Thamnophis Elegans Research Articles

Observations of Tooth Surface Morphology in Snakes

ABSTRACr.-An investigation of tooth surface features in a number of snake taxa revealed that, in addition to the typical lateral and medial some species possess accessory ridges that are generally confined to the posterior tooth surface and are most pronounced at the tooth base. The presence of accessory ridges appears to be confined to species with relatively long teeth that are piscivorous or feed on soft-bodied invertebrates. Several hypotheses are presented regarding the functional significance of these features. Investigations of morphology in snakes have concentrated primarily upon modifications associated with the delivery of venom (Anthony, 1955; Bogert, 1943; Brattstrom, 1964; Klauber, 1939; Smith, 1952). General treatments of snake and other reptilian dentition can be found in Edmund (1969) and Peyer (1968). Detailed descriptions and functional considerations of the surface features on typical noncanaliculate teeth have been confined to the position and extent of the or ridges. Frazzetta (1966) described the ridges on the teeth of several species of Python. These paired or cutting edges as he referred to them, run parallel to each other from the apex of the tooth; one extends laterally along the tooth shaft, the other medially. Wright et al. (1979) employed scanning electron microscopy to examine these dental ridges, as well as other aspects of the morphology, in the colubrid species Thamnophis elegans. Except for the 2 or 3 rear maxillary teeth, the orientation of the ridges is the same as that described for the pythons. The relative lengths of the ridges depend upon the tooth type and location. On the enlarged rear maxillary teeth the orientation of the ridges is shifted approximately 90? to form a long, bladelike posterior ridge and short anterior ridge. Descriptions of unique tooth morphology in which ridges are mentioned or figured have been reported for Xenodermus (Bogert, 1964), Iguanognathus (Boulenger, 1898), Dinodon and Stegonotus (McDowell, 1972), Regina (Rossman, 1963), Scaphiodontophis (Taylor and Smith, 1943), and Xenopeltis

The Thermal Dependence of Locomotion, Tongue Flicking, Digestion, and Oxygen Consumption in the Wandering Garter Snake

The body temperature (Tb) of garter snakes (Thamnophis elegans) can vary considerably in the course of a day (e.g., 4-33 C), and information on how Tb affects physiological and behavioral processes is required to evaluate the significance of that variation. We measured crawling speed, swimming speed, tongue-flicking rate, digestive rate, and oxygen consumption at Tb's of 5-35 C in snakes collected in eastern Washington and acclimated to September field photoperiod and temperature cycles. All functions were strongly dependent on Tb. The maximum speed of crawling (X̄ = 0.74 m s−1) occurred at Tb = 34.5 C; that of swimming (X̄ = 0.69 m s−1) occurred at Tb = 28.5. At < 30 C, the snakes crawled more slowly than they swam, but the reverse was true at higher Tb. At Tb = 30 C, the snakes moved their tongues up and down at a maximum rate of 22 Hz. Digestion rate increased sharply above 20 C, to a maximum of 0.45 mice/day within the Tb range of 25-35 C. All snakes regurgitated their meal at 10 C. The Q10 values for mass-specific oxygen consumption over the 5-15, 15-25, and 25-35 C Tb ranges were 2.4, 1.3, and 5.0, respectively. Among the performances studied, swimming speed was the least sensitive, and digestion rate the most sensitive, to Tb. FieldTb data indicate that all functions would be near maximum levels during the day but would be significantly reduced at night. We conclude that no single Tb is best for the ecological tasks of prey capture, predator avoidance, and energy conservation.

Behavioural variation in natural populations. IV. mendelian models and heritability of a feeding response in the garter snake, Thamnophis elegans

Heritability of a feeding response was very similar in two conspecific populations despite divergence in average behaviour. These results support the view that genetic variances evolve more slowly than phenotypic means. One locus models with absolute penetrance gave poor fits to family data from both populations.

Predation of White-Crowned Sparrow Nestlings by the Western Terrestrial Garter Snake in San francisco, California

Predation of White-Crowned Sparrow Nestlings by the Western Terrestrial Garter Snake in San francisco, California

Geographic variation in the foraging behavior of the garter snake, Thamnophis elegans

Behavioral comparisons were made of two populations of the garter snake Thamnophis elegans: a typical population with semi-aquatic habits and diet (inland population), and a coastal population that has entered a terrestrial feeding niche. Laboratory-born snakes of both populations were compared for their tendency to eat fish and their aquatic foraging behavior.

