Tongue Flicking Research Articles

Absence of prey-chemical preferences in newborn rattlesnakes ( Crotalus cerastes, C. enyo, and C. viridis)

Cotton swabs soaked in water or in extracts of surface substances from two prey organisms (lizard, mouse) and five nonprey organisms (cricket, garter snake, fish, salamander, worm) were presented for 60 sec to 17 ingestively naive neonatal rattlesnakes (six Crotalus cerastes, five C. enyo, and six C. viridis). No rattlesnake struck any cotton swab. Mean tongue flick rate was not significantly greater when prey odors were presented than when control swabs or nonprey odors were presented. Additional tests were conducted with small skin patches from two prey and two nonprey organisms (lizard, mouse, cricket, fish). Six C. cerastes did not strike any of these items, and the mean rates of tongue flicking emitted to the four skin patches did not differ significantly.

Rate of tongue flicking by garter snakes ( Thamnophis radix haydeni) and Rattlesnakes ( Crotalus v. viridis, Sistrurus catenatus tergeminus, and Sistrurus catenatus edwardsi) during prolonged exposure to food odors

Garter snakes (Thamnophis radix haydeni) emitted more tongue flicks in environments containing fish or salamander odors than in a control environment. This indicates that appetitive searching (guided by the vomero-nasal system) can be activated by olfactory cues. Specimens of three taxa of rattlesnakes (Crotalus viridis viridis, Sistrurus catenatus tergeminus, and Sistrurus catenatus edwardsi) did not emit more tongue flicks in an environment containing mouse odors than in a control environment. Hence, the vomeronasal systems of these rattlesnakes were not activated by olfactory cues. A hypothesis is offered about the conditions required to stimulate tongue flicking in rattlesnakes.

Investigatory behavior inthe plains garter snake (Thamnophis radix) and several additional species

Garter snakes (Thamnophis radix), hognose snakes (Heterodon platyrhinos), and rattlesnakes (Crotalus species) flick their tongues and crawl about in an open field containing no food or sexual (i.e., reproductive) odors. As Experiment I shows, the taxa differ reliably in both rate of tongue flicking and rate of locomotion. In Experiment II, garter snakes (Thamnophis radix) placed into an open field for 5 min showed more tongue flicking than snakes that were handled and placed directly back into their home cages, indicating that the first group was exploring the apparatus rather than responding only to handling. During Minutes 3 through 5 (Experiment III) in the open field, garter snakes emitted fewer tongue flicks than they did during the first minute, and after 20 min, the rate of tongue flicking was virtually zero. However, snakes were capable of responding to presentation of new objects and/or odors, indicating that the previous response decrement was not derived from effector fatigue but rather from some habituatory process. Experiment IV revealed that satiated snakes habituated more rapidly than hungry snakes during exploration of the open field. Hence, exploratory behavior in these snakes is at least partially under the control of the same factors which mediate food-related appetitive activities.

Can tongue flicks be used to measure niche sizes?

Competition between animal species is often inferred from a demonstration of niche 'shift' in one or both species. In snakes, potential niches along the food-type dimension may be measurable in terms of responses of naive young snakes to chemical stimuli of various prey types. If responses differ markedly from actual food habits in the wild, diet shift due to competition may be implied. This approach was used on naive young of three species of garter snakes (Thamnophis) that coexist on Vancouver Island. Responses to stimuli, measured as numbers of tongue flicks per minute, were generally strong to prey normally eaten in the field, but strong responses to unusual prey items were also noted. No two species responded identically to all the stimuli used. The diets of two of the species are possibly determined in part by competition between them. Various weaknesses of this method and other interpretations of results are discussed.

