Behavior Of Snakes Research Articles

Sexual behavior and 2-deoxyglucose uptake in male red-sided garter snakes (Thamnophis sirtalis parietalis).

The [14C]2-deoxyglucose (2-DG) technique was used to study patterns of neural activity associated with the species-typical courtship behavior of male red-sided garter snakes (Thamnophis sirtalis parietalis). Males in this species court females intensely during the first month following spring emergence from their prolonged winter hibernation. Autoradiographic methods were used to measure the accumulation of radioactive label in various regions through the brains of male garter snakes that courted females, males that failed to court females, and males not exposed to females. Male garter snakes that actively courted females showed a pronounced increase in 2-DG accumulation, and therefore presumably neural activity, in the region of the anterior hypothalamus/preoptic area, relative to males that did not actively court females. Males exposed to females (regardless of whether they courted or not) showed widespread, non-specific increases in 2-DG uptake relative to males not exposed to females. The results indicate the utility of the 2-DG technique for studying complex, species-typical behaviors in vertebrates.

Spatial Patterns in Tiger Snakes (Notechis ater: Elapidae) on Offshore Islands of Southern Australia

Dispersion was studied in four island populations of tiger snakes (Notechis ater) in southern Australia. Within islands, snakes were usually aggregated in areas of high densities of prey and/or cover. Differences in the dispersion patterns of snakes among islands were correlated with differences in the spatial distributions of these resources. On an island where both resources were abundant and randomly spaced, snakes were also randomly dispersed. The evidence supports the hypothesis that resource densities are important determinants of dispersion in island tiger snakes and may have contributed to evolutionary divergence in these populations. l of erpetology, Vol. 25, No. 3, pp. 278-283, 1991 i t 1991 Society for the Study of Amph bians and Reptiles l atterns in Tiger Snakes (Notechis ater. Elapidae) on Dispersion is the spatial pattern of individuals within a population, and has been much studied (e.g., Hutchinson, 1953; Odum, 1959; Brown and Orians, 1970; Pielou, 1977; Brower and Zar, 1984). Individuals can be dispersed randomly, evenly, or clumped. In population ecology most sampling methods (particularly mark-recapture models) assume equal catchability and random distributions of individuals (Caughley, 1977; Krebs, 1989). However, these assumptions are in many cases incorrect. Mat1 Present Address: Alabama School of Mathematics and Science, P.O. Box 161628, Mobile, Alabama 366162628, USA. i is the spatial pa tern of individi i a population, and has been much (e. ., Hutchinson, 1953; Odum, 1959; ing systems, predator-to-prey ratios, territoriality, and survivability are influenced by spatial patterns, perhaps more than simply by density values (Brower and Zar, 1984). For snakes, dispersion has never been explicitly studied in the field (see review by Gregory et al., 1987). However, numerous published observations on snake ecology suggest, a priori, that random distributions should not occur because snakes are mobile organisms whose critical resources (e.g., food, shelter, basking sites) would not be expected to be homogeneous in any given habitat. Although there are few studies on the social behavior of snakes (Leyhausen, 1965), and some authors have concluded that snakes are solitary s, predator-to-prey ratios, te ritorisurvivability are influenced by spatial , erhaps ore than simply by density ( er and Zar, 1984). s, dispersion has never b en ext ied in the field (s e review by Gregl., 1987). However, numerous published i s on snake ecology su gest, a priori, 278 This content downloaded from 157.55.39.215 on Wed, 31 Aug 2016 05:10:57 UTC All use subject to http://about.jstor.org/terms SPATIAL PATTERNS IN ISLAND TIGER SNAKES or asocial (e.g., Brattstrom, 1974), male-male combat (Shine, 1978), mating behavior, and seasonal aggregations qualify snakes as social animals. Interactions that influence dispersion patterns among conspecifics can in turn limit prey types or lead to differential mating success, perhaps resulting in differentiation of populations (Stamps, 1977; Case, 1982; Stamps and Buechner, 1985). During mark-recapture studies of black tiger snakes (Notechis ater) on several offshore islands in southern Australia (Schwaner, 1985, 1989; Schwaner and Sarre, 1988), spatial patterns of individuals were quantified. Dispersion in each population was compared with similar measurements of two essential resources, prey and cover, to determine how these parameters were correlated within each island. Given that types of prey and cover differed (Schwaner, 1985), were these patterns and their relationships similar among islands?

