Elevation In Tongue-flicking Rate Research Articles

Post-bite Elevation in Tongue-flick Rate by Neonatal Garter Snakes (Thamnophis radix)

A post-biting elevation in tongue-flicking rate was demonstrated experimentally in neonatal, ingestively naive garter snakes (Thamnophis radix). That the snakes also exhibited apparent searching movements suggests that strike-induced chemosensory searching occurs in nonvenomous snakes lacking previous experience with food or prey chemicals. Two litters of neonates differed in numbers of tongue-flicks emitted, but had similar relative magnitudes of response across experimental conditions. The existence of post-bite elevation in tongue-flick rate (and presumably strike-induced chemosensory searching) argues for a genetic basis for these chemosensory behaviors in a nonvenomous species of snake, extending the recent finding that strike-induced chemosensory searching is fully developed in ingestively naive neonatal rattlesnakes. Possible patterns of evolution of post-bite elevation in tongue-flick rate, and the strike-release-trail strategy of highly venomous snakes are discussed.

Do lingual behaviors and locomotion by two gekkotan lizards after experimental loss of bitten prey indicate chemosensory search?

Abstract Poststrike elevation in tongue-flicking rate (PETF) and strike-induced chemosensory searching (SICS) were assessed experimentally in two species of gekkonoid lizards belonging to families differing in foraging mode. PETF is an increase in rate of lingual protrusions after a prey item has been bitten and escapes or is removed from the mouth of a squamate reptile, whereas SICS is PETF combined with locomotory searching behavior. Eublepharis mucularius, the leopard gecko, is an actively, albeit slowly, foraging eublepharid. This species exhibited PETF for a duration of about five minutes based on total lingual protrusions. Labial-licks were initially much more frequent than tongue-flicks. A substantial increase in movement occurred during minutes 5-8, hinting that SICS might be present, but was not quite significant. SICS is likely present, as in other actively foraging lizards, but was not conclusively demonstrated. Handling the lizards induced increased locomotion in both the experimental condition and a control condition, presumably accounting for the apparent delay in onset of increased movement. The tokay gecko, Gekko gecko, a gekkonid ambush forager, performed no tongue-flicks, but exhibited PETF based on labial-licks during the first minute. SICS was absent. These findings support the hypothesis that SICS is absent in ambush foraging lizards, which do not use the lingual-vomeronasal system to search for prey. They are suggestive, but equivocal regarding the hypothesis that SICS is present in actively foraging lizards that exhibit lingually mediated prey chemical discrimination. The finding of PETF in G. gecko suggests that this species and several iguanians previously found to increase rates of labial-licking after biting prey may be able to detect prey chemicals.

Strike-Induced Chemosensory Searching in the Gila Monster

Strike-induced chemosensory searching (SICS), consisting of a poststrike elevation in tongue-flick rate (PETF) and searching movements following voluntary release or removal of prey from the predator's mouth, is experimentally verified in a helodermatid lizard, the gila monster (Heloderma suspectum). This finding agrees with previous results showing that PETF and SICS are present in all families of autarchoglossan lizards and snakes studied and in families of active foragers. Since SICS was found to last at least 10 min, longer than in any squamate reptiles except snakes and varanid lizards, the duration of SICS is greatest in the clade consisting of Varanoidea (Helodermatidae + Varanidae) and Serpentes. Long-lasting SICS in this clade is consistent with the hypothesis that morphological specialization of the tongue and vomeronasal system enhancing chemosensory detection and identification of prey may be important for the evolution of long duration. However, the short duration of SICS in teiids suggests the additional importance of phylogenetic constraints. Although the gila monster is venomous, SICS in this species has not led to evolution of a strikerelease-trail strategy as employed by highly venomous sankes, presumably because the gila monster does not eat large, dangerous prey and does not use its venom to subdue prey.

Strike-induced chemosensory searching by the anguid lizard Elgaria coerulea

AbstractStrike-induced chemosensory searching (SICS), including a post-strike elevation in tongue-flick rate (PETF) and searching movements following experimental removal of prey from the predator's mouth, is demonstrated to occur in an anguid lizard, Elgaria coerulea. This finding confirms predictions based on the previously established widespread occurrence of SICS in scleroglossan (especially autarchoglossan) lizard families and on a strong association between SICS and active foraging. Reasons why SICS should be favored by natural selection in active foragers are discussed, but the presence of SICS in anguids is attributed to phylogenetic inertia rather than adaptation. SICS was statistically significant only during the first two minutes in E. coerulea. Its limited duration in an anguid and much greater duration in helodermatids, varanids, and snakes suggest that prolonged SICS may have had a single origin in the common ancestor of Varanoidea or, much less likely, of (Varanoidea + Xenosauridae). Uncertainties about origins due to missing data on certain taxa and to unresolved phylogenetic relationships within Seleroglossa are discussed.

