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Life-history traits of organisms are influenced by both genetic and environmental factors. We used counts of offspring in captive-born litters to determine how geographic location, year-to-year variation, and body size of mother affected litter size of Western Gartersnake (Thamnophis elegans) in four widely separated populations in British Columbia. Litter size varied significantly among populations, but that variation was largely explained by differences in maternal body size among populations; that is, larger females had larger litters. With maternal size treated as a covariate, there was no further significant effect of location or of different years within sites on litter size. The overall regression, pooled over sites and years, between litter size and size of mother accounted for 55% of the total variation in litter size. Nonetheless, the significant variation in body size among locations calls for explanation and the consequent differences in litter size could be important demographically. Presumably, the large amount of unexplained residual variation reflects other differences, beyond body size, between individual mothers. Such differences among individuals might be determined by genetics or by environmental effects such as foraging success, but our data cannot address this question. [ABSTRACT FROM AUTHOR]

Understanding habitat requirements of species is fundamental for their conservation and urban parks can provide key habitat for species in otherwise disturbed settings. Northwestern Gartersnakes (Thamnophis ordinoides) are common in parks in Saanich, British Columbia, but their specific habitat requirements are poorly understood. Based on previous studies and thermoregulatory needs of snakes, we predicted that edges, particularly field margins, would be heavily used by active snakes. We therefore used surveys that focused on edges to find snakes and measured edge-habitat use by comparing habitat variables at locations where snakes were found to the same variables at nearby random locations. habitat variables included composition and structure of vegetation, substrate temperature, aspect, and slope. overall, litter depth, canopy cover, a lack of bare ground and woody vegetation were the most important habitat variables for determining where snakes were found. our results provide a preliminary assessment to improve our understanding of habitat use for this species. the abundance of snakes found while surveying edges supports our initial assumption that edges are important habitat features but more work is required using multiple survey methods to further test this hypothesis. [ABSTRACT FROM AUTHOR]

Do high-latitude environments constrain life histories of ectotherms? One expectation is that shorter and cooler active seasons at high latitudes limit opportunities for maintenance of optimum body temperature and restrict time for foraging and therefore for growth and reproduction. Thus, under this hypothesis, individuals in high-latitude populations of wide-ranging species would be predicted to grow more slowly, have lower reproductive output, and perhaps reproduce less frequently than lower-latitude conspecifics. However, at Miquelon Lake in central Alberta, the Plains Garter Snake ( Thamnophis radix) grows as fast annually as more southerly conspecifics and reaches sexual maturity at the same age. Here, we make a comparable test of latitudinal variation in reproductive traits. Both litter size and offspring size were larger in the Miquelon Lake population than at lower latitudes. Moreover, female snakes could reproduce annually, although the frequency of annual reproduction remains unknown. Litter size was positively related to female size, but also varied annually, apparently in relation to the previous year's weather (higher litter size with lower rainfall and higher temperature the previous year); the most parsimonious interpretation of this observation is that warm, sunny weather facilitates the acquisition of capital resources for the subsequent year's reproduction. Overall, the Miquelon Lake snakes appear to have a 'fast' life history, presumably as a result of a productive environment that provides an abundance of anurans, which constitute the primary prey of T. radix at this site, but this hypothesis is untested. [ABSTRACT FROM AUTHOR]

Colours influence numerous aspects of an animal's ecology. One possibility is that colour helps make an animal cryptic against the background on which it is resting. We test this hypothesis for two different, geographically separated colour forms (dark forms and light forms) of the Western Terrestrial Garter Snake, Thamnophis elegans. We quantified crypsis of snakes, in terms of colour (chromatic crypsis) and brightness (achromatic crypsis), by using objective measures of spectral reflectance of snakes and the surrounding habitat. These data were visually modelled from the perspective of potential snake predators and human researchers. Overall, snakes of both colour forms selected basking sites that increased chromatic crypsis over that which would have been achievable on random backgrounds. Both colour forms of T. elegans appear to exhibit similar achromatic and chromatic crypsis when viewed by potential predators, such as mammals and birds. From the perspective of the human visual model, dark T. elegans were generally more chromatically cryptic than light T. elegans, contrary to our a priori subjective impression. The main contribution of the present study is that we provide one of the first objective comparisons of snakes and their backgrounds as a measure of crypsis. Although we found some evidence for crypsis as a factor in choice of basking sites for snakes, other factors (e.g. thermoregulatory opportunities) undoubtedly play important roles as well. We also have not addressed whether snakes involved in other activities are cryptic or whether there are differences between the sexes or between reproductive and nonreproductive females. The adaptive significance of colour variation has been studied in diverse taxonomic groups. Although the mechanisms are not straightforward, the opportunities to carry out further work in this area are enhanced by the availability of objective approaches. © 2013 The Linnean Society of London [ABSTRACT FROM AUTHOR]

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The North American genus Thamnophis is a widely distributed and abundant group of snakes. Previous research has indicated that most garter snakes are generalist predators that largely consume anurans, with some degree of geographic and temporal plasticity in response to resource variation. We studied the dietary habits of the Plains Garter Snake, Thamnophis radix, based on stomach contents from 548 animals collected in the field from 1995-2006 at the northern limit of the species' range in central Alberta, Canada. Feeding frequency overall was low (22%) and was highest in spring and early summer. Diet was composed mainly of anurans (85%), especially. Wood Frogs (Rana sylvatica) and Boreal Chorus Frogs (Pseudacris maculata), and occasionally invertebrates (10%) and small mammals (5%). Small snakes (<200 mm) began feeding shortly after birth and consumed mainly smaller frogs. Larger snakes ate a wider range of prey sizes and types, but frogs still constituted the majority of prey consumed. Despite sexual size dimorphism, males and females ate prey of the same size and type; however, gravid females contained food less frequently than both males and nongravid females. This study adds to the growing number of dietary studies on T. radix and provides additional evidence for the ecological plasticity of Thamnophis species. Further studies are needed to examine how important these snakes are as components of wetland food chains. [ABSTRACT FROM AUTHOR]

Presents research on the reproductive traits and the influence of food intake in Thamnophis elegans, garter snakes. Examination of life-history theory; Distinctions in life-history theory; Experiments undertaken in this research; Statistical data analysis; Results of this research.

The common garter snake, Thamnophis sirtalis, has frequently been studied, but never in the far north where climatic influences on distribution and abundance might be expected to be severe. We examined the structure and dynamics of a communal den population at the northern limit of the species' range. Snakes were sampled at the hibernaculum from spring 1983 to spring 1987. Males were more easily caught than females, and few inferences could be made about the latter. Population estimates, though possessing wide standard errors, seemed to indicate that the denning population of 500-600 snakes, mostly adults, was stable. Annual survivorship of large males (≥400 mm SVL) was high (0.68-0.98) and was not correlated with body size. Thirty-four snakes that were first marked in 1983 were recaptured in the spring of 1987, indicating that they had survived at least six years, assuming they were a minimum of two years old when first marked. Recruitment to the denning population consisted of an influx of 'new' individuals (450-550 mm SVL) each autumn. It is not known where these snakes spend the first few years of their existence. The relative Stability of numbers and high overwinter survivorship observed over the course of this study contrast sharply with the only previous study of T. sirtalis in cold climates. [ABSTRACT FROM AUTHOR]