Temperature activation of courtship behavior in the male red-sided garter snake (Thamnophis sirtalis parietalis): Role of the anterior hypothalamus-preoptic area.

Adult male red-sided garter snakes (Thamnophis sirtalis parietalis) received radio-frequency lesions prior to 17 weeks of low-temperature hibernation. Animals found to have bilateral lesions of the anterior hypothalamus-preoptic area ({ah-poa}) failed to exhibit courtship behavior on emergence from hibernation. Those individuals in which the major portion of the destruction was centered in the anterior POA also exhibited deficits in thermoregulatory behavior. Animals that received unilateral lesions of the {ah-poa} initiated courtship behavior after controls and had an abbreviated period of courtship; these animals exhibited normal responses to thermal stimuli. Male snakes with lesions outside the {ah-poa} courted normally and demonstrated no differences in thermoregulatory behavior compared with the surgical controls. These results indicate that in male red-sided garter snakes, an intact {ah-poa} is critical for the integration of thermal stimuli that activate seasonal courtship behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Role of the anterior hypothalamus–preoptic area in the regulation of courtship behavior in the male Canadian red-sided garter snake (Thamnophis sirtalis parietalis): Lesion experiments.

Lesions of the medial preoptic area and/or the ventromedial hypothalamus resulted in an abrupt and immediate decline in courtship behavior in 28 male Canadian red-sided garter snakes. Lesions of the more anterior portions of the preoptic area resulted in a more gradual, delayed decline in courtship behavior. Ss sustaining lesions dorsal, ventral, or caudal to the anterior hypothalamus–preoptic area (AH–POA) exhibited no change in courtship behavior relative to controls. Measurements of testis size, spermatogenic stage, and circulation levels of androgens revealed no differences between any of the groups. There were marked differences in the change in hematocrit over time between the groups. Results indicate that the AH–POA is involved in the control of courtship behavior in the adult male red-sided garter snake. Moreover, it is suggested that the stimulus affecting the AH–POA to activate courtship is temperature-related. (32 ref) (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)     

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)     

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)     

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)     

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?     

Courting and noncourting male red-sided garter snakes, Thamnophis sirtalis parietalis: plasma melatonin levels and the effects of pinealectomy

Previous studies found that pinealectomy of male Canadian red-sided garter snakes (Thamnophis sirtalis parietalis) in the autumn, before prolonged exposure to low temperatures (hibernation), significantly impaired the expression of courtship behavior upon emergence in the spring. Additionally, pinealectomized animals with a disrupted diel cycle of plasma melatonin did not court while those exhibiting a more typical diel pattern did. These results suggested that the pineal gland functions in the transduction of a temperature cue which stimulates courtship. To test this hypothesis, we pinealectomized males in the spring after they had undergone a normal hibernation but were still courting. Pinealectomy of courting males in the spring, in each of the 3 years of study, had no effect on courtship. This result suggests that once the cue is transduced, the pineal gland no longer has a modulatory effect on courtship behavior. Finally, we took advantage of the fact that, in the laboratory, there is always a small percentage of males that do not court upon emergence. Pinealectomy of these noncourters greatly increased the percent of males expressing courtship behavior in each of the study years. Plasma melatonin levels of unmanipulated courting and noncourting males was measured after emergence in successive years. In both years, courters had a typical pattern of melatonin secretion (low in the photophase, high in the scotophase) while persistent noncourters displayed the opposite pattern.     

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)     

Roles of the vomeronasal and olfactory systems in courtship behavior of male garter snakes.

Studied whether male garter snakes required intact vomeronasal or olfactory systems to detect the pheromone that triggers the chin-pressing behavior of courtship. Male garter snakes with testosterone propionate pellets implanted sc were tested for courtship displays with estradiol-benzoate-treated females. Three groups of 10 males were formed from snakes exhibiting strong courtship responses. Bilateral olfactory nerve cuts were attempted on 1 group, vomeronasal nerve cuts on a 2nd, and control surgeries on a 3rd. All snakes in the olfactory nerve cut and control groups courted after surgery, and 3 snakes in each group copulated. More than half of the snakes in the olfactory nerve cut group had complete nerve cuts. Nine of the 10 snakes in the vomeronasal nerve cut group exhibited no courtship responses after surgery. The 1 snake in this group that courted was the only snake in which intact vomeronasal nerve fascicles were observed. Data indicate that male garter snakes without functional olfactory systems do court and mate normally, but that male garter snakes without functional vomeronasal systems exhibit no courtship responses. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mortality in red-sided garter snakes, Thamnophis sirtalis parietalis, due to larval nematode, Eustrongylides sp