Prolonged poststrike elevation in tongue-flicking rate with rapid onset in gila monster,Heloderma suspectum: Relation to diet and foraging and implications for evolution of chemosensory searching

Experimental tests showed that poststrike elevation in tongue-flicking rate (PETF) and strike-induced chemosensory searching (SICS) in the gila monster last longer than reported for any other lizard. Based on analysis of numbers of tongue-flicks emitted in 5-min intervals, significant PETF was detected in all intervals up to and including minutes 41-45. Using 10-min intervals, PETF lasted though minutes 46-55. Two of eight individuals continued tongue-flicking throughout the 60 min after biting prey, whereas all individuals ceased tongue-flicking in a control condition after minute 35. The apparent presence of PETF lasting at least an hour in some individuals suggests that there may be important individual differences in duration of PETF. PETF and/or SICS are present in all families of autarchoglossan lizards studied except Cordylidae, the only family lacking linguallly mediated prey chemical discrimination. However, its duration is known to be greater than 2-min only in Helodermatidae and Varanidae, the living representatives of Varanoidea. That prolonged PETF and SICS are typical of snakes provides another character supporting a possible a varanoid ancestry for Serpentes. Analysis of 1-min intervals showed that PETF occurred in the first minute. A review of the literature suggests that a pause in tongue-flicking and delay of searching movements are absent in lizards and the few nonvenomous colubrid snakes tested. The delayed onset of SICS may be a specific adaptation of some viperid snakes to allow potentially dangerous prey to be rendered harmless by venom following voluntary release after envenomation and preceding further physical contact with the prey.

Strike-induced chemosensory searching is absent in the cordylid lizard,Cordylus cordylus, a scleroglossan ambush forager

Strike-induced chemosensory searching (SICS) was not detected experimentally in the cordylid lizard,Cordylus cordylus. Both components of SICS, a post-strike elevation in tongue-flick rate (PETF) and searching movements for attacked and released prey, were absent. The findings are consistent with previous data showing that PETF and/or SICS are lacking in all lizard families yet studied that forage primarily by ambush, but are present in actively foraging scleroglossan families and the herbivorous iguanian family Iguanidae. It is suggested that foraging behavior is a primary determinant of the presence or absence of SICS in lizards. Nevertheless, in most families in the two major clades, Iguania and Scleroglossa, the plesiomorphic foraging mode is retained. The findings agree with the prediction that SICS is absent in families lacking lingually mediated prey chemical discrimination (PCD), presumably due to selection against movement by ambush foragers that avoid being detected by either prey or predators because they remain motionless. Although PETF and SICS were absent, labial-licking and lingual movements similar to those observed after swallowing increased after biting prey, suggesting that the functions of these lingual movements may have been related to grooming. Locomotory movements did not increase following biting and appeared to represent avoidance of the experimenter.

Postbite elevation in tongue-flicking rate by an iguanian lizard,Dipsosaurus dorsalis

The herbivorous iguanid lizardDipsosaurus dorsalis exhibited PETF (postbite elevation in tongue-flicking rate), an increase in tongue-flicking rate after experimental removal from the mouth of food that had been bitten. This was demonstrated by a significantly higher tongue-flick rate after having bitten food than in three experimental conditions controlling for responses to the experimental setting, sight of food, and mechanical disturbance caused by the experimental removal of food from a lizard's mouth. As in most other families of lizards, PETF was brief, occurring only during the first minute. Lizards are divided into two major suprafamilial taxa, Iguania and Scleroglossa, consisting of carnivorous species characterized by two major foraging modes, ambush and active, and of herbivores and omnivores. PETF is absent in the two families of carnivorous iguanian lizards studied that are ambush foragers but present in three families of scleroglossan lizards that are active foragers. However, PETF is absent in the two species studied in a scleroglossan family, Gekkonidae, which forages by ambush, and present in an iguanian herbivore, as reported herein. We propose that the presence or absence of PETF, in addition to its phylogenetic determinants, is adaptively adjusted to foraging mode.

Strike-induced chemosensory searching by a teiid lizard, the golden tegu (Tupinambis nigropunctatus)

Strike-induced chemosensory searching (SICS) is experimentally demonstrated in a teiid lizard,Tupinambis nigropunctatus. SICS consists of a concurrent post-strike elevation in tongue-flick rate (PETF) and searching movements after voluntary release or escape of bitten prey or removal of prey from the predator's mouth. The results are consistent with previous data showing that PETF and/or SICS occur in all families of scleroglossan lizards and snakes and all families of actively foraging lizards yet studied. The relatively short duration of SICS (2 min) in a lizard having lingual and vomeronasal structure highly specialized for chemosensory sampling and analysis suggests that phylogenetic and ecological factors may be more important than morphology in determining the duration. The greatest known durations occur only in the presumably monophyletic clade containing varanoid lizards and snakes, all of which have highly developed chemical sampling and chemoreceptor apparatus, but in addition feed on prey that has a high probability of being relocated by prolonged scent-trailing. Because only active foragers move through the habitat while tongue-flicking and exhibit lingually mediated prey chemical discrimination, only active foragers may be expected to use SICS. SICS would appear to be useless to an ambush forager and might disrupt its defensive crypticity, rendering it more detectable to predators and prey. Therefore, it may be predicted that SICS is adaptively adjusted to foraging mode.

