Stimulus control of antipredator behavior in newborn and juvenile garter snakes (Thamnophis).

Used neonate and juvenile garter snakes (Thamnophis sirtalis, T. melanogaster, and T. butleri) to investigate the role of visual stimuli in mediating antipredator behaviors and to examine the validity of techniques used to assess defensive responses. Experiment 1 demonstrated that a human hand and a model predator were more effective than other stimuli in eliciting defensive responses in neonates with no prior experience with threatening stimuli. Experiment 2 showed that yearlings responded similarly to a realistic predator model and a human hand. Experiment 3 showed that the level of antipredator behaviors was affected by stimulus size. Experiment 4 indicated that the same snakes gave similar quantitative results when tested by different experimenters with the human hand. The final study demonstrated that stimulus movement influenced defensive responses in some species but not others and found litter and experiential effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experiential modification of defensive behaviors in garter snakes (Thamnophis sirtalis).

Modification of defensive behavior of garter snakes (Thamnophis sirtalis) was examined. In Exp 1, 56 juvenile snakes from 7 litters were divided into 3 groups and exposed to either regular harassment with a predator model, gentle handling, or no treatment. Behavioral tests showed significant group differences in the number of strikes directed at the predator model and evidence of a Litter?×?Treatment Condition interaction. In Exp 2, 45 of the animals from Exp 1 were given a 2nd series of treatments in a within-subjects design. The results (1) replicated the 1st experiment, (2) indicated that the elevated strike scores found in Exp 1 were relatively long-lasting, and (3) showed that increased strike scores were not due to ontogenetic changes in reacting to stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strike-induced chemosensory searching by ingestively naive garter snakes (Thamnophis sirtalis).

Neonatal, previously unfed garter snakes exposed to aqueous chemical cues from earthworms tongue flicked at higher rates during the 5 min after withdrawal of the stimulus than after aqueous control trials. If snakes struck at but did not touch the worm stimulus, they showed a much greater increase over control trials in postexposure tongue flicking than when they did not strike, and the increased rate persisted longer. These results demonstrate strike-induced chemosensory searching (SICS) by ingestively naive snakes. It is highly probable that other squamate reptiles show a similar well-integrated suite of sequential foraging behaviors at birth or hatching. Differences among species in SICS may be related to details of sequential prey capture tactics in reconstruction of phylogenetic patterns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned discrimination of airborne odorants by garter snakes (Thamnophis radis and T. sirtalis sirtalis).

For snakes, the nasal chemical senses are critical in intraspecific communication and prey recognition. Although it is known that garter snakes can respond differentially to airborne odorants, no previous study has demonstrated that snakes can learn a task with airborne odors as discriminative stimuli. In Experiment 1, 7 plains garter snakes (Thamnophis radix) were trained in a two-choice apparatus to move into a compartment containing lemon-scented chips for a food reward. All 7 snakes improved performance when the first 10 and last 10 trials of the 100 trials of conditioning were compared. Four of the snakes were subsequently trained to move away from the scented compartment into the unscented compartment. The 4 snakes rapidly learned this reversal. In Experiment 2, 7 common garter snakes (T. sirtalis sirtalis) were trained to traverse a two-choice maze with the presence or absence of amyl acetate odor as the conditioned stimulus. The snakes were pretested for odor versus nonodor preference and were trained to go to the initially nonpreferred stimulus. Of the 7 snakes, 5 achieved a predetermined criterion (two training sessions with cumulative correct responding above the .05 confidence level) within 85 trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social dynamics of group courtship behavior in male red-sided garter snakes (Thamnophis sirtalis parietalis).

Examined the social dynamics of the formation of mating balls (gatherings of males) during the mating period of red-sided garter snakes to determine whether the mating balls are formed simply because of a common attraction to the female or whether males are stimulated by the mating balls themselves. Nine test males and 9 stimulus females were used in tests, along with 55 other males, to measure the effect of other courting males. Results show that male Ss courted females more actively when other males were also courting the female than when they were alone with her, suggesting that the female is more attractive to the male when courted by other males. A positive correlation was observed between the number of additional males present and the amount of courtship activity shown by the test male toward the stimulus female. The extent to which the courtship activity of the test males was stimulated by the presence of additional courting males was not influenced by how actively the additional males courted. Results suggest that males are intrinsically stimulated by mating balls. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of antipredator responses in snakes: II. Effects of recent feeding on defensive behaviors of juvenile garter snakes (Thamnophis sirtalis).

