Carnivorous Lizards Research Articles

Predator types, urbanization, and tree cover drive top-down control of herbivorous and carnivorous preys in an urban agroecosystem

ABSTRACT Prey-predator interactions hold significant importance, widely acknowledged as crucial processes within ecosystems. Yet, there is a scarcity of empirical data that effectively illustrates the influence of urbanization on such interactions. We performed a common garden experiment utilizing 1250 clay models to assess the predation risks faced by herbivorous and carnivorous prey in an urban agroecosystem in the southern Philippines. Our findings revealed significant differences in attack risks between the trophic levels, with herbivorous caterpillars (n = 246; 53.25%) experiencing higher predation rates compared to carnivorous lizards (n = 216; 46.75%). Interestingly, while the trophic level of the prey did not directly predict predation risk, the presence of predators showed significant effects. Arthropods emerged as the dominant predators of herbivorous prey compared to other predators, whereas mammalian predators predominantly attacked carnivorous prey. The landscape variable also had a strong influence on the risk of predation. We found that increasing tree cover was significantly related to increased predation risk, while built-up showed the opposite. Our research findings support the ‘increasing disturbance hypothesis’, suggesting that rising urbanization rates reduce predator diversity, resulting in a decrease and loss of predation pressure.

The anatomy, phylogenetic relationships, and autecology of the carnivorous lizard “Saniwa” feisti Stritzke, 1983 from the Eocene of Messel, Germany

The evolution and interrelationships of carnivorous squamates (mosasaurs, snakes, monitor lizards, Gila Monsters) are a contentious part of reptile systematics and go to the heart of conflict between morphological and molecular data in inferring evolutionary history. One of the best-preserved fossils in this motley grouping is “Saniwa” feisti Stritzke, 1983, represented by complete skeletons from the early-middle Eocene of Messel, Germany. We re-describe it on the basis of superficial examination, stereoradiography, and high-resolution X-ray computed tomography of new and published specimens. The scalation of the lizard is unique, consisting of small, keeled scales on the head (including a row of enlarged medial supraorbitals) and large, rhomboidal, keeled scales (invested by osteoderms) that covered the rest of the body. Two paired longitudinal rows of enlarged scales ran down the neck. The head was laterally compressed and box-shaped due to the presence of a strong canthal-temporal ridge; the limbs and tail were very long. Notable osteological features include: a toothed, strap-like vomer; septomaxilla with a long posterior process; palpebral with a long posterolateral process; a lacrimal boss and a single lacrimal foramen; a well-developed cultriform process of the parabasisphenoid; two hypoglossal (XII) foramina in addition to the vagus; a lack of resorption pits for replacement teeth; and possibly the presence of more than one wave of developing replacement teeth per locus. There are no osteological modifications suggestive of an intramandibular hinge, but postmortem displacement of the angular-prearticular-surangular complex in multiple specimens suggests that there might have been some degree of mobility in the lower jaw based on soft-tissue modifications. Using phylogenetic analyses on a data-set comprising 473 morphological characters and 46 DNA loci, we infer that a monophyletic Palaeovaranidae Georgalis, 2017, including Eosaniwa Haubold, 1977, lies on the stem of Varanidae Merrem, 1820, basal to various Cretaceous Mongolian taxa. We transfer feisti to the new genus Paranecrosaurus n. gen. Analysis of gut contents reveals only the second known specimen of the cryptozoic lizard Cryptolacerta hassiaca Müller, Hipsley, Head, Kardjilov, Hilger, Wuttke & Reisz, 2011, confirming a diet that was at least partly carnivorous; the preservation of the teeth of C. hassiaca suggests that the gastric physiology of Paranecrosaurus feisti (Stritzke, 1983) n. comb. had high acidity but low enzyme activity. Based on the foregoing and linear discriminant function analysis, we reconstruct P. feisti n. comb., as a powerful, widely roaming, faunivorous-carnivorous stem monitor lizard with a sensitive snout. If the molecular phylogeny of anguimorphs is correct, then many of the features shared by Helodermatidae Gray, 1837 and Varanidae must have arisen convergently, partly associated with diet. In that case, a reconciliation of morphological and molecular data would require the discovery of equally primitive fossils on the helodermatid stem.

