Anita. Behav., 1983, 31, 718-723 CONTEXT-CORRELATED PARAMETERS OF SNAKE AND LIZARD TONGUE-FLICKING BY DORIS GOVE & GORDON M. BURGHARDT Departments of Zoology and Psychology, University of Tennessee, Knoxville, Tennessee 37996 Abstract. Three parameters of tongue-flicking in snakes and lizards (oscillation duration, oscillation number and relative circumscribed area) were examined in filmed captive contexts. A comparative survey of four lizard and 10 snake species uncovered a consistent trend for exploratory tongue flicks to have both shorter oscillation durations and smaller relative circumscribed areas than defensive tongue flicks. Young sibling garter snakes (Thamnophis sirtalis) studied in four contexts (feeding, exploration, social, defence) replicated the above results and clearly distinguished the other two contexts as well. Fine-grained studies of tongue movement topography have methodological and evolutionary impli- cations for the study of squamate reptile behaviour. Chemoreceptive tongue-flicking is common in the lizards and snakes (Squamata, Reptilia). Tile tongue protrudes from the mouth, picks up air- borne or substrate particles and delivers them to the vomeronasal organ (Jacobson's organ) on the roof of the mouth (Broman 1920; l<.ahmann 1932; Wilde 1938; Burghardt 1980; Halpern & Kubie 1980; Gillingham & Clark 1981). Most studies of tongue-flicking have involved counting the numbers of protrusions in experimental situations and assuming that higher numbers of flicks were positively correlated with the rele- evance of the stimulus eliciting the flicks (e.g. Wilde 1938; Burghardt 1966, 1970; Kubie 1977; Kubie & I-Ialpern 1978; Bissinger & Simon 1979). Ulinski (1972) analysed the oscillations of tongue-flicking in the boa (Boa constrictor), and discovered that oscillation durations were fairly constant. In an earlier paper, Gore (1979) described a method for the comparative study of the topo- graphy of snake and lizard tongue-flicking, and hypothesized how the behaviour evolved, from the simple downward extensions of lizards which collect food, water and limited chemical informa- tion, to the complex multiple oscillations of snakes. Tongue-flicking data were presented for 25 lizard species in 10 families and 30 snake species in five families. Three types of tongue- flicks were seen: (1) the simple downward exten- sion, performed by all subjects, in which the tongue usually touches the substrate or some object; (2) the single oscillation, performed by the more advanced lizards and all of the snakes, which involves first an upward then a downward swing of the tongue, with or without contact; and (3) the multiple-oscillation tongue-flick, performed by snakes and three lizard species, which involves several oscillations each time the tongue emerges from the mouth. A specialized tongue-flick was seen in three families of ad- vanced snakes (Colubridae, Elapidae, and Crotalidae), which involves slow oscillations and long extensions. These appear when the snakes are disturbed or threatened, and seem to serve as ritualized warning displays. in this paper, we describe how tongue- flicking varies according to the context of the behaviour. Some work has been done in this area. Svoboda (1969) described 'long' and 'short' tongue-flicks of the lizard Lacerta agilis, and determined which was more likely to occur in various contexts. Kubie (1977) and Halpern & Kubie (1983) reported that garter snakes (Thamnophis sirtalis) gave many short-extension tongue-flicks while following a food trail, but gave long-duration long-extension tongue-flicks during open-field testing. Here we bypass simple frequency or overall duration measures, and utilize parameters of tongue extension such as oscillation number, oscillation duration, and relative circumscribed area sampled. First we present a general survey of tongue flicking by selected lizard and snake species in exploratory and defensive contexts, then a more detailed study of one species (Thamnophis sirtalis) in four contexts. Methods Subjects Four species of lizards, two species of primi- tive snakes (boas), and eight species of advanced snakes (colubrids), were filmed in two contexts: exploring and defensive (see Table I). The lizard species chosen were from those families showing 718