The effect of having eaten a large meal (50% of body weight) on the defensive behavior of juvenile garter snakes (Thamnophis sirtalis) was investigated. Twenty-five 10-wk-old snakes were tested for antipredator responses (strikes) directed toward a threatening stimulus (moving and nonmoving human hand) before and after having eaten a large worm segment. Snakes directed significantly (p?     

Differential effects of courtship and mating on receptivity and brain metabolism in female red-sided garter snakes (Thamnophis sirtalis pareitalis).

In the female red-sided garter snake (Thamnophis sirtalis parietalis), the loss of receptivity following intromission during mating can be prevented by injection of a local anesthetic (tetracaine) in the cloacal region prior to courtship and mating. Females that were courted and then mated had significantly higher uptake of radio-labeled [1?C]2-fluoro-2-deoxyglucose (2-DG) in the preoptic area (25%) and significantly lower uptake in the ventromedial hypothalamus (-20%) compared with females that were courted but not mated. Tetracaine-treated females had accumulation patterns similar to courted but unmated females and to females exposed only to other females. These results suggest that in the female red-sided garter snake, sensory input from the cloaca during mating alters patterns of metabolism in those brain areas most often associated with female sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonate plains garter snakes (Thamnophis radix) are attracted to conspecific skin extracts.

Several species of snakes aggregate in areas previously marked by conspecifics. However, species differences and sources of such chemical signals have received little attention. Methylene chloride-soluble substances from shed epidermis of adult plains garter snakes attracted neonate conspecifics, whereas similar extracts from a congener and a viperid did not. The functional significance of such conspecific aggregation may relate to location of hibernacula, foraging areas, osmoregulation, or predation avoidance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of lingual predatory luring and related foraging tactics of mangrove saltmarsh snakes (nerodia clarkii compressicauda).

Knowledge of the various cues that elicit natural behavior is important to our understanding of why and when animals behave as they do. In order to gain insight into the behavior and ecology of Nerodia clarkii compressicauda, a piscivorous snake that uses a unique form of predatory luring as a foraging tactic, we observed 22 juvenile subjects in the presence of visual and chemical prey stimuli in a repeated-measures design. The use of video playback as a visual stimulus in this experiment permitted complete isolation from tactile and chemical cues. Snakes were more sedentary and used lingual luring more when both cue types were present than when none or only one of the cues was available. Subjects also attacked more often in the presence of both stimuli. Predatory attacks by prey-na?ve subjects directed to video cues when only visual prey stimuli were available demonstrated that snakes can identify prey visually without prior experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immobility and supination in garter snakes (Thamnophis elegans) following handling by human predators.

A common response of animals to physical restraint is tonic immobility. The authors observed the behavior of garter snakes, Thamnophis elegans, in the field to determine the frequency of immobility as a response to handling. Most snakes fled after release, but the remainder remained immobile, sometimes on their backs (supination), for up to 10 min. Immobility was seen most often in pregnant snakes, which also were more likely than other snakes not to have moved before capture. Failure to move, either before or after capture, might be a consequence of the limited locomotory ability of gravid snakes. However, the lack of observations of interactions between snakes and their natural predators impedes researchers' understanding of the antipredator value, if any, of tonic immobility. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Plasticity of foraging behavior in garter snakes (Thamnophis sirtalis) reared on different diets.

The ontogeny of foraging was studied in 107 neonatal garter snakes (Thamnophis sirtalis) reared on 3 different diets: fish, leafworms, or mixed. Times to approach, capture, handle, and swallow prey were measured during each snake's first feeding and again after 11 to 12 meals. Overall times to consume prey decreased between the first and last tests for the 3 groups, but both prey type and the relative amounts of prey consumed differentially affected the various feeding phases. Approach latencies significantly decreased for snakes fed worms or fish exclusively but not for the mixed-diet snakes. The degrees to which capturing and swallowing latencies decreased differed among diet groups. Diet had little effect on prey handling duration. Sex and litter effects were reduced after feeding experience. These results reveal flexibility in feeding behavior as well as the costs and benefits of experience with multiple prey classes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Laboratory observations of aggregative behavior of garter snakes, Thamnophis sirtalis..