Diet of Nile Monitors (Varanus niloticus) Removed from Palm Beach and Broward Counties, Florida, USA

Abstract Nile Monitors (Varanus niloticus) are large (up to 2.4 m in length), semiaquatic, carnivorous lizards native to Sub-Saharan Africa. Nile Monitors are reported from southeastern Florida nea...

Genetic variation across trophic levels: Atest of the correlation between population size and genetic diversity in sympatric desert lizards.

Understanding the causes of genetic variation in real populations has been elusive. Competing theories claim that neutral vs. selective processes have a greater influence on the genetic variation within a population. A key difference among theories is the relationship between population size and genetic diversity. Our study tests this empirically by sampling two species of herbivorous lizards (Dipsosaurus dorsalis and Sauromalus ater) and two species of carnivorous lizards (Crotaphytus bicinctores and Gambelia wislizenii) that vary in population size at the same locality, and comparing metrics of genetic diversity. Contrary to neutral expectations, results from four independent loci showed levels of diversity were usually higher for species with smaller population sizes. This suggests that selective processes may be having an important impact on intraspecific diversity in this reptile community, although tests showed little evidence for selection on the loci sequenced for this study. It is also possible that idiosyncratic histories of the focal species may be overriding predictions from simple neutral models. If future studies show that lack of correlation between population size and genetic diversity is common, methods using genetic diversity to estimate population parameters like population size or time to common ancestor should be used with caution, as these estimates are based on neutral theory predictions.

Nutritional fibrous osteodystrophy with chondroid metaplasia in a Nile monitor, Varanus niloticus

Carnivorous reptiles are not usually thought of as being prone to metabolic bone disorders. A constant diet lacking in calcium or bone and/or high in phosphorus or low in vitamin...

Locomotion, Energetics, Performance, and Behavior: A Mammalian Perspective on Lizards, and Vice Versa.

Animals are constrained by their abilities and by interactions with environmental factors, such as low ambient temperatures. These constraints range from physical impossibilities to energetic inefficiencies, and may entail trade-offs. Some of the constraints related to locomotion and activity metabolism can be illustrated through allometric comparisons of mammals and lizards, as representative terrestrial vertebrate endotherms and ectotherms, respectively, because these lineages differ greatly in aerobic metabolic capacities, resting energetic costs, and thermoregulatory patterns. Allometric comparisons are both useful and unavoidable, but "outlier" species (unusual for their clade) can also inform evolutionary scenarios, as they help indicate extremes of possible adaptation within mammalian and saurian levels of organization. We compared mammals and lizards for standard metabolic rate (SMR), maximal oxygen consumption during forced exercise (VO2max), net (incremental) cost of transport (NCT), maximal aerobic speed (MAS), daily movement distance (DMD), daily energy expenditure (DEE) during the active season, and the ecological cost of transport (ECT = percentage of DEE attributable to locomotion). (Snakes were excluded because their limbless locomotion has no counterpart in terrestrial mammals.) We only considered lizard SMR, VO2max, NCT, MAS, and sprint speed data if measured at 35-40 °C. On average, MAS is ∼7.4-fold higher in mammals, whereas SMR and VO2max are ∼6-fold greater, but values for all three of these traits overlap (or almost overlap) between mammals and lizards, a fact that has not previously been appreciated. Previous studies show that sprint speeds are similar for smaller mammals and lizards, but at larger sizes lizards are not as fast as some mammals. Mammals move ∼6-fold further each day than lizards, and DMD is by far the most variable trait considered here, but their NCT is similar. Mammals exceed lizards by ∼11.4-fold for DEE. On average for both lineages, the ECT is surprisingly low, somewhat higher for lizards, and positively allometric. If a lizard and mammal of 100 g body mass were both to move their entire DMD at their MAS, they could do so in ∼21 and 17 min, respectively, thus de-emphasizing the possible importance of time constraints. We conclude that ecological-energetic constraints related to locomotion are relatively more likely to occur in large, carnivorous lizards. Overall, our comparisons support the idea that the (gradual) evolution of mammalian endothermy did not necessarily require major changes in locomotor energetics, performance, or associated behaviors. Instead, we speculate that the evolution of thermoregulatory responses to low temperatures (e.g., shivering) may have been a key and "difficult" step in this transition.

