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High-latitude environments are challenging for terrestrial ectotherms because short and cool active seasons generally limit the time available for foraging and growth, thereby negatively influencing life-history variables such as growth rate and age at maturity and ultimately, via fitness differences, their evolution. Many species show latitudinal clines in life-history traits, including growth rate and body size. We estimated growth curves of Plains Garter Snakes (Thamnophis radix (Baird and Girard, 1853)) near the northern limit of the species' range in central Alberta and compared our findings to similar estimates for more southerly populations. Despite a short growing season, female T radix at Miquelon Lake grew rapidly, reaching maturity in 1 or 2 years, similar to southern populations, and attained greater maximum sizes than snakes in southern populations. Overall, growth in this high-latitude population is comparable with what is seen in other conspecific populations. Possible reasons for lack of marked latitudinal effect include longer days at high latitudes, highly productive aquatic habitats for foraging, effective thermoregulation, reduced competition, and (or) countergradient variation in growth rate. Key words: ecology, ectotherm, Reptilia, growth, maturity, Plains Garter Snake, Thamnophis radix, high latitude, life history. Les milieux de haute latitude presentent d'importants defis pour les ectothermes terrestres parce que la brevite et la fraicheur des periodes actives limitent le temps dont ils disposent pour la quete de nourriture et la croissance, ce qui a une incidence negative sur des variables du cycle biologique comme le taux de croissance, l'age a la maturite et, a terme, par le biais de differences de valeur adaptative, revolution. Des caracteristiques du cycle biologique de nombreuses especes, dont le taux de croissance et la taille du corps, presentent des gradients latitudinaux. Nous avons estime les courbes de croissance de couleuvres des Plaines (Thamnophis radix (Baird et Girard, 1853)) pres de la limite septentrionale de l'aire de repartition de l'espece dans le centre de l'Alberta et compare nos resultats a des estimations semblables pour des populations plus meridionales. Malgre la brevite de la periode de croissance, les femelles T radix au lac Miquelon presentent une croissance rapide, arrivant a maturite en un an ou deux, a l'instar des populations meridionales, et atteignent des tailles maximums plus importantes que celles des couleuvres des populations meridionales. Dans l'ensemble, la croissance dans cette population de haute latitude est semblable a celle d' autres populations conspecifiques. Parmi les raisons pouvant eventuellement expliquer l'absence d'effet latitudinal marque figurent la longueur du jour a haute latitude, des habitats aquatiques tres productifs sur le plan de la quete de nourriture, une thermoregulation efficace, une plus faible concurrence et (ou) une variation contre-gradient du taux de croissance. Mots-cles : ecologie, ectotherme, reptiles, croissance, maturite, couleuvre des Plaines, Thamnophis radix, haute latitude, cycle biologique. [Traduit par la Redaction], Introduction Environmental heterogeneity, both spatial and temporal, is a potent evolutionary force that plays a key role in shaping the ecology of organisms (Levins 1968). Seasonality is a form of [...]

Death feigning, a variant of tonic immobility, is usually interpreted as a last-resort antipredator measure. The authors describe death feigning in grass snakes (Natrix natrix) and test some of its potential correlates. Death feigning was seen in 66% of wild-caught snakes but was not seen in hatchlings from laboratory-incubated eggs. Minimal indication of death feigning was mouth gaping, often with the tongue hanging free, but more dramatic cases involved voluntary supination and/or lack of muscle tone. Aside from hatchlings, which did not feign death, there was little variation in frequency or intensity of death feigning with body size. There was no effect of body temperature on death feigning nor were snakes that were moving when caught less likely to feign death than those that were not moving. Interpretation of the adaptive value of death feigning in grass snakes or in other animals is hampered by lack of evidence of this behavior in the field in response to natural predators. Keywords: snakes, death feigning, tonic immobility, antipredator behavior

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. Keywords: snakes, tonic immobility, antipredator behavior, supination

Abstract: Introduced species represent one of the greatest potential threats to persistence of native species. Therefore, it is important to understand the ecology of introduced species in order to develop [...]

Garter snakes were investigated to determine how resources are allocated to present and future reproduction and to various steps of reproduction. Results indicated that feeding during late pregnancy affects postpartum weight of the mother but not the weight of the offspring there were tradeoffs between postpartum weight and litter weight in spite of individual variations in body size and food intake and snakes appear to be well suited to tests on general issues such as those investigated in this study.

The common garter snake, Thamnophis sirtalis, ranges farther N than any other North American reptile. We examined the reproductive ecology of this species near its extreme northern limit in Wood Buffalo National Park (WBNP, 59 degrees 49'N, 112 degrees W, Northwest Territories, Canada). Our data suggest that individual females in this population rarely gave birth in 2 successive yr. Parturition normally occurred away from the den, in summer habitat, with the females subsequently migrating back to the hibernaculum. These life cycle features were similar to those reported for another northern population in Manitoba (50 degrees 30'N, 97 degrees 53'W) and may be a consequence of the climate and the distance between summer and winter habitat. However, there were important differences in the reproductive characteristics of WBNP and Manitoba populations. Most strikingly, female snakes at WBNP matured at large body sizes (greater than or equal to 570 mm SVL) than Manitoba snakes (greater than or equal to 527 mm SVL). Also, mean litter size for WBNP females was smaller than for Manitoba females (12.5 vs. 18.8 offspring/litter, respectively), but WBNP neonates were considerably larger than Manitoba neonates (191 vs. 154 mm SVL, respectively). Whether these differences between cold-climate populations of T. sirtalis are genetic or environmental in origin remains to be determined. Regardless, these two populations differ substantially in demography, indicating that there is no single suite of life history traits that characterizes northern T. sirtalis.