In 4 experiments, 176 male garter snakes, tested in groups of 8, established preferred shelter locations and reliably returned to these locations as a group or as individuals when the test aquaria were left undisturbed between trials. When the aquaria were cleaned and the contents replaced on each trial, preferred shelter locations were not established over trials; however, Ss were found under shelters in large aggregates more frequently than would be expected by chance. It appears that the snakes deposit cues in the apparatus that are subsequently used to return to preferred locations. Manipulations of various objects in the test arena indicated that the relevant cues were deposited on the paper underlying the preferred shelter. (59 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of antipredator responses in snakes: I. Defensive and open-field behaviors in newborns and adults of three species of garter snakes (Thamnophis melanogaster, T. sirtalis, T. butleri).

A comparative study of defensive behavior in multiple litters of newborn garter snakes and adult female garter snakes from 3 species was conducted in the laboratory. In Exp I, 241 1-day-old Ss, roughly equally divided among the 3 species, were tested for defensive behaviors directed toward a moving or nonmoving stimulus. T. melanogaster babies were the most reactive in terms of strikes, bites, and defensive tongue flicks. T. sirtalis and T. butleri were less reactive and not significantly different from each other. In Exp II, 32 adult females reacted in ways similar to the neonates, except that the T. sirtalis females were more reactive toward the moving stimulus than were the T. butleri females. Exp III showed large and significant differences in open-field behavior among the newborn of the 3 species but few significant correlations between open-field measures and antipredator responses. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of predatory behaviors of deer mice (Peromyscus maniculatus) and grasshopper mice (Onychomys leucogaster).

Deer mice (Peromyscus maniculatus) and grasshopper mice (Onychomys leucogaster) are morphologically similar and coexist in many habitats. I compared certain aspects of their insect-catching behavior for insights into the ecology and evolution of predatory behavior in rodents. The predatory attack of grasshopper mice appears more specialized than that of deer mice: The former attacked faster and more consistently, used their paws more to seize a fast-moving prey, and showed more resistance to the inhibitory effects of novel, aversive, or intimidating stimuli from a prey than did the latter. Nonetheless, deer mice are effective insect predators and exhibit a more developed predatory attack than hamsters, whose attack response is considered typical of many rodents. Grasshopper mice exhibit behavioral and morphological adaptations expected of a carnivorous mammal, and these adaptations also aid in its competition for insect prey with other rodents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral development: Nest emergence of young pine snakes (Pituophus melanoleucus).

Examined the activity patterns and emergence behavior of 17 pine snake young hatched in the laboratory in 4 experiments. Because pine snake young hatch in a nest below the ground, it was predicted they would be inactive until shedding, and following shedding they would become active, begin to climb upward, and decrease their entrance into tunnels. Results show that prior to shedding, young Ss were inactive, readily entered a tunnel, and did not climb. After shedding, the young were less likely to enter a tunnel, became active all day, and climbed upward. Tests with an artificial nest chamber demonstrated that most young dug or pushed their way out of a burrow. It is suggested that timing of emergence is related to shedding rather than hunger since emergence behaviors increased after shedding, and eating did not directly follow shedding or depress these behaviors. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of defensive behaviors of garter snakes (Thamnophis sirtalis): Effects of eye spots and movement.

The purpose of these experiments was to examine the effects of eye spots and stimulus movement as mediators of antipredator responses in garter snakes. In Experiment 1, 13 Eastern garter snakes (Thamnophis sirtalis) at 6–8 weeks of age were confronted with a series of threatening models that varied in the configuration of the eyes (artificial glass eyes, circular black spots, elongated black bars, or no eyespots). There were significant differences in the number of strikes elicited by the models, and the model with realistic glass eyes elicited the most strikes. In Experiment 2, we examined the effects of erratic and consistent stimulus movement on defensive behavior in 12 garter snakes at 12–26 weeks of age. The snakes delivered significantly more strikes to an erratically moving model than to a model oscillated at a regular rate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses to quantity: Perceptual versus cognitive mechanisms in chimpanzees (Pan troglodytes).

