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Abstract: Snakes often seek shelter under rocks or other physical cover objects, which provide protection from both predators and unfavourable weather and also may be used actively in thermoregulatory behaviour. Presumably, snakes are limited, by their own body size, to some minimum rock size, so that we should expect a positive relationship between a snake''s size and the size of the rock it uses. I tested this hypothesis for the watersnake, Nerodia sipedon, along a creek in a peri-urban setting in southern Ontario, Canada. Although larger snakes tended to be found under larger rocks, the relationship was weak. A composite measure of rock size from PCA was not markedly better than simple rock length. Sizes of rocks used by snakes did not change over the active season. Snakes tended to be found under the largest rock in their immediate vicinity, but distances from used rocks to equally big or bigger rocks rarely exceeded a few metres. Similarly, measurements of rocks on transects along the creek showed that, although small rocks predominated, all transects contained rocks large enough for snakes. Thus, it seems unlikely that cover is limited for watersnakes at this site. However, unmeasured factors such as temperature or other physical characters of rocks could change that conclusion. These factors would best be determined by manipulative experiments. [Copyright &y& Elsevier]

Tonic immobility is a common response of animals to capture by a predator; in some cases, the behaviour is elaborated into death-feigning. Death-feigning is usually interpreted as a last-resort anti-predator tactic that depends on the predator ceasing or slowing its attack when the prey is apparently dead, thus buying time for the prey to escape if the predator’s attention is directed elsewhere, even momentarily. I tested the effects of different handling regimes on the expression of death-feigning in the grass snake ( Natrix natrix). In one test, degree of handling had a significant effect on frequency of death-feigning in small snakes, with snakes that received more handling feigning death more often. A second test showed that different initial handling regimes also affected the probability of death-feigning in large snakes, with snakes initially held by the tail feigning death least frequently and those initially held by the head most frequently. Thus, increased apparent threat to a vulnerable part of the body is more likely to result in death-feigning. It remains to be seen whether death-feigning can reduce the threat posed by real predators, but immobility is frequently carried over into the post-release period, during which the animal presumably weighs its chances and awaits an opportunity to escape. Regardless of cause, death-feigning snakes exhibited significantly more frequent and longer post-release immobility than did non-death-feigning snakes, which typically fled immediately upon release. Overall, small snakes feigned death less frequently than adults and were more likely to flee upon release, suggesting that immobility is a riskier anti-predator defence strategy for them. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Sharp-tailed Snake, Contia tenuis, has a small and highly fragmented range in British Columbia, where it is considered endangered. Known sites are few in number and generally small in spatial extent; numbers of snakes apparently are correspondingly low. Furthermore, most known sites for the species are on private lands in areas that are fairly heavily developed or being developed. Thus, the species is under serious threat of habitat alteration or loss. Although land stewardship has been a valuable conservation tool in this case, we also need to identify the key habitat requirements of Sharp-tailed Snakes to identify potential new sites, modify former or potential ones, or even create new ones. In this study, we compared sites known to harbour Sharptailed Snakes with those that seemed subjectively similar and therefore potentially suitable. We also compared these known and potential sites with randomly chosen nearby locations. Variability of most measured features was high, both within and among site/location categories. Nonetheless, we found significant differences between known and potential sites and between those locations and random ones. Overall, locations known to be used by snakes had a more southerly aspect, more rock cover, shallower soil and litter, and less shrub cover than other sites. This study was constrained by the small number of known sites for Sharp-tailed Snakes in southwestern British Columbia, making our conclusions suggestive rather than definitive. Future work should incorporate additional variables. It also might be useful to undertake comparative habitat studies elsewhere in the range of the Sharp-tailed Snake where it is more common. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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]