Diurnal ventilatory patterns in the garter snake,Thamnophis elegans

Garter snakes,Thamnophis elegans, were entrained to a 14L (06.30–20.30 h) 10D (20.30–06.30 h) cycle for five weeks at 25 °C. Following entrainment, simultaneous measurements of ventilation and oxygen uptake were made. Pulmonary oxygen uptake ( $$\dot V_{O_2 } $$ ) exhibited a diurnal rhythm with minimum values of $$\dot V_{O_2 } $$ occurring during 10D. The diurnal rhythm persisted during continuous darkness (24D) and was considered to be endogenous. Minute ventilation ( $$\dot VE$$ ) decreased during 10D. The decrease in $$\dot VE$$ persisted during 24D. Diurnal alterations in $$\dot VE$$ were attributed to a change in breathing frequency (f). The decrease inf during 10D was postulated to be characteristic of a ‘sleeping’ state. The decrease in $$\dot VE$$ of the ‘sleeping’ state was of a greater magnitude than that for $$\dot V_{O_2 } $$ . Consequently, a pronounced diurnal rhythm in air convection requirement $$(\dot VE/\dot V_{O_2 } )$$ resulted. The data suggest that the regulatory mechanisms of the ‘sleeping’ state differ from that of the ‘waking’ state.

Responses to Ophiophagous Snakes by Snakes of the Genus Thamnophis

Naive garter snakes, Thamnophis (Colubridae), were tested for responses to skin chemicals from ophiophagous snakes. Thamnophis elegans emitted a significantly greater number of tongue flicks to swabs rubbed against the skin of the kingsnake Lampropeltis getulus, an ophiophagous species, than to those from some generally nonophiophagous snakes or to blank swabs. Thamnophis sirtalis emitted more tongue flicks to swabs from the black racer Coluber constrictor, another ophiophage, than to control-snake or blank swabs. Olfactometric studies show that T. sirtalis is sensitive to airborne chemical cues from Lampropeltis, emitting more tongue flicks to the scent of this snake than to the scent of the rat snake Elaphe obsoleta or to plain air. The results from this study suggest that some of the same snake species recognized as predators by crotaline snakes are recognized as such by Thamnophis.

Garter Snake Diets in a Fluctuating Environment: A Seven‐Year Study

Diets of the terrestrial garter snake (Thamnophis elegans) and the common garter snake (T. sirtalis) were studied during seven consecutive summers at a lake in northern California, USA. The snakes were opportunities feeders; their diets varied dramatically from year to year, parallel with the abundance of prey. Snakes foraged more successfully, judging from the incidence of stomachs containing prey, in years when metamorphic toads (Bufo boreas) were available. Breeding failure in toads with associated with lowering lake level.

A Quantitative Approach to Antipredator Performance: Salamander Defense against Snake Attack

A factorial experiment was used to evaluate the antipredator performance of salamanders (Plethodon cinereus) attacked by garter snakes (Thamnophis elegans). Large salamander size, antipredator behavior and the presence of a tail each produced a significant delay in ingestion rate. These three components of the salamander defense system showed simple additive interactions when antipredator performance was measured on a logarithmic scale. When performance was measured on an arithmetic scale, these three components showed multiplicative effects or synergisms.

A Biophysical Analysis of Daily and Seasonal Utilization of Climate Space by a Montane Snake

A model of the energy budget for the wandering garter snake (Thamnophis elegans vagrans) was constructed from equations describing heat flows at the animal's skin surface and body core. A new method was developed for expressing the role of heat transfer from the substrate in influencing body temperature. Convection coefficients were evaluated on live snakes in a wind tunnel and determined to be essentially identical to those for cylinders. Climate space diagrams were generated from energy budget equations for snakes in their natural montane habitats at 2600 m in Larimer County, Colorado. The attainable body temperatures revealed by climate space diagrams show that the physical environments normally encountered by T. elegans are surprisingly harsh. For example, in July the maximum voluntary body temperature (35°C) would be exceeded in open microhabitats (bare ground, rocks, grass) for °5.5—6 h of each clear day. Optimum body temperatures (26—32°C) could be attained for only °1.5—2.5 h each day, and the critical thermal maximum would be exceeded for at least 3 h in bare—ground or rock microhabitats. On cool or cloudy days in May and September, a snake could barely attain the minimum optimum body temperature in any microhabitat.

Anaerobic metabolism and behavior during predatory encounters between snakes (Thamnophis elegans) and salamanders (Plethodon jordani).