First Evidence for Reproduction of Nile Monitors (Varanus niloticus) in Palm Beach County

Varanus niloticus (Nile Monitor) is a large, carnivorous lizard native to sub-Saharan Africa. A breeding population of Nile Monitors was documented in southwestern Florida (Lee County) in 2004. In 2011, the Florida Fish and Wildlife Conservation Commission began surveying the C-51 canal on the southeastern Florida coast in Palm Beach County in response to multiple reports of monitor lizards. These surveys resulted in observations of 9 Nile Monitors, including a hatchling and copulating pair. Three additional hatchlings were later reported by private citizens. These observations provide evidence of a breeding population of these non-native lizards in southeastern Florida.

How to train your Komodo dragon

What do you do when a giant carnivorous lizard starts heading straight for you? Try giving it a good scratch behind the ears

Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record

Abstract We assembled a dataset of 192 carefully selected species—51 extinct and 141 extant—and 976 apomorphies distributed among 610 phenotypic characters to investigate the phylogeny of Squamata (“lizards,” including snakes and amphisbaenians). These data enabled us to infer a tree much like those derived from previous morphological analyses, but with better support for some key clades. There are also several novel elements, some of which pose striking departures from traditional ideas about lizard evolution (e.g., that mosasaurs and polyglyphanodontians are on the scleroglossan stem, rather than parts of the crown, and related to varanoids and teiids, respectively). Long-bodied, limb-reduced, “snake-like” fossorial lizards—most notably dibamids, amphisbaenians and snakes—have been and continue to be the chief source of character conflict in squamate morphological phylogenetics. Carnivorous lizards (especially snakes, mosasaurs and varanoids) have proven a close second. Genetic data, presumably less bur...

Folk Knowledge and Distribution of the Komodo Dragon (Varanus komodoensis) on Flores Island

The world's largest lizard, the Komodo dragon, occurs not only on its namesake island but also on the far larger eastern Indonesian island of Flores. Since it first became known to western science in the early 20th century, local people have provided information on the species, its ecology, and distribution on Flores. While the lizard's occurrence in westernmost Flores has been known since its discovery by Europeans, this paper reviews recent ethnographic evidence for the continuing presence of Komodo dragons in more easterly parts of north coastal Flores where its occurrence has yet to be verified zoologically or has been documented only recently. Also discussed are the carnivorous lizard's relationship with humans and domestic animals in north central Flores, its place in local symbolism, and different names applied in various parts of the Flores region to the Komodo dragon and another, smaller and sometimes sympatric Varanid, the water monitor.

Size evolution in island lizards

ABSTRACTAim The island rule, small animal gigantism and large animal dwarfism on islands, is a topic of much recent debate. While size evolution of insular lizards has been widely studied, whether or not they follow the island rule has never been investigated. I examined whether lizards show patterns consistent with the island rule.Location Islands worldwide.Methods I used literature data on the sizes of island–mainland population pairs in 59 species of lizards, spanning the entire size range of the group, and tested whether small insular lizards are larger than their mainland conspecifics and large insular lizards are smaller. I examined the influence of island area, island isolation, and dietary preferences on lizard size evolution.Results Using mean snout–vent length as an index of body size, I found that small lizards on islands become smaller than their mainland conspecifics, while large ones become larger still, opposite to predictions of the island rule. This was especially strong in carnivorous lizards; omnivorous and herbivorous species showed a pattern consistent with the island rule but this result was not statistically significant. No trends consistent with the island rule were found when maximum snout–vent length was used. Island area had, at best, a weak effect on body size. Using maximum snout–vent length as an index of body size resulted in most lizard populations appearing to be dwarfed on islands, but no such pattern was revealed when mean snout–vent length was used as a size index.Main conclusions I suggest that lizard body size is mostly influenced by resource availability, with large size allowing some lizard populations to exploit resources that are unavailable on the mainland. Lizards do not follow the island rule. Maximum snout–vent length may be biased by sampling effort, which should be taken into account when one uses this size index.