Prey chemical discrimination and strike-induced chemosensory searching in the lizardLiolaemus zapallarensis

Experimental tests were conducted to determine whether the ambush foraging iguanian lizard,Liolaemus zapallarensis, was capable of discriminating prey chemicals from control substances and whether this lizard exhibits strike-induced chemosensory searching (SICS) or its components after biting prey. The two components of SICS are a poststrike elevation in tongue-flicking rate (PETF) and apparent searching movements for relocation of prey that has been bitten, but released or escaped.Liolaemus zapallarensis failed to discriminate prey chemicals from control substances, but exhibited significant PETF lasting one minute. SICS was absent inL. zapallarensis because no post-strike movements were observed. The absence of both prey chemical discrimination and SICS exhibited byL. zapallarensis is common to all the insectivorous iguanians and ambush foraging lizards studied to date. However,L. zapallarensis is the first insectivorous iguanian species shown to exhibit PETF. The results suggest thatL. zapallarensis does not use the tongue for detection, identification, or relocation of prey while foraging. The possibility does remain thatL. zapallarensis may be capable of chemically identifying prey once the prey stimuli reach the oral cavity.

Elevation in tongue-flick rate after biting prey in the broad-headed skink,Eumeces laticeps

A postbite elevation in tongue-flicking (PETF) rate occurs in adult male broad-headed skinks,Eumeces laticeps. Males having bitten neonatal mice showed significantly higher tongue-flicking rates in the 2 min following experimental removal of the prey than did males in several control conditions. In a second experiment designed to separate the effects of tactile and chemical stimulation of the oral cavity during biting, males tongue-flicked at significantly higher rates in response to swabs bearing surface chemicals from neonatal mice than to identical swabs lacking the surface chemicals. These findings agree with previous data showing that PETF and searching movements occur in those families of lizards that can detect prey chemicals and use the tongue to do so during active foraging. The occurrence of PETF and putative searching movements supports the interpretation that PETF represents an attempt to relocate lost prey by chemosensory means. PETF was much briefer inE. laticeps than in many snakes and in a representative species from another lizard family and was not detectable after the first minute. This brevity is consistent with the prediction that PETF should be brief in squamates that feed on prey not likely to be located by scent-trailing.

Discrimination of integumentary prey chemicals and strike-induced chemosensory searching in the ball python,Python regius

Experimental tests show that the ball python (Python regius) has the ability to discriminate prey chemicals from control substances by tongue-flicking and exhibits a poststrike elevation in tongue-flicking rate (PETF). Prey chemical discrimination was revealed by significantly higher number of tongue-flicks and tongue-flick attack score in response to integumental chemicals from mice than to cologne or distilled water and by a higher frequency of biting in response to prey than control chemicals. PETF was indicated by higher tongue-flicking rates after biting than in several control conditions. Concurrent movements of the body suggest the operation of strike-induced chemosensory searching (SICS). Ecological factors affecting responses to prey chemicals, including defensive behaviors and characteristics of foraging behavior related to reliance on different sensory modalities, are discussed. The presence of PETF and SICS in a henophidian snake and in scleroglossan lizards suggests that these behaviors are plesiomorphic in snakes.

Responses to prey chemicals by a lacertid lizard,Podarcis muralis: Prey chemical discrimination and poststrike elevation in tongue-flick rate

The ability to discriminate prey chemicals from control substances and the presence of a poststrike elevation in tongue-flicking (PETF) rate are experimentally demonstrated in the lacertid lizard,Podarcis muralis, The tongue-flick attack score, a composite index of response strength, was significantly higher in response to integumental chemicals from cricket than to cologne or distilled water. The cricket chemicals additionally elicited a significantly greater rate of tongue-flicking and higher proportion of attacks by the lizards than did control stimuli. PETF combined with apparent searching movements strongly suggest the presence of strike-induced chemosensory searching (SICS). Experimental evidence indicates that both PETF and SICS occur in insectivorous representatives of three families of actively foraging autarchoglossan lizards, suggesting their widespread occurrence in such lizards. The adaptive roles of chemosensory behavior in the foraging behavior of P.Muralis are discussed. It is proposed that these lizards may form chemical search images and that PETF and SICS may have been present in the lacertilian ancestors of snakes.