Two chimpanzees were trained to select among 2 different amounts of candy (1–6 items). The task was designed so that selection of either array by the active (selector) chimpanzee resulted in that array being given to the passive (observer) animal, with the remaining (nonselected) array going to the selector. Neither animal was able to select consistently the smaller array, which would reap the larger reward. Rather, both animals preferentially selected the larger array, thereby receiving the smaller number of reinforcers. When Arabic numerals were substituted for the food arrays, however, the selector animal evidenced more optimal performance, immediately selecting the smaller numeral and thus receiving the larger reward. These findings suggest that a basic predisposition to respond to the perceptual motivational features of incentive stimuli can interfere with task performance and that this interference can be overridden when abstract symbols serve as choice stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization in a predatory rodent, the northern grasshopper mouse (Onychomys leucogaster).

A comparison of the ability of mammals to localize sound revealed that among the animals examined to date, none of the rodents have been able to localize as accurately as the carnivores. Because all of these rodents are prey animals, the question arises as to whether their poor localization acuity is a phyletic trait of Rodentia or whether it is a trait common to prey species that may be under less selective pressure than predators to localize sound accurately. To answer this question, sound localization acuity was determined in a species that is both predatory and a rodent, the northern grasshopper mouse. Localization thresholds for a single 100-ms noise burst were determined for three grasshopper mice using a conditioned avoidance procedure. Their 50% discrimination threshold of 19° is larger than that of any of the previously tested carnivores and well within the range of other rodents. However, calculations of the binaural sound localization cues available to rodents (based on their head size) suggest that the grasshopper mouse may make more efficient use of the available locus cues than other rodents. Thus, although the grasshopper mouse cannot localize as accurately as carnivores, it appears to be more accurate than predicted for a nonpredatory rodent of its size. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of poisoning on predatory and ingestive behavior toward artificial prey in rats (Rattus norvegicus).

Ingestion of novel prey by vertebrate predators that is followed by illness typically decreases the predators' eating the prey more readily than their pursuing or killing it. We used artificial prey-food items (rolling ball bearings that predicted food pellets) to model and extend this finding in laboratory rats. During daily experimental sessions presentations of a novel bearing–food combination were intermixed with presentations of a familiar bearing–food combination. The poisoned animals received lithium chloride injections after each session. Poisoning markedly decreased ingestion of the novel food without decreasing the frequency of contact (nose, seize, carry, or chew) with the novel bearing predicting that food. However, poisoning did significantly decrease the average duration of contact with the novel bearing. Poisoning did not decrease behavior toward the familiar food and bearing. After moderate exposure to pairings of the novel food and bearing, poisoning decreased behavior toward both novel and familiar food and bearings. The results indicate that important aspects of predation can be simulated and examined in the laboratory by using artificial prey-food items. These results also support the conclusions that predatory behavior and ingestion reflect separable modes of behavior and that the presence of novel prey interferes with the generalization of poisoning effects to familiar prey. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of toxicosis on the predatory behavior of the golden hamster (Mesocricetus auratus).

Two experiments attempted to measure the effects that toxicosis had on the golden hamster's predatory behavior and to compare these results with those found in previous studies with grasshopper mice. In Exp I (n?=?17), a 0.15 M LiCl ip injection caused Ss to develop a greater aversion and to inhibit their feeding and attack responses more frequently toward a house cricket than did a similar injection of NaCl. In Exp II (n?=?13), the added presence of an almond coating on the cricket prolonged the number of days that a hamster exhibited an aversion toward the prey and an inhibition to attack. Essentially, the inhibitory effects from toxicosis in the hamster paralleled those found with the grasshopper mouse by W. M. Langley (see record 1982-20395-001) and Langley and K. Knapp (see record 1984-00491-001). The differences in these inhibitory effects are attributed to inherent differences in the attack responses of the 2 rodents. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)