1. We staged predatory encounters between snakes and salamanders in the laboratory. 2. Both snakes and salamanders accumulated significant quantities of lactic acid (0.3-2.3 mg/g) during predatory encounters. In a typical 14.4 min encounter, lactate concentration reached 260% of resting levels in snake predators and 880% of resting levels in salamander prey. This is one of the first demonstrations of anaerobiosis during natural 'burst' activity in both predator and prey. 3. Salamander responses to snake attack were surprisingly variable, and included writhing, thrashing, tail wrapping, tail autotomy, and biting. Antipredator responses were effective in nearly one third of trials. Lactate concentration was significantly correlated with duration of predatory encounters (r=0.57), snake mass, and salamander mass (Table 3). 4. Our calculations suggest that attack and ingestion of prey may cost snakes less than 1% of energy assimilated from prey.

Microgeographic variation in the diets of garter snakes.

Diets of the terrestrial garter snake (Thamnophis elegans) and the common garter snake (T. sirtalis) were studied at 22 sites in an area of about 250 km2 in northern California, during the summers of 1978-80. Overall, T. sirtalis consumed mostly amphibian and T. elegans ate an equal mixture of amphibians, fish, and leeches. However, this was more an effect of differential distribution of the two species among sites than of habitat partitioning within sites. Site was 5 times better as a predictor of diet than was species of snake. The relative frequency of T. sirtalis at the sites was correlated with the number of amphibian species.

Effects of progesterone and estrogen on the histology of the oviduct of the garter snake, Thamnophis elegans

Silastic capsules packed with estradiol and/or progesterone were implanted in ovariectomized viviparous garter snakes ( Thamnophis elegans) in order to define the role of these steroids in inducing histological recrudescence in the uterine segment of the oviduct. During the preovulatory period, the uterine tubuloalveolar glands and tall columnar, luminal epithelium of intact snakes were exceedingly well-developed and possessed numerous PAS-positive granules. Plasma estrogen concentrations were quite high (1833 ± 167 pg/ml) at this time and progesterone levels were variable (3.3 ± 2.3 ng/ml). Ovariectomy significantly reduced plasma levels of estrogen (79 ± 48 pg) and progesterone (1.1 ± 0.3 ng/ml) as well as the height and secretory condition of the luminal and glandular epithelium of the uterus. Administration of estradiol to ovariectomized garter snakes for 10 days elevated plasma estrogen levels to 758 ± 351 pg/ml and partially restored epithelial cell height and glandular activity. Administration of progesterone elevated plasma levels to physiological concentrations (4.3 ± 2.6 ng/ml) but had little or no stimulatory effect on uterine histology. Simultaneous administration of estradiol and progesterone for 10 days failed to induce additional stimulatory effects on uterine histology over and above those produced by estradiol alone. Results of this study indicate that estradiol is the most important ovarian hormone in regulating development of the uterus. However, additional hormones, other than progesterone, may possibly be required for full restoration of the garter snake uterus to the preovulatory condition.

Differential Susceptibility of Sympatric Garter Snake Species to Amphibian Skin Secretions

On Vancouver Island, the garter snake Thamnophis sirtalis preys heavily on amphibians while two sympatric garter snake species do not. One possible explanation is that the species have different preferences for such prey and/or that they are differentially susceptible to noxious or toxic amphibian skin secretions. These ideas were examined in this study. Relative prey preferences (in terms of tongue flicks) did not differ significantly among naive young of the three species. Thamnophis elegans and T. sirtalis, however, showed overall higher tongue-flick responses than T. ordinoides to amphibian extracts. Also, T. sirtalis and T. elegans ate more amphibians in feeding experiments than T. ordinoides. Neither T. elegans or T. ordinoides suffered any apparent ill effects when force-fed whole Rana aurora, Bufo boreas and Hyla regilla, but both suffered apparent loss of motor function when force-fed whole Taricha granulosa. In general, Thamnophis sirtalis readily ate all amphibian species offered without any apparent ill effects and, when force-fed Taricha granulosa, a majority of snakes were unaffected by tarichatoxin. It appears that Taricha, while not lethal, may be sufficiently debilitating that it is avoided by Thamnophis elegans and T. ordinoides. Differential susceptibility to toxins in general, however, does not seem to explain the differential consumption of amphibians by these three species on Vancouver Island.

Behavioral Variation in Natural Populations. I. Phenotypic, Genetic and Environmental Correlations Between Chemoreceptive Responses to Prey in the Garter Snake, Thamnophis elegans

Behavioral Variation in Natural Populations. I. Phenotypic, Genetic and Environmental Correlations Between Chemoreceptive Responses to Prey in the Garter Snake, Thamnophis elegans

The toxic Duvernoy's secretion of the wandering garter snake, Thamnophis elegans vagrans

The Duvernoy's secretion of the wandering garter snake ( Thamnophis elegans vagrans) is highly toxic to mice, causing marked hemorrhaging in the lungs, diaphragm, mesentery and stomach lining, as well as mild local hemorrhaging. Systemic hemorrhaging was most pronounced in mice receiving doses approximating the p. ld 50, while doses two times the ld 50 or greater produced massive hermorrhaging in the lungs and diaphragm only. Local extravasations were directly proportional to dose. Oral secretions other than Duvernoy's secretion failed to produce lethal effects in mice challenged with doses up to 7 times the ld 50 of Duvernoy's secretion. A micro-aspiration techniques for the collection of Duvernoy's secretion from colubrid snakes is described, and liquid as well as dried secretion yields for Thamnophis elegans vagrans are presented.

Remarks concerning Certain Western Garter Snakes of the Thamnophis elegans Complex

Thamnophis elegans biscutatus is a valid subspecies of the Klamath Lakes basin distinguishable from its nearest relatives by size, number of scale rows, head shape, and especially by habits and habitat. Thamnophis errans of the Sierra Madre Occidental in Mexico is a distinct species, though closely related to T. elegans vagrans, and perhaps to T. e. hueyi of Baja California. In attempting to prepare species-accounts of garter snakes for the Catalogue of American Amphibians and Reptiles sponsored by the Society for the Study of Amphibians and Reptiles, I have been puzzled and intrigued by several taxonomic problems that require clarification. My own original field studies and museum studies of Thamnophis were carried on mainly in the period 1933-1936. Obviously, in the period of almost half a century that has elapsed, garter snake classification has made notable progress, with new material, new methods and techniques and more intensive studies, all providing greater insight into the relationships within this complex group. However, some of the facts that were revealed from 15 to more than 40 years ago and that still have important bearing on classification, seem to have been overlooked or forgotten. Hence, I offer the present contribution without having much new data concerning the snakes themselves. The present report is concerned with two separate problems. The first concerns the validity of the subspecies Thamnophis elegans biscutatus endemic to the Klamath Lakes basin, and its relationships to the neighboring allopatric subspecies T. e. elegans, T. e. vagrans, and T. couchi hydrophilus. The second involves the status of the Mexican garter snake Thamnophis errans-whether it is a distinct species or intergrades with T. elegans vagrans of the southwestern United States. VALIDITY OF THAMNOPHIS ELEGANS BISCUTATUS

Effects of seasonal acclimation on the preferred body temperature of Thamnophis elegans vagrans

1. 1.|An Experimental group of wandering garter snakes from a montane habitat was maintained over winter under laboratory conditions of total darkness and 4°C. 2. 2.|Their mean preferred body temperature (30.7°C) on a constant temperature thermal gradient was significantly higher than the preferred body temperature (24.5°C) of another group of wandering garter snakes collected and tested in late summer.

Feeding habits and diet overlap of three species of garter snakes (Thamnophis) on Vancouver Island

Closely related, sympatrtc species of organisms often show resource partitioning. In this study, diet partitioning is examined in three sympalric species of garter snakes (Thamnophis) on Vancouver Island. Thamnophis sirtalis feeds mainly on amphibians and earthworms, Thamnophis ordinoides on earthworms and slugs, and Thamnophis elegans on slugs, fish, and small mammals. Thamnophis sirtalis and T. ordinoides, which are mote widely distributed on Vancouver Island than is T. elegans, have not been shown to modify their diets in the absence of T. elegans, but it is suggested that this lack of niche shift may be due to variations in prey availability. Neither innate differences in food preferences among the species nor interspecific competition for food have been shown to explain the observed differences in diet among the three species. Certain types of prey appear more likely than others to turn up in large numbers in stomach samples and it is suggested that this may be due to variations in ease of capture and (or) abundance. Possible explanations of the observed diets are discussed.

Polymorphism and Geographic Variation in the Feeding Behavior of the Garter Snake Thamnophis elegans

Geographic variation in behaviors that influence resource utilization is a key component in current ecological theory, but the phenomenon has been poorly documented. Propensity to attack slugs varies geographically in a western garter snake, Thamnophis elegans. Many naive, newborn snakes from inland localities in California refuse to eat slugs. In contrast, virtually all naive young from coastal localities eat slugs. There is, however, no demonstrable polymorphism or geographic variation for propensity to eat anurans. Both coastal and inland snakes consistently eat anurans.