Individual Snakes Research Articles

A time-calibrated phylogenetic approach to assessing the phylogeography, colonization history and phenotypic evolution of snakes in the Japanese Izu Islands

Aim We infer the biogeography and colonization history of a dispersal-limited terrestrial vertebrate, the Japanese four-lined ratsnake (Elaphe quadrivirgata), to reveal the number of times mainland populations have invaded the Izu Archipelago of Japan, the mainland sources of these colonists, and the time-scale of colonization. We compare these results with those of past studies in an attempt to uncover general biogeographical patterns. Moreover, we briefly examine the significance of colonization history when evaluating the evolution of body size and melanism of the Izu Island E. quadrivirgata populations. Location The Izu Islands (Oshima, Toshima, Niijima, Shikine, Kozu, Tadanae and Mikura), a volcanic archipelago off the Pacific coast of central Japan. Methods We obtained DNA sequences of the mitochondrial cytochrome b gene (1117 base pairs) from 373 individual snakes sampled from seven of the Izu Islands and 25 mainland localities. We employed partitioned Bayesian phylogenetic analyses assuming a relaxed molecular clock to estimate phylogenetic relationships among extant haplotypes and to give an explicit temporal scale to the timing of clade divergence, colonization history and tempo of body-size evolution. Moreover, we employed model-based biogeographical analysis to calculate the minimum number of times E. quadrivirgata colonized the Izu Islands. Results We found evidence that three separate regions of the Izu Archipelago have been colonized independently from mainland ancestors within the past 0.58–0.20 Ma. The Izu Peninsula plus Oshima and Mikura were both colonized independently from lineages inhabiting eastern mainland Japan. The Toshima, Niijima, Shikine, Kozu and Tadanae populations all derive from a single colonization from western mainland Japan. Oshima has been subject to three or possibly four colonizations. Main conclusions These results support the hypothesis that the extreme body-size disparity among island populations of this ratsnake evolved in situ. Moreover, the fact that the dwarf, melanistic population inhabiting Oshima descends from multiple mainland colonization events is evidence of an extremely strong natural selection pressure resulting in the rapid evolution of this unique morphology. These results contrast with theoretical predictions that natural selection pressures should play a decreased role on islands close to the mainland and/or subject to frequent or recent immigration.

Correlated geographic variation in predation risk and antipredator behaviour within a wide‐ranging snake species (Notechis scutatus, Elapidae)

AbstractGeographic variation in antipredator behaviour within wide‐ranging species may be driven by both genetic and environmental influences. We quantified antipredator responses in neonatal (laboratory born, n = 555) and adult (field caught, n = 346) tiger snakes (Notechis scutatus) from 11 mainland and island sites in southern Australia. We used these data to test predictions from Bonnet et al.'s hypothesis that the vigour of antipredator responses in this species reflects behavioural plasticity (in turn, driven by an individual snake's exposure to predators during its lifetime) rather than by genetic variation in this trait. We used the number of predator taxa in each area as an index of predator risk. As predicted, adult snakes from predator‐rich areas had more vigorous defensive responses when handled, whereas neonatal behaviour (although also variable among populations) was unrelated to predator species richness. Adult males bit more readily than adult females (as expected from the greater predation exposure of males during mate searching) but no such sex difference was evident in neonates. Although alternative models remain possible, our data are most consistent with the hypothesis that geographic divergence in antipredator tactics within this species primarily reflects developmentally plastic responses to local predation risk.

Purification and Functional Characterisation of Rhiminopeptidase A, a Novel Aminopeptidase from the Venom of Bitis gabonica rhinoceros