Correlations between lizard cranial shape and diet: a quantitative, phylogenetically informed analysis

Although the relationship between dietary and phenotypic specialization has been well documented for many vertebrate groups, it has been stated that few such general trends can be established for lizards. This is often thought to be due to the lack of dietary specialization in many lizards. For example, many species that are reported to be insectivorous may also consume a variety of plant materials, and the reverse is often true as well. In this study, we investigate whether a correlation exists between general cranial form and dietary niche in lizards. Additionally, we test previously proposed hypotheses suggesting that herbivorous lizards should be larger bodied than lizards with other diets. Our data indicate that lizards specializing in food items imposing different mechanical demands on the feeding system show clear patterns of morphological specialization in their cranial morphology. True herbivores (diet of fibrous and tough foliage) are clearly distinguished from omnivorous and carnivorous lizards by having taller skulls and shorter snouts, likely related to the need for high bite forces. This allows herbivores to mechanically reduce relatively less digestible foliage. Carnivores have relatively longer snouts and retroarticular processes, which may result in more efficient capture and processing of elusive prey. When analysed in an explicit phylogenetic context, only snout length and skull mass remained significantly different between dietary groups. The small number of differences in the phylogenetic analyses is likely the result of shared evolutionary history and the relative paucity of independent origins of herbivory and omnivory in our sample. Analyses of the relationship between diet and body size show that on average herbivores have a larger body size than carnivores, with omnivores intermediate between the two other dietary groups.