Rate of tongue flicking by rattlesnakes during successive stages of feeding on rodent prey

Specimens of each of three species of rattlesnakes (Crotalus enyo enyo, C. durissus culminatus, and Crotalus vegrandis) exhibited no tongue flicking prior to striking live mice during a regular feeding session. All snakes flicked their tongues at high rates (more than 20 flicks/minute) between striking and commencement of swallowing. Also, frequent tongue flicking (10 to 15 flicks/minute) was seen for about 15 min after swallowing. These data indicate that well-acclimated, captive rattlesnakes do not rely upon the Jacobson’s organ to detect prey or to guide the predatory attack, but that they do use this sensory system to locate prey after striking. Since an envenomated rodent may wander several meters prior to dying, Jacobson’s organ may be very important in finding such prey. It is also of interest that renewed tongue flicking occurs after swallowing. A hypothesis is offered concerning the role of the latter behavior.

Reliability of individual differences between garter snakes (Thamnophis radix) during repeated exposures to an open field

Eight garter snakes (Thamnophis radix) were observed during 10 daily 10-min sessions in an open field, and minute-by-minute records were kept of the frequency of tongue flicking and square traversing. The behavior of the snakes indicated that they were exploring the apparatus, and considerable individual differences were evidenced in both dependent variables. Correlational analyses compared the daily pattern of individual differences for each measure with the patterns on each other day; individual differences in each measure were found to be reliable. An interpretation of tongue flick rate is offered which suggests that this behavior may represent either an index of obligatory information gathering made necessary by a need for stimulus redundancy or an index of information processing capacity.

Role of the tongue and senses in feeding of naive and experienced garter snakes

Prey attack behavior was studied in two species of garter snakes ( Thamnophis sirtalis and T. radix). Newborn, ingestively naive, and experienced snakes had their tongues severed surgically, while control groups retained their tongues. Attack latency, tongue flick frequency and an orientation-interest measure were recorded for each subject on responses to extracts prepared from species-characteristic prey. Feeding, as well as responses to prey extracts, were found to be suppressed almost totally in the tongueless naive snakes. A detongued adult, however, readily ate although its behavior was abnormal. Temporary blind and anosmic conditions did not have a significant effect on response rates of the tongueless or control groups. While importance of the tongue-Jacobson's organ system is demonstrated, the length of tongue removed and presurgery experience are important factors.

Chemical prey preference polymorphism in newborn garter snakes Thamnophis sirtalis.

AbstractNewborn, previously unfed garter snakes (Thamnophis sirtalis) respond with prey attack and tongue flicking to water based extracts prepared from the surface substances of normally eaten prey and presented on cotton swabs. The present experiments demonstrate reliable individual differences in preferred stimuli among members of the same litter. (I) Of 12 snakes tested on six different days with redworm extract, minnow extract, and distilled water, six responded reliably more to worm and one reliably more to minnow. Redworm was overall more effective than minnow. Using two ranking procedures, individual responsivity to redworm was not correlated with responsivity to minnow. Although distilled water was relatively ineffective, correlations of individual snake scores to extracts and water were high and often significant, in contrast to the low correlations between extracts. (2) Of an entire litter of 13 snakes tested on seven days with extracts from two species of earthworms and two species of fish, 11 responded significantly more to worm extracts and one significantly more to fish extracts. The two worm extracts gave almost identical overall scores and the same occurred for the two fish extracts, with the worm being more effective. While individual responsivities to the two worm or two fish extracts were highly correlated, responsivities across worms and fish were not. A few snakes discriminated between individual worm or fish extracts. (3) In 15 sibling newborn snakes tested on three concentrations (100%, 10%, 1%) of earthworm and fish extracts, most responded more to worm regardless of concentration, a 1% worm extract being more effective than 100% fish. The method of limits was used in both ascending and descending sequences. (4) In all three litters, the snakes could be divided into a few discrete groups based on the relative preference for fish or worm extracts. However, there was wide individual variation in attack frequency, attack latency, and tongue flicking in absence of prey attack. (5) The results are discussed in terms of a genetically based perceptual polymorphism. The phenomenon's possible role in the natural history and evolution of snakes, especially the interaction with feeding experience, is elaborated.

Laboratory observations of trailing behavior in garter snakes.