Garter snakes, Thamnophis sirtalis parietalis, that had been fed wild-caught banded killifish, Fundulus diaphanus, and laboratory-bred leopard frogs, Rana pipiens, were infected by larval nematode, Eustrongylides sp; 7 of the 25 snakes died. Signs of infection in 20 snakes included subcutaneous "lumps," violent contortions, and bloody exudate, apparently from the nares. Nemotodes were collected at necropsy from beneath the skin, in the lungs, in the body cavity, and along the spinal column. Nematodes were surgically removed from subcutaneous sites in 2 garter snakes, which recovered completely.     

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)     

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)     

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)     

Responses to escalating predatory threat in garter and ribbon snakes (Thamnophis).

Several models suggest that animals perform a stable sequence of responses during increasing threat from a potential predator. To test the comparative utility of such models, 45 garter and ribbon snakes from 4 species were given an antipredator behavior test in which the snakes were exposed to a series of 5 levels of escalating threat: (1) threat is out of view, (2) threat looms over arena, (3) threat is nonmoving human hand near snake's head, (4) threat is moving human hand, and (5) threat is experimenter's tapping the snake's body. Five different antipredator behaviors were measured. It was found that both qualitative and quantitative changes in behavior occurred between threat levels. However, species differences were also found in the occurrence and amount of every behavior recorded, which indicates that even closely related species may differ in behaviors exhibited in different phases of a predatory encounter. (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)     

Laboratory observations of aggregative behavior of garter snakes, Thamnophis sirtalis: Roles of the visual, olfactory, and vomeronasal senses.

Two experiments determined (a) whether male garter snakes require a functional vomeronasal or olfactory system to return to previously preferred shelter locations and (b) the sensory modalities used to aggregate in the absence of previously deposited chemical cues. In Exp I, 22 male garter snakes with vomeronasal nerve lesions did not return to previously preferred shelter locations when tested individually. However, when tested with a group that included 9 control Ss, they returned to previously preferred shelters. The shelter-selection behavior of Ss with olfactory nerve lesions improved postoperatively, whereas the behavior of Ss with sham lesions was unchanged. In Exp II, 32 Ss were tested for aggregation in aquaria in which the substrate and other contents were cleaned between trials. After blindfolding or olfactory nerve cuts, Ss aggregated at normal levels. When Ss' vomeronasal ducts were sutured closed, aggregation scores were significantly depressed, although 2 of the 3 groups with vomeronasal duct sutures did aggregate just above change levels. Results from both studies indicate that use of chemical signals by garter snakes in shelter selection and aggregation is mediated by the vomeronasal system and that neither the olfactory nor the visual system is critical for these behaviors. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hormones and midbrain mediation of courtship behavior in the male ring dove (Streptopelia risoria).

Investigated the possible role of the intercollicularis (ICo) region in the androgen-dependent courtship behavior of male ring doves. In Exp I, bilateral lesions in the ICo region reduced nest-cooing but did not specifically alter other courtship behavior of males tested with stimulus females. In Exp II, unilateral implants containing crystalline testosterone propionate (TP) or cholesterol (C) were placed in the ICo region or in other parts of the midbrain of castrated Ss. The TP implants activatad nest-cooing only when placed in the ICo region. Diffusion from the implant was probably not responsible for the elicitation of nest-cooing, since the weights of the peripheral steroid-sensitive tissues of Ss implanted with TP and C did not differ and since many sites near, but not in, the ICo region were ineffective. Data demonstrate the importance of the ICo region in the expression of courtship behavior in the male ring dove. The facilitation of certain vocal courtship behavior by hormonal stimulation is in line with the suggestion that the central gray/ICo/torus semicircularis regions of the vertebrate brain are analogous in their mediation of vocalizations. (58 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)