Distribution, extent, and evolution of plant consumption by lizards

AbstractAnimal diets crucially affect fitness, yet many aspects of their ultimate determinants are unknown. The distribution and extent of herbivory in lizards, its evolutionary history, and ecological factors that may favour it are discussed. Most lizards are exclusively or primarily carnivorous, yet many species eat some plants and a few are almost exclusively herbivorous. Based on a literature survey of diets of over 450 lizard species, the distribution and degree of omnivory and herbivory are described. Some plants occur in the diets of slightly over half of lizard species, and plants formed 10% or more of the dietary volume of 12.1% of species, and 90% or more of the diet of 0.8% of species. The greatest percentage of omnivorous species (> 10% plant diet), over 30% in each, and highest mean percentage plant matter in the diet are in Iguanidae, Corytophanidae, Gerrhosauridae, Agamidae, Xantusiidae, and Tropiduridae. Numerous other omnivores occur in Lacertidae and Scincidae and fewer in several additional families. Herbivorous lizards (> 90% plant volume) tend to be folivorous and to possess adaptations for processing leaves, including specialized dentition for cutting or reducing leaves, elongated intestines, colic valves that slow passage of food, and intestinal flora that digest cellulose. Omnivorous lizards lacking such specializations may eat some leaves, but consume much more fruit, flowers, and seeds, plant parts that are easy to digest, likely to be very abundant seasonally, and may be highly nutritious. Some lizards eat nectar and pollen; even sap is eaten by at least one gecko. Ontogenetic increase in plant consumption and decrease in prey consumption is known, but its generality has been controversial. Such ontogeny has been demonstrated in three iguanid species, a skink, a lacertid, two tropidurids, a phrynosomatid, and two corytophanids, but it does not occur in some other species. The importance of specific foods may vary with age. Omnivory and/or herbivory have originated in many lizard families, with at least nine origins in Iguania and 23 in Scleroglossa. Origins have been rare in Gekkonoidea and Anguimorpha and common in Scincomorpha, especially in Lacertidae and Scincidae. Losses of omnivory have been much less frequent than gains. Only a few origins can account for all the herbivory in lizards. Concentrated changes tests show that there is a significant association in Lacertidae, Lacertiformes, Lacertoidea, Scincidae, and Scleroglossa between insularity and omnivory. Insular lizards may broaden their diets to compensate for limited availability of prey. Addition of other factors that reduce availability of prey, i.e. extreme aridity and cave‐dwelling, to insularity, strengthened the relationship to omnivory in Lacertidae and Lacertoidea. We were unable to demonstrate a role of aridity independent of insularity, but present anecdotal evidence suggests that it may promote evolution of plant consumption. Large body size in lizards has long been associated with herbivory, and more recently, with omnivory in lacertid lizards. Using a conventional regression approach in which each species is considered to supply an independent data point, this relationship was confirmed for all lizards. Although larger species have diets with more plants, plant consumption accounts for only 9% of the variation in body length, which is not surprising given that other factors such as predation, competition, and sexual selection affect body size. The frequency of transitions body size associated with transitions to omnivory or carnivory was also examined. In Iguania, Scleroglossa, and all lizards, transitions supporting the hypothesis that omnivory favours increase in body size were significantly more frequent than non‐supporting transitions. This suggests that substantial plant consumption favours evolution of larger size, probably because of the energetic considerations first presented by Pough (1973). Because actively foraging lizards move widely through the habitat to locate prey and tongue‐flick to locate prey by chemical cues, we hypothesized that they may be more likely to evolve omnivory than ambush foragers, which wait motionless for prey and do not tongue‐flick to locate or identify prey. The basis of this prediction is that the wider seaching of active foragers predisposes them to contact with a greater variety and quantity of plants and that chemosensory tongue‐flicking used by omnivores to identify plant food might be easier to evolve in active foragers that already use pre‐chemical discrimination. The prediction is supported by a significantly greater per species frequency of origins of omnivory by active foragers than by ambushers. A scenario for the progressive evolution of omnivory and herbivory from ancestrally carnivorous lizards is discussed.

Absence of Discriminatory Tongue-Flicking Responses to Plant Chemicals by Helodermatid Lizards

criminate between palatable plant food and control stimuli by tongue-flicking (Cooper and Alberts, 1990; Cooper, 2000a, 2000b, 2000c; Cooper and Flowers, 2000). Because tongueflicking serves to sample chemicals from environmental substrates for delivery to the vomeronasal organs, and because prey chemical discrimination in lizards requires vomerolfaction (Cooper and Alberts, 1991), plant chemical discriminations presumably are vomerolfactory. In snakes there is a close correspondence between diet and strength of chemosensory responses to potential foods (Burghardt, 1970; Arnold, 1981; Cooper et al., 2000a), but no such correspondence has been established in lizards. Because the large majority of lizards consume little or no plant matter (Iverson, 1982), herbivory may afford an opportunity to examine a similar correspondence between diet and chemosensory responsiveness in lizards. To assess whether such correspondence occurs, WEC has undertaken comparative studies to assess responses by herbivorous and omnivorous lizards to plant chemicals and prey chemicals. Responses to plant chemicals by species that do not eat plants must be determined to learn whether plant chemical discriminations are acquired in association with plant consumption. Actively foraging insectivorous and carnivorous lizards respond to chemical cues from animal prey by tongue-flicking and biting the stimulus sources, discriminating between them and control substances (Cooper, 1995, 1997, 1999). The ability to identify prey using chemical cues may be adaptive for location and recognition of prey (Cooper, 1994). If the ability to recognize prey is specific, actively foraging carnivores should not respond strongly to chemical cues from plants palatable to herbivorous lizar s. This prediction has been substantiated for scincine (Cooper et al., 2000b) and lygosomine skinks (Cooper and Hartdegen, 1999), a lacertid and a teiid (Cooper et al., 2000c); a eublepharid gecko (Cooper and Habegger, 2000), and a varanid (Cooper and Habegger, in press). For a phylogenetically based examination of correlated evolution between herbivory and plant chemical discrimination, information is needed on responses to plant chemicals for a wide taxonomic range of herbivores and insectivores. In this study we present data showing no indication of strong response to plant chemicals by the 2 extant helodermatid lizards, the gila monster, Heloderma suspectum, and the Mexican beaded lizard, H. horridum. The gila monster discriminates prey chemicals from control substances by tongue-flicking (Cooper, 1989) and exhibits prolonged strike-induced chemosensory searching, an increase in tongue-flick rate and scent-trailing to locate lost prey (Cooper et al., 1994; Cooper and Arnett, 1995; Garrett et al., 1996). Chemosensory behavior has not been studied in Mexican