BackgroundSnake bite is a major neglected public health issue within poor communities living in the rural areas of several countries throughout the world. An estimated 2.5 million people are bitten by snakes each year and the cost and lack of efficacy of current anti-venom therapy, together with the lack of detailed knowledge about toxic components of venom and their modes of action, and the unavailability of treatments in rural areas mean that annually there are around 125,000 deaths worldwide. In order to develop cheaper and more effective therapeutics, the toxic components of snake venom and their modes of action need to be clearly understood. One particularly poorly understood component of snake venom is aminopeptidases. These are exo-metalloproteases, which, in mammals, are involved in important physiological functions such as the maintenance of blood pressure and brain function. Although aminopeptidase activities have been reported in some snake venoms, no detailed analysis of any individual snake venom aminopeptidases has been performed so far. As is the case for mammals, snake venom aminopeptidases may also play important roles in altering the physiological functions of victims during envenomation. In order to further understand this important group of snake venom enzymes we have isolated, functionally characterised and analysed the sequence-structure relationships of an aminopeptidase from the venom of the large, highly venomous West African gaboon viper, Bitis gabonica rhinoceros. Methodology and Principal Findings The venom of B. g. rhinoceros was fractionated by size exclusion chromatography and fractions with aminopeptidase activities were isolated. Fractions with aminopeptidase activities showed a pure protein with a molecular weight of 150 kDa on SDS-PAGE. In the absence of calcium, this purified protein had broad aminopeptidase activities against acidic, basic and neutral amino acids but in the presence of calcium, it had only acidic aminopeptidase activity (APA). Together with the functional data, mass spectrometry analysis of the purified protein confirmed this as an aminopeptidase A and thus this has been named as rhiminopeptidase A. The complete gene sequence of rhiminopeptidase A was obtained by sequencing the PCR amplified aminopeptidase A gene from the venom gland cDNA of B. g. rhinoceros. The gene codes for a predicted protein of 955 amino acids (110 kDa), which contains the key amino acids necessary for functioning as an aminopeptidase A. A structural model of rhiminopeptidase A shows the structure to consist of 4 domains: an N-terminal saddle-shaped β domain, a mixed α and β catalytic domain, a β-sandwich domain and a C-terminal α helical domain.ConclusionsThis study describes the discovery and characterisation of a novel aminopeptidase A from the venom of B. g. rhinoceros and highlights its potential biological importance. Similar to mammalian aminopeptidases, rhiminopeptidase A might be capable of playing roles in altering the blood pressure and brain function of victims. Furthermore, it could have additional effects on the biological functions of other host proteins by cleaving their N-terminal amino acids. This study points towards the importance of complete analysis of individual components of snake venom in order to develop effective therapies for snake bites.

Discordant patterns of population structure for two co‐distributed snake species across a fragmented Ontario landscape

AbstractAim The goal of our study was to investigate the effects of a fragmented landscape on the genetic population structure of two sympatric snake species that differ in habitat preference. The eastern garter snake (Thamnophis sirtalis sirtalis) is a common, habitat generalist, whereas the endangered eastern foxsnake (Mintonius [Elaphe] gloydi) is rarer, geographically restricted, and a marsh‐specialist. We were most interested in comparing the genetic population structure of both species and identifying any natural and human‐created features of the landscape that overlap with genetic disjunctions.Location Southwestern Ontario, Canada, surveying over half of the remaining range of the eastern foxsnake.Methods We utilized DNA microsatellite markers to examine genetic population structure of both species. The number of genetically distinct clusters for each species was determined using both Bayesian spatial assignment and spatial principal component analyses (sPCA). Genetic clusters were overlaid onto a habitat map to deduce possible physiognomic barriers to gene flow.Results Spatial assignment revealed three genetic clusters for garter snakes and five for foxsnakes. Each individual garter snake had a near equal probability of membership to two or more clusters with no cluster mapping onto a discrete geographic region, indicating that garter snakes comprise a single genetic population. The identified foxsnake clusters correspond to geographically circumscribed locations on the landscape, roughly coincident with isolated patches of suitable habitat. sPCAs revealed significant global allelic structure for foxsnakes, but not for garter snakes. No significant local structure was found for either species.Main Conclusions Our results imply that foxsnakes and garter snakes are differentially impacted by the same landscape or have dramatically different effective population sizes. Unsuitable intervening habitat such as agricultural tracts and roads between existing populations of foxsnakes appears to act as barriers to gene flow, while garter snake movement appears unrestricted by these features. Our findings have important implications for the management of eastern foxsnakes.

