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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 [...]

The article informs that Northern Pacific Rattlesnake, Crotalus oreganus, has long been thought of as an asocial animal. However, recent research reveals that snakes engage in a variety of social interactions, including mate-guarding behavior. On a visit to a site in southern British Columbia, Canada, researchers observed a large freshly molted rattlesnake coiled on top of a smaller snake that appeared to be shedding its skin.

The article studies the natural history of milksnake or Lampropeltis triangulum along Sixteen Mile Creek in Oakville, Ontario. Topics covered include the maximum body size of milksnakes in southern Ontario, the feeding habits of hatchling Milksnakes in captivity, and the evidence of sexual dimorphism in size and relative mass.

Generalist species are often both widely distributed and abundant. They also are often plastic in their ecology, both spatially and temporally, in response to variation in resources. Here, we study the food habits of the widespread European Grass Snake, Natrix natrix, in Kent in southeastern England. As elsewhere in their range, Grass Snakes at our study site mainly ate anurans (63%); however, small mammals also were fairly common in the diet (25%) and fish (10%) and birds (1%) were taken occasionally. About 65% of prey eaten by snakes were swallowed headfirst, but orientation of prey during ingestion varied among prey types. Although anurans are the major prey of Grass Snakes, the predominant species in their diet varies geographically, presumably in relation to availability; at our site, the most frequently eaten species (63%) was the introduced Marsh Frog, Rana ridibunda, which is very common and possibly influences abundance of snakes. We obtained few data on feeding habits of small snakes (< 400 nun SVL) but found anuran prey in the smallest snake in our sample; other prey types were eaten by larger snakes and therefore presumably are added to the diet as snakes grow. Maximum size of prey increased with snake size, but large snakes nonetheless continued to eat small prey as well. However, because Grass Snakes are sexually dimorphic (females larger), such size effects may be confounded with sex effects. Snakes had food in their stomachs less frequently in midsummer than they did in early and late summer. Nonetheless, even after adjusting for such seasonal variation, gravid females contained food less frequently than nongravid females. Thus, gravid females of this oviparous species apparently exhibit an anorexia similar to that seen in pregnant females of many viviparous species. [ABSTRACT FROM AUTHOR]