The Role of Sensory Receptors in the Predatory Behavior of the Brown Tree Snake, Boiga irregularis (Squamata: Colubridae)

The brown tree snake (Boiga irregularis) is indigenous to parts of costal Australia, New Guinea, and the Solomon Islands (McCoy, 1980; Cogger, 1983). It can be found in a variety of habitats (Fritts, 1988), but it is arboreal and most common in primary and secondary growth forests (Savidge, 1986, 1987; Fritts et al., 1987). Its dentition is usually referred to as rear fanged, in which one or two posterior maxillary teeth are enlarged and bear on their labial faces an open groove associated with a connecting duct from Duvernoy's gland. The snakes appear to feed opportunistically: stomach and intestinal content analyses reveal a diet of birds and their eggs, lizards and their eggs, and small mammals (Savidge, 1988). The diets of males and females are the same, but medium to large snakes (over 120 cm SVL) tend to consume a larger proportion of birds, bird eggs, and mammals (Savidge, 1988). They are considered nocturnal in their natural habitat (Fritts, 1988; Chiszar, 1990), an activity continued in captivity (Chiszar et al., 1985). The eyes of the brown tree snake are large and the pupils are slit-like. A vomeronasal organ is present, but like other colubrid snakes, the brown tree snake lacks anatomically distinct thermosensitive facial pits. Eyes, chemosensory receptors (olfactory epithelium, vomeronasal organ), and thermosensitive pits are known to be important in the predatory behavior of certain venomous snakes (de Cock Buning, 1983). When denied visual information, pit vipers can still uccessfully strike prey, presumably by compensating with thermosensitive receptors (Noble and Schmidt, 1937; Dullemeijer, 1961). However, without such alternative sensory receptors the brown tree snake would seem to require alternative sensory input to compensate for loss of visual information during nocturnal forays for food. To assess feeding performance in the absence of visual information, prey capture success of brown tree snakes with and without blindfolds was compared. The purposes of this experiment were to describe the changes in predatory behavior (normal and blindfolded), and to produce hypotheses about how the sensory versatility of the nervous system might modulate the strike based upon alternative routes of sensory input. All brown tree snakes used were collected on Guam.

Nesting Behavior of Pine Snakes (Pituophis m. melanoleucus) in the New Jersey Pine Barrens

We studied the excavation and nesting behavior of pine snakes (Pituophis m. melanoleucus) in the New Jersey Pine Barrens from 1977-1989. Females excavate a tunnel and nest chamber for egg laying. Females initially make slight depressions in the sand (pre-test holes, 22%), then construct small test holes (16%), and finally excavate long tunnels leading to nest burrows (62%). Test holes and nests did not differ in most external characteristics (dump pile size, entrance size), although they did differ in soil moisture at the end of the tunnel, mean tunnel length, and number of turns. Mean clutch size was 9.5 ? 0.3 (range 4-16), and was related to female snout-vent length (r = 0.60, P < 0.001). Female vertebrates exert control over the growth, development, and survival of embryos either by having internal development (i.e., most mammals), impregnable eggs (i.e., most birds),

Trans-seasonal action of androgen in the control of spring courtship behavior in male red-sided garter snakes.

Gonadal steroids have traditionally been found to have short-term effects on the mating behavior of adult vertebrates, such that increased steroid hormone levels influence behavior over the course of a few days. Long-term effects also have been observed in which embryonic exposure to steroid hormone influences the sexual behavior of adults. The generality of the paradigms that have resulted from this work must be viewed with caution as all of the species studied exhibit a particular reproductive pattern. Here it is shown that in the adult red-sided garter snake, the seasonal androgen peak in the summer has a delayed action (8 months) on the male's readiness to court the next spring following emergence from hibernation. This suggests that the interval between the exposure to and the effects of steroid hormones in adult vertebrates may range from short latencies to long latencies and that the present dichotomy of organizing (permanent) versus activating (transient) effects of steroid hormones may not apply in certain instances.