Habitat Selection of the Terciopelo (Serpentes: Viperidae: Bothrops asper) in a Lowland Rainforest in Costa Rica

Abstract Despite their high diversity and importance as top predators in many ecosystems, the ecology of many snakes remains poorly understood. This situation is especially true at low latitudes, as few attempts have been made to quantify patterns of space usage by tropical snake species. Here, we describe macro- and microhabitat use by the abundant pit viper Bothrops asper in the lowlands of Costa Rica. Specifically, we used radiotelemetry to monitor nine female and four male adult snakes at La Selva Biological Station between 2004 and 2006. We determined macrohabitat usage and availability on the basis of the movements of individual snakes and analyzed selection using compositional analysis. Microhabitat was quantified by a series of structural characteristics, and groups of locations were compared using multivariate ANOVA and discriminant function analysis. In our study, B. asper demonstrated a positive selection for swamp habitat and avoidance of human-disturbed areas by both male and female snakes. M...

Cross-neutralisation of Australian brown snake, taipan and death adder venoms by monovalent antibodies

An understanding of the cross-neutralisation of snake venoms by antibodies is important for snake antivenom development. We investigated the cross-neutralisation of brown snake ( Pseudonaja textilis) venom, taipan ( Oxyuranus scutellatus) venom and death adder ( Acanthophis antarcticus) with commercial antivenoms and monovalent anti-snake IgG, using enzyme immunoassays, in vitro clotting and neurotoxicity assays. Each commercial antivenom bound all three venoms, and neutralised clotting activity of brown snake and taipan venoms and neurotoxicity of death adder venom. The ‘in-house’ monovalent anti-snake venom IgG raised against procoagulant brown snake and taipan venoms, did not neutralise the neurotoxic effects of death adder venom. However, they did cross-neutralise the procoagulant effects of both procoagulant venoms. This supports the idea of developing antivenoms against groups of snake toxins rather than individual snake venoms.

Biological and proteomic analysis of venom from the Puerto Rican Racer ( Alsophis portoricensis: Dipsadidae)

The Puerto Rican Racer Alsophis portoricensis is known to use venom to subdue lizard prey, and extensive damage to specific lizard body tissues has been well documented. The toxicity and biochemistry of the venom, however, has not been explored extensively. We employed biological assays and proteomic techniques to characterize venom from A. portoricensis anegadae collected from Guana Island, British Virgin Islands. High metalloproteinase and gelatinase, as well as low acetylcholinesterase and phosphodiesterase activities were detected, and the venom hydrolyzed the α-subunit of human fibrinogen very rapidly. SDS-PAGE analysis of venoms revealed up to 22 protein bands, with masses of ∼5–160 kDa; very little variation among individual snakes or within one snake between venom extractions was observed. Most bands were approximately 25–62 kD, but MALDI-TOF analysis of crude venom indicated considerable complexity in the 1.5–13 kD mass range, including low intensity peaks in the 6.2–8.8 kD mass range (potential three-finger toxins). MALDI-TOF/TOF MS analysis of tryptic peptides confirmed that a 25 kDa band was a venom cysteine-rich secretory protein (CRiSP) with sequence homology with tigrin, a CRiSP from the natricine colubrid Rhabdophis tigrinus. The venom was quite toxic to NSA mice ( Mus musculus: LD 50 = 2.1 μg/g), as well as to Anolis lizards ( A. carolinensis: 3.8 μg/g). Histology of the venom gland showed distinctive differences from the supralabial salivary glands (serous vs. mucosecretory), and like the Brown Treesnake ( Boiga irregularis), another rear-fanged snake, serous secretory cells are arranged in densely packed secretory tubules, with little venom present in tubule lumina. These results clearly demonstrate that venom from A. portoricensis shares components with venoms of front-fanged snakes as well as with other rear-fanged species. Venom from A. portoricensis, in particular the prominent metalloproteinase activity, likely serves an important trophic function by facilitating prey handling and predigestion of prey.

Low Temperature Dormancy Affects the Quantity and Quality of the Female Sexual Attractiveness Pheromone in Red-sided Garter Snakes

Low temperature dormancy is a necessary requirement of the annual cycle of most nonmigratory, temperate vertebrates. The red-sided garter snake, Thamnophis sirtalis parietalis, