University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Faculty Publications and Other Works -- Ecology and Evolutionary Biology Ecology and Evolutionary Biology January 1978 Ethological Considerations in the Experimental Study of Lizard Behavior Neil Greenberg University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_ecolpubs Part of the Behavioral Neurobiology Commons, Medical Sciences Commons, and the Psychology Commons Recommended Citation Greenberg, Neil, "Ethological Considerations in the Experimental Study of Lizard Behavior" (1978). Faculty Publications and Other Works -- Ecology and Evolutionary Biology. https://trace.tennessee.edu/utk_ecolpubs/17 This is brought to you for free and open access by the Ecology and Evolutionary Biology at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Faculty Publications and Other Works -- Ecology and Evolutionary Biology by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. BeMwitw <m4 Neaf'Olotnl of Li.lotU N. G.....,nberg and P. D. lber-n, eda. NDI:H, 1978. Ethological Considerations in the Experimental Study of Lizard Behavior NeU Greenberg* Laboratory of Brain Evolution and Behavior National Institute of Mental Health SUMMARY. The importance of an ethological approach to the experimental study of an un­ familiar species is described and several of its problems discussed. The selection of units of be.. havior is a crucial first step in the development of a behavior inventory. The correlation of a behavioral unit with a particular context is necessary to ascribe function to that unit and to de� velop an etbogram. Me thods of studying lizards under controlled conditions are described and discussed. Constraints on behavior that must be considered in an experimental study include the microclimate and its thermal qualities, food and water, shelter utilization, and social behavior. Ritualized display patterns are proposed as sources of hypotheses about the neurophysiological control of social communications. INTRODUCTION The importance of the ethogram in the interpretation of an experimental study of This report will first discuss some issues a species is stressed by most ethologists (e.g., in an ethological approach to the study of an Lorenz, 1935, trans. 1970 :111; Tinbergen, unfamiliar species and will then describe 1951; Thorpe, 1973). Failure to consider all some observations that bear on the. develop­ aspects of normal behavior has diminished ment of an experimental design for the study the usefulness of many experimental studies of lizard behavior in the laboratory. (Adams, 1973; Eibl�Eibesfeldt, 1970; The observations described, both my own Thorpe, 1973). and those gleaned from the literature, are presented to indicate the complexity of the environmental constraints on lizard behavior. Units of Behavior They constitute something of a guide for re­ searchers-be they students of reptiles de­ .A problem in developing ethograms has voted to a favorite group or those who see proven to be the objective delineation of lizards as a possible model for experimentally separate units in what is a continuum · of testing hypotheses about the causation and behavioral patterns. To minimize the arbi­ function of behavior. trary nature of behavioral classification, the investigator attempts to identify reliable, THE ETHOGRAM AND UNITS easily recognizable diagnostic features. OF BEHAVIOR Ideally, behavioral units should be of the Naturalistic observation is the essence of type that a neurophysiologist could deal with. ethology and the fountainhead of hypotheses Barlow (1968) asserts that, in this regard, about the causation and function of behavior only quantifiable behavior is of interest be­ as well as the foundation on which experi­ cause the behavior must be mathematically mental tests of these hypotheses must be modeled if it is to beo c nsidered in neuro­ built. physiological terms. But preoccupation with quantification can be hazardous, .interfering •Present address: Department of Zoology, Univer­ sity of Tennessee, Knoxville, TN 87916. with the Gestalt perception of a phenomenon 203 204 Greenberg that is crucial to generating creative hy­ been treated as a single unit, when they may, potheses (Lorenz, 1971). For example, time in fact, represent multiple behavioral pat­ sampling can often be misleading unless the terns which have coalesced; neck and limb environmental or social context is considered, movements may represent two alternative and that is not always possible (Driver, mechanisms which have become combined to 1968). As Vowles (1975) points out, a pre­ effect a display. Some species have several occupation with quantification may be an bobbing movements