Ken’s diverse background includes stints as an electron microscopist for the Yale University School of Medicine, a horticulturist in a plant pathology laboratory, and salamander field biologist. More recently Kenneth and his wife have been leading tour groups into Corcovado National Park in Costa Rica. Ken can be emailed at kbgecko@aol.com or natureXchange@aol.com. mailto:cva3@cornell.edumailto:parsonii_hoehnelii@hotmail.commailto:kbgecko@aol.commailto:Chris.Anderson@chameleonnews.commailto:cvanders@mail.usf.edumailto:kbgecko@aol.commailto:natureXchange@aol.comshapeimage_4_link_0shapeimage_4_link_1shapeimage_4_link_2shapeimage_4_link_3shapeimage_4_link_4shapeimage_4_link_5shapeimage_4_link_6

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