Diet of a large carnivorous lizard, Varanus varius

The diet of a population of lace monitors, Varanus varius, at Lake Burrendong was examined over the spring, summer and autumn seasons. Carrion dominated the diet; it was eaten consistently in all seasons by all the monitors and was generally supplemented by live mammalian kills and invertebrates. Nestling birds and rabbits as well as bird and reptile eggs were eaten mainly during the flush periods of the spring and early summer. The data reported here agree with other reports for the genus Varanus: that they are generalist carnivorous predators and scavengers.

Specific Dynamic Action of a Large Carnivorous Lizard, Varanus albigularis

Varanus albigularis inhabits grasslands of southern and eastern Africa and experiences months of fasting during the dry season (May–December) followed by voracious feeding during the wet season (January–April). Previous studies have found that sit-and-wait foraging snakes, which also experience long intervals between large meals, exhibit unprecedented increases in post-feeding metabolism, which reflects the added cost of up-regulating a previously quiescent gut and digesting a large meal. Hence we measured pre- and post-prandial oxygen consumption rates (V̇O 2) of adult V. albigularis in order to observe whether they exhibit similarly large metabolic responses to digestion as sit-and-wait foraging snakes. Following the consumption of meals consisting of ground turkey and snails, hard-boiled eggs, or juvenile rats, lizards rapidly increased their V̇O 2 to peak within 24–27 hr at 7–10 times pre-feeding values (mean = 0.035 mL O 2 · g −1 · h −1). During the 60–90 hr of significantly elevated V̇O 2, the extra oxygen consumed (the specific dynamic action) represented an energy expenditure of 830–1260 kJ. For meals that were fully digested, specific dynamic action equalled 24% of ingested energy. The magnitudes of V. albigularis post-prandial metabolic responses are similar to those previously observed for sit-and-wait foraging snakes. Like sit-and-wait foraging snakes, V. albigularis may also down-regulate intestinal performance during their months of fasting (suggested by their relatively low standard metabolic rate) and then up-regulate their gut (bearing its high energetic cost) upon feeding.

Water and Energy Use in a Free-Living Tropical, Carnivorous Lizard, Tupinambis teguixin

There is a reasonable amount of published information on the water and energy requirements of reptiles from arid/semiarid and temperate environments (see reviews by Nagy, 1982a, 1982b; Nagy and Peterson, 1988); however there is a dearth of such information from tropical/equatorial habitats. Much of the tropics is characterized by comparatively uniform daily ambient temperatures, whereas the pattern of rainfall is quite seasonal being confined predominantly to a wet season of some five months or so. Out-

Sensory cues and foraging decisions in a large carnivorous lizard, Varanus albigularis