High Predation on Green Snakes, Opheodrys aestivus

In the course of monitoring movements and behavior of gravid green snakes (Opheodrys aestivus) by radiotelemetry, I observed predation by kingsnakes (Lampropeltis getulus) and racers (Coluber constrictor). The high frequency of the observed predation warrants this report. Miniature radio transmitters (220 MHz, Model SOPI1038-LD; Wildlife Materials, Inc.) were implanted into nine large (>500 mm snout-vent length, SVL), gravid 0. aestivus. The snakes were released on 19 June 1988 at the sites of captures made during the previous week in the shoreline vegetation of a small lake 2 km W of Denmark, White County, Arkansas. Snakes were relocated several times each day until oviposition, and at least once each day thereafter. After relocating Opheodrys nos. 255 and 584 several times on 24 June, weak signals were received in the afternoon from each snake indicating extensive movements atypical for the sedentary 0. aestivus. Both signals were emanating from L. getulus (670 mm SVL male; 860 mm SVL female) from which Opheodrys nos. 255 and 584 with implanted transmitters were subsequently palped. On 6 August, signals from Opheodrys no. 5 were received from underground, atypical for the arboreal 0. aestivus. Underground signals continued to be received from no. 5 at various locations within an approximate 30 m2 area over the next 14 days. On 20 August, I dug into a system of rodent burrows at the signal source and eventually found a 720 mm SVL female L. getulus. The Lampropeltis was taken to the laboratory where on 23 August it passed the transmitter originally implanted in Opheodrys no. 5. ' S EY, R. T., AND K. A. BAI . 1987. Asse ment petitive interactions between two iguanid species. Oikos 48(2):206-210. At dusk on 9 July, Opheodrys no. 37 was ovipositing in a hollow tree. The next morning three Opheodrys eggs were found scattered on the ground at the base of the tree and a signal could not be detected. After extensive searching, a signal was detected, eventually leading to a 960 mm SVL female Coluber constrictor. Dissection revealed that the Coluber had first ingested an Opheodrys egg and then ingested Opheodrys no. 37. The posterior gut of the Coluber was full of grasshoppers. Additional observations implicate Coluber as a predator of 0. aestivus during this study. On 24 June, signals from Opheodrys no. 605 were lost. The last contact with the snake had been made the previous day at a ocation within 3 m of an active Coluber. A subsequent search for the Opheodrys was unsuccessful. On two other occasions (22 and 23 July), two different Coluber were observed actively foraging arboreally in the narrow band of alder at the shoreline, the preferred habitat of 0. aestivus (Plummer, 1981). Studies of telemetered Coluber support strong arboreal tendencies (Fitch and Shirer, 1971). At dusk on 7 July, Opheodrys no. 110 retreated into a rotted stump as she moved back toward her activity range after ovipositing in a hollow tree. The next morning, her transmitter was found on the ground next to a large oak tree, but she could not be located. The sutures at the site of implantation were intact on 7 July suggesting that the transmitter was lost as a result of predation, perhaps by a bird or mammal. On several occasions, I and my assistants have observed predation by bluejays (Cyanocitta cristata) on 0. aestivus in an outdoor enclosure (Plummer, unpubl. obs.). Typically, bluejays carried snakes to a tree, pecked them to death, and eviscerated them as they ate. Parts not eaten, including most of the carcass, were allowed t fall to the ground (see also Sledge, 1969; Hammerson, 1988). Mammalian predation would also free the transmitter, but no tooth marks were found on the transmitter.