for different displays understandable response to the subjective which utilize limb and neck movement to and introspective approach of early different degrees or even dispense with one psychology. type of movement. Another difficulty in of be­ The selection of units of behavior must be defining units havior is that motor patterns and sequences suitable to the questions being asked. The are too easily defined in functional hard decisions of "lumping" and "splitting," terms which combine explanation and description. familiar to taxonomists, must also be made This can interfere with comparative when behavior patterns are to be organized inter­ pretations and replications of the into manageable groups. This is true at the original study. level of individual units in a coordinated sequence as well as in more complex be­ havioral categories. It is often helpful to The Evolutionary Perspective begin with a broad overview of general ac­ tivity patterns and then subdivide them until One goal of comparative studies is the de­ the appropriate "resolution" is achieved velopment of the evolutionary perspective (Fig. 1). A neurophysiologist may profitably that leads to an appreciation of the genetic deal with units as tine as a muscle group and (and to that extent "innate") contribution to its associated actions (e.g., the "functional behavior (Brown, 1969). Comparative stud­ unit" of Liem, 1967, cited by Barlow, 1968: ies are also useful to investigators in sug­ 217), while a population biologist may be gesting hypotheses and in analyzing the concerned with a complete communicative adaptive aspects of natural units of behavior. act and its consequences. Both analogy and homology are important While too fine a preliminary analysis can considerations in thinking comparatively obscure a behavioral pattern with trivial de­ about behavior. tails, if the units of behavior utilized in the In evolutionary biology, Mayr (1969) study of a species are too broad, difficulties asserts that only homologous characters are may emerge that could not have been antici­ of taxonomic importance. Homology origi­ pated until the comparative perspective was nally referred to an anatomical correspon­ brought to bear on a problem. For example, dence between structures in two animals details of behavior that might suggest a sharing a similar body plan, but, in current physiological mechanism or the evolutionary use, the evolutionary explanation for hom­ sources of signal behavior can be overlooked. ology has usurped the original meaning of 1974). This . can be a problem in studies of display the term (Beer, behavior where the individual components Two characters under consideration by a of the display and/or their time course are biologist may differ markedly in form or often not as clearly delineated as the general function and yet be related through deriva­ form of the display. A notable exception is tion from a common ancestral precursor. the comparative study of the vertical 41bob- Such relatedness may provide valuable in­ . bing" movements of displaying males of the sights into the causation of dissimilar be­ genus Sceloporu8 by Purdue and Carpenter havioral patterns and the manner in which (1972). Such analysis is useful because the animals evolve. body movements in the ubiquitous bobbing The idea of behavioral homology, however, displays of iguanid lizards have generally is a continuing source of confusion. The con- FORAGING STAlKING \"\ walking (walk·ing) ' . l anerttve body-lean display � and pause head tipped * down. lunge - 1'7·head r � .....t"'4 head tippecl � PERCHING • a anterior food-nudge head exposed negative I t;l:J body up perpendicular COVERT BEHAVIOR • low-mod fully emerged orientation [ fadlitated tl� at threshold { oblique stance � sleeping and ______ .,._ covert activity lateral expansion and (cotd 'SLibstrilte) body-up low-mod u }� (or warm substrate) svbs.trate FEEDING J warm" body-down ventral adpression head·down [ + . rtree•ing··· food-grab postenor adpressoon J food-shake RETREAT �::�:,::;r:a� } t pe j,.L.. '------------------thennalretreat �-----------£------------------------------�------� '---------------------- feeding retreat chew ------------------------ nocturnal retreat ••d swallow Figure 1. A preliminary ethogram of the blue spiny lizard, SceloportUJ cy£�nogentfs. Such a broad overview of daily.ma intenance patterns may be used as � baseline against which subsequent manipulations may be contrasted to indicate distortions in behavior induced by experimental or maintenance � reg1mens. � 206 Greenberg cept resists attempts at rigorous definition heuristic value of such considerations, how­ and yet is of obvious use. Atz