The white-throated savanna monitor, Varanus albigularis, is a large (>5 kg) carnivorous lizard that inhabits the arid savanna in southern Africa. In the natural environment, feeding occurs only during the 4-month wet season when invertebrate and small vertebrate prey are abundant. Seven experiments were conducted to examine the foraging, feeding and sensory discrimination behaviour of these lizards towards land snails, a favoured natural prey. Subjects were 16 subadult, captive-hatched lizards. Each lizard received several trials in choice discrimination tests with two or three types of snail stimuli differing in visual, chemical or tactile cues. Lizards differentiated between land snails using both visual and chemical cues. Large snails and those requiring short handling times were chosen over small snails and those requiring greater handling time. Neither snail movement nor snail weight were significant cues in choice of individual prey. Lizards preferred empty shells with fresh snail odour to empty snail shells without odour. The results suggest that these monitor lizards discriminate between prey items using visual and chemical cues. A result of their selectivity is obtaining a high caloric reward at a minimum energetic cost.

Prey Chemical Discrimination and Foraging Mode in Gekkonoid Lizards

Relationships among phylogeny, foraging mode, and prey chemical discrimination by tongue-flicking were investigated by experimentally testing for the presence of lingually mediated prey chemical discrimination in representatives of two families of gekkonoid lizards having different foraging modes. In the experiments, the tongue-flicking and biting responses of each lizard were recorded in response to cotton swabs bearing three classes of stimuli: prey surface chemicals, cologne as a pungency control, and deionized water as an odorless control. In a eublepharid species, Eublepharis macularius, the tongue-flick rate, the proportion of individuals attacking the swab, and a composite measure combining effects of tongue-flicking and attack (TFAS(R)) were significantly higher and the latency to attack significantly shorter in the prey stimulus condition than in the other conditions, which did not themselves differ. In contrast, no tongue-flicking or attacks were observed in any of the conditions for two gekkonid species, Thecadactylus rapicauda and Gekko gecko. Because eublepharids are active foragers whereas gekkonids are ambush foragers, prey chemical discrimination was associated with active foraging, as predicted. Prior to this report, all families of ambush-foraging lizards known to lack prey chemical discrimination belonged to a single clade, Iguania. Actively foraging carnivorous lizards identify prey by chemical cues and belong to Scleroglossa, which includes the families studied here. It is argued that adoption of active foraging may have induced selection for gain of prey chemical discrimination involving tongueflicking in eublepharids. Phylogeny and the presence or absence of prey chemical discrimination are closely related in lizard families because foraging mode is conservative in the major clades Iguania and Scleroglossa.

Multiple functions of extraoral lingual behaviour in iguanian lizards: prey capture, grooming and swallowing, but not prey detection

Abstract. Lingual chemosensory sampling allows many lizards to detect and later relocate prey after failed capture attempts. Although several families in the iguanian radiation do not discriminate prey chemicals prior to attack on prey, little is known about their responses to oral contact with prey chemicals during successful or failed predation attempts. Experimental tests of responses to swabs bearing surface chemicals from prey revealed no evidence of prey chemical discrimination in two species from different iguanian families. Neither of these nor a third species exhibited strike-induced chemosensory searching in experiments that readily elicit this behaviour in many other lizard taxa. None of the three species performed searching movements after ingesting prey. The form of lingual protrusion observed differed from that used by other lizards to detect prey. Instead of being directed to environmental substrates, the tongue was used to capture prey or lick the labial scales, or was protruded in a manner suggesting postural adjustments or cleaning subsequent to swallowing. Comparison of present and previous results suggests that use of lingually mediated prey chemical discrimination prior to attack and strike-induced chemosensory searching after attack may be coupled in carnivorous lizards, both being present or both absent. Available data suggest that lingual sampling to detect prey in pre- and post-attack settings occurs in actively foraging lizards, but not in ambush foragers, and that it typically occurs in both settings in scleroglossans, but not iguanians. Although iguanians do not use the tongue to detect prey chemicals before attack, lingual prehension of prey or labial-licking may have provided the contact with chemicals on environmental substrates that led to selection for tongue-flicking to detect prey chemicals or pheromones.