Courtship of the Garter Snake, Thamnophis marcianus, with a Description of a Female Behavior for Coitus Interruption

Since Gillingham's (1974, 1976, 1977) original works on the breeding behavior of snakes, additional studies have utilized his triphasic model in a variety of snake species (Ford, 1982; Gillingham et al., 1977; Gillingham and Chambers, 1982; Gillingham et al., 1983; Hayes, 1986; Murphy and Barker, 1980; Secor, 1987). However, no such analysis has been applied to the courtship patterns of any species of thamnophine snake. This study catalogues the courtship behavior pattern of the checkered garter snake, Thamnophis marcianus, using a modified version of Gillingham's (1976) male motor patterns. Adult T. marcianus originally collected from La Salle County, Texas, were individually housed in an animal room at the University of Texas at Tyler which ranged from 26-30 C with a photoperiod of 12L:12D. Water was available at all times and the snakes were fed

The colourful behaviour of garter snakes

The colourful behaviour of garter snakes

Behavioral Modification as a Means of Reducing the Cost of Reproduction

Because relative clutch mass (RCM) adversely affects locomotor performance, and therefore presumably the survival rate of pregnant females, it is assumed to be constrained by natural selection. I propose that changes in antipredator tactics during pregnancy can reduce females' dependence on locomotion, thereby alleviating selection acting on RCM. Such a behavioral shift would be a more likely response to selection against poor locomotor ability because reductions in RCM have obvious disadvantages (i.e., decreasing fecundity) and can only partially improve speed and endurance. Comparisons of the locomotor performance and antipredator behaviors of pregnant female garter snakes (Thamnophis ordinoides) before and after parturition indicate that locomotor ability declines and that antipredator tactics change during gestation. Females tend more toward cryptic behavior during pregnancy than after. These observations are consistent with behavioral shifts observed in lizards during periods of reduced locomotor ability.

Incubation temperature has long-term effects on behaviour of young Pine snakes (Pituophis melanoleucus)

Eggs of pine snakes (Pituophis melanoleucus) were incubated at constant temperatures of 21°, 23°, 26°, 28°, 30° and 32° C to determine behavioural differences as a function of incubation temperature. For all behavioural and physiological measures hatchlings from medium incubation temperatures (26°, 28°) performed tests better than those hatchlings from eggs incubated at low temperatures (21°, 23°). For some behavioural tests hatchlings from eggs incubated at high temperature (30°, 32°) performed less well than medium temperature hatchlings. These differences were not due to ambient temperatures or age of testing since these were held constant. Some of the behavioural differences persisted for 24 weeks.

Role of the Pineal Gland in the Control of Annual Reproductive Behavioral and Physiological Cycles in the Red-Sided Garter Snake (Thamnophis sirtalis parietalis)

Red-sided garter snakes (Thamnophis sirtalis parietalis) exhibit a dissociated re productive pattern in nature: Male snakes court and mate with females after emergence from hibernation, when the gonads are regressed and not producing gametes or sex steroid hor mones. The proximate environmental cues used for timing this behavior appear to be the onset of warm ambient temperatures after prolonged exposure to cold temperatures. Pinealectomy blocks the normal onset of vernal courtship behavior in red-sided garter snakes. In the present study, snakes captured in the spring or the fall were pinealectomized in different seasons (i.e., spring or fall) prior to the onset of hibernation. Upon emergence, only 1 of 36 sham-operated animals failed to exhibit courtship behavior; 4 of 29 pinealectomized animals exhibited some courtship behavior, but none reached criterion. No animals courted 18 weeks after emer gence, and plasma testosterone levels were similar in pinealectomized and sham-operated animals, indicating that pinealectomy did not simply rephase courtship behavior in these snakes. Although some animals lost mass while others gained mass over the course of the study, this variable does not account for the absence of mating behavior in pinealectomized garter snakes. These data lend additional support to the hypothesis that the pineal gland directly influences reproductive behavior in the red-sided garter snake.