Using a Y-maze apparatus, nine garter snakes were trained to follow an earthworm-extract trail. Correct trailing improved significantly as training progressed. All snakes were able to attain a trailing criterion of 8 out of 10 correct trials by the termination of training. For each trial, the number of tongue flicks each snake made was recorded and tongue flick rate calculated. Tongue flick rate was found to be highly characteristic and constant for individual subjects. In addition, running speed and tongue flick rate were found to be significantly correlated.

The effects of feeding experience on the response to prey-object extracts in rat snakes

The effect of eating mice over an 8-month period was observed to produce a greater response to mouse body surface extract in young rat snakes (Elaphe). Two measures, attack tongue flick and attack orientation, were employed. This finding was contrasted with earlier results indicating a wide-spectrum undifferentiated response to prey-object extracts at birth.

Effects of deprivation on the tongue flicking and orientation of young rat snakes to water

Young rat snakes (Elaphe) were deprived of water for 6 days and then tested by placing a dry cotton swab and a swab dipped in distilled water 1 cm in front of the snake’s snout. Two measures, approach/tongue flick and approach orientation, revealed that the water elicited higher responding than the dry stimulus. The Ss were then tested over a 10-day period. The stimulating effectiveness of water under deprivation was found to decline at first and then increase until ad lib water was returned. It was concluded that water is an effective stimulus for the snake’s chemoreceptors but would elicit responding only under conditions of deprivation.

Intraspecific Geographical Variation in Chemical Food Cue Preferences of Newborn Garter Snakes (Thamnophis Sir Talis)

AbstractFour litters of garter snakes (Thamnophis sirtalis) born to females captured in three different geographic areas were tested on their responses to an identical series of water extracts prepared from the surface substances of 15 small animals in addition to a distilled water control. Two of the litters came from northern Illinois; the others were from western Iowa and northern Wisconsin. From each litter 21 previously unfed snakes were tested on the fourth and fifth days after birth. The stimuli were presented on cotton swabs, and the number of tongue flicks, as well as attacks and their latencies, were recorded. The four litters shared a basic similarity in the kinds of extracts attacked. However, the relative effectiveness of the extracts varied considerably with the two Illinois litters most alike in their "ranking" of the various stimuli. Thus, geographical differences in responses to chemical cues within a species were shown. A good example of this was seen in the responses to the fish and earthworm extracts. While the two Illinois litters attacked both frequently, the Wisconsin litter attacked the fish much more than the worms and vice-versa for the Iowa litter. Correlations between the various response measures are presented also.

Comparative Prey-Attack Studies in Newborn Snakes of the Genus Thamnophis

Garter snakes (Thamnophis) from five species (including three subspecies of one form) were tested several days after birth with water extracts of at least 12 small animals (1.5 g animal to 10 ccm warm distilled water). The 12 prey animals included three species of earthworms and three of fish, a salamander and its larva, a frog, a leech, a slug and a baby mouse. A distilled water swab elicited tongue flicking only, while certain extract swabs resulted in actual prey-attack behavior after at least one tongue flick. A score was given to each extract test using a simple formula based upon tongue flick frequency and attack latency. Differences and similarities between the species were found and are discussed in relation to the actual feeding preferences in nature and captivity. For example, the aquatic Thamnophis elegans aquaticus attacked only the extracts made from the salamander larva, the frog, and the three fish; Thamnophis sirtalis also attacked the leech and the three earthworm extracts. It is suggested that the perceptual selectivity shown by naive snakes is an evolutionary response to present and past ecological conditions. The ability of newborn snakes to rapidly acquire a food avoidance response was also demonstrated.

Chemical-cue preferences of inexperienced snakes: comparative aspects.

Different species of new-born, previously unfed snakes will respond with tongue flicking and prey-attack behavior to water extracts of the skin substances of various small animals. However, there are clear species differences in the type of extract responded to by previously unfed snakes, even within the same genus. These differences correspond to the normal feeding preferences shown by the various species.