Intraspecific Variation in Thermoregulation, Movements and Habitat Use by Australian Blacksnakes, Pseudechis porphyriacus (Elapidae)

Radiotelemetric studies of snake behavior often have been based on few animals, monitored in single study areas for short periods of time. A four-year study involving three widely separated study areas, in which 44 blacksnakes (Pseudechis porphyriacus) were radio-tracked for an average of 90 days each, revealed unexpectedly high variability in habitat use, activity levels, daily movements and activity ranges. Significant variation was documented among individual snakes, between sexes, among seasons, among years, and among study areas. The only characteristic that showed little variation was activity temperature range: active blacksnakes maintained body temperatures of 28 to 31?C over a variety of seasons, study areas, and ambient temperatures. This constancy was apparently achieved by varying behavioral characteristics, especially activity levels and times. Activity ranges varied from 0.02 ha to over 40 ha in different snakes, and were larger in males during the mating season. Reproductive activity declined or ceased in two populations during a severe drought. The behavioral flexibility exhibited by P. porphyriacus makes it difficult to describe typical behavior for this species, and suggests that many previous radiotelemetric field studies of snakes should be inter- preted with caution.

Role of light and temperature in the regulation of reproduction in the red-sided garter snake, Thamnophis sirtalis parietalis

The influence of photoperiodic manipulation on sexual behavior and ovarian recrudescence of male and female red-sided garter snakes (Thamnophis sirtalis parietalis) was examined over a 4-year period. Snakes were exposed to photoperiodic manipulations before, during, and after a 17-week cold temperature dormancy; sexual behavior of males and females and ovarian recrudescence were observed after emergence from cold temperature dormancy. In the 1st year (1982), males were exposed to two conditions representing minimum and maximum exposure to daylight: (i) 6 weeks of a short-day prehibernation period (10L:14D, 28:18 °C), followed by 17 weeks of hibernation in complete darkness (0L:24D, 4 °C) and emergence into warm dark conditions (0L:24D, 28:18 °C); and (ii) 6 weeks of a long-day prehibernation period (14L:10D, 28:18 °C), followed by 17 weeks of hibernation with exposure to light (12L:12D, 4 °C) and emergence into warm, long days (14L:10D, 28:18 °C). Males in both conditions exhibited intense courtship behavior on emergence from hibernation. Females in 1982 were significantly influenced only by long-day prehibernation conditions (14L:10D, 28:18 °C); under these conditions, ovarian recrudescence on emergence was inhibited. Long prehibernation photoperiod did not significantly influence female receptive behavior on emergence, indicating that neuroendocrine control of ovarian activation and sexual behavior may be separate in this species. In three subsequent years (1983, 1984, 1985) none of the photoperiodic conditions significantly influenced male or female sexual behavior or ovarian recrudescence. Slight differences in experimental protocol in these subsequent years that may account for differences in results from 1982 are discussed. Finally, ovarian development was found to be clearly tied to the duration of cold temperature dormancy in this species. Females receiving 7 or 17 weeks of exposure to cold (4 °C) underwent vitellogenesis at similar frequencies. Most females receiving 0 or only 4 weeks of exposure to cold (4 °C) did not become vitellogenic. Mating on emergence was not a requirement for the initiation of vitellogenesis in this study.

Facilitation of courtship behavior in the male red-sided garter snake ( Thamnophis sirtalis parietalis) following lesions of the septum or nucleus sphericus

Courtship behavior in male red-sided garter snakes is limited to the period immediately following spring emergence. Lesions of the septum or nucleus sphericus prior to hibernation facilitate courtship behavior upon emergence the following spring. These lesions also had a significant effect on the reproductive physiology of the male snake. Snakes with lesions in the nucleus sphericus had a significantly higher concentration of circulating androgens compared to the control group. While animals with lesions in the septum exhibited elevated levels of circulating androgens, they were not statistically elevated when compared to the control group. The quantity of sexual granules in the epithelium of the renal sexual segment, a secondary sexual characteristic of male squamate reptiles, was significantly greater in lesioned animals. These results are the first to demonstrate a central inhibitory control of sexual behavior in a snake.

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

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

Pinealectomy blocks vernal courtship behavior in red-sided garter snakes

Male red-sided garter smakes (Thamnophis sirtalis parietalis) court only on emergence from winter dormancy. The salient proximate factor responsible for the initiation of courtship behavior appears to be warm ambient temperatures subsequent to sustained exposure to cold temperatures. In the present study, autumn-captured garter snakes were pinealectomized or sham-pinealectomized 1–2 weeks prior to hibernation. After 17 weeks of maintenance in several ambient lighting and temperature conditions, all males were tested for the presence of courtship behavior. No pinealectomized animals exhibited any indications of reproductive behavior, whereas 53% of sham-pinealectomized males actively courted females. Photoperiod did not influence the prevalence of mating behavior. These results suggest that the pineal gland mediates non-photoperiodic seasonal information in the garter snake. This is the first demonstration, in any vertebrate species, that the pineal gland can directly influence reproductive behavior.

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 < .001) more strikes at both moving and nonmoving stimuli when tested 4 hr after feeding, but the number of snakes fleeing from the stimuli was not affected.

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 three species was conducted in the laboratory. In Experiment 1, 241 one-day old snakes, roughly equally divided among the three species, were tested for defensive behaviors directed towards a moving or nonmoving stimulus. Thamnophis melanogaster babies were by far the most reactive in terms of strikes, bites, and defensive tongue-flicks. Thamnophis sirtalis and Thamnophis butleri were far less reactive and not significantly different from each other. In Experiment 2, adult females of each species reacted in ways similar to the neonates with the exception that the T. sirtalis females were more reactive towards the moving stimulus than were the T. butleri females. Experiment 3 showed large and significant differences in openfield behavior among the three species, but few significant correlations between open-field measures and antipredator responses. Although neonates in altricial species typically rely on adults for defense against predators, members of precocial species with no parental care must be ready to cope with potential predators soon after birth, which has consequences for subsequent behavioral development (cf. Burghardt, 1984). Snakes are among the most precocial of terrestrial vertebrates and are capable of engaging in defensive responses from the moment they are born, sometimes even before totally emerged from the egg in oviparous species (Burghardt, 1978). Because snakes exhibit a variety of defensive behaviors, they are excellent subjects for the comparative study of antipredator displays in closely related species prior to any effects of postnatal experience. This approach has been used successfully to examine innate differences in response to chemical cues from prey among closely related species of snakes (e.g., Burghardt, 1969) but has not previously been systematically extended to the study of neonatal antipredator behaviors. Although there are many anecdotal reports of defensive behavior in snakes (Greene, in press), few investigators have attempted to apply quantitative techniques to the study of

Effects of early sex steroid hormone treatment on courtship behavior and sexual attractivity in the red-sided garter snake, Thamnophis sirtalis parietalis

Previous research has shown that exogenous androgen fails to elicit courtship (chin-rubbing) behavior in adult male or female red-sided garter snakes (Thamnophis sirtalis parietalis). However, gonadectomized and intact newborn male and female red-sided garter snakes given silastic capsules containing testosterone exhibit chin-rubbing behavior; gonadectomized and untreated animals do not show this behavior. Both males and females also exhibit chin-rubbing behavior when treated with testosterone as yearlings. Hibernation stimulates chin-rubbing behavior only in males that have received androgen treatment as a neonate or as a yearling. Previous research has also shown that adult females, but not adult males, are courted if given estrogen treatment. Both newborn males and females will elicit chin-rubbing behavior from adult males if given estrogen treatment, indicating production and release of an attractiveness pheromone characteristic of adult females. Male red-sided garter snake breed for the first time on emergence from their second hibernation, whereas females probably do not breed until their third year of life. These data suggest that in the red-sided garter snake, a species that exhibits a dissociated reproductive tactic, sex steroid hormones act to organize central nervous system mechanisms subserving courtship behavior such that temperature, and not hormonal, fluctuations activate sexual behavior in the adult organism.

A Format for the Study of Envenomation Therapies

A necessary step in a comprehensive assessment of indigenous envenomation therapies is a framework in which seemingly disparate and fragmentary data may be grouped for comparison and analysis. In this paper data gathered in Belize in 1979-1982 is presented under topic headings which suggest parameters and problems that should be considered in a cross-cultural study of snakebite treatments. Accurate information is needed on the social history of patients, snake doctors, and others who might influence the course of treatment; beliefs about snake types and snake behavior; the circumstances of envenomation; facilities available for treatment; the stages of treatment; the components of medicines as well as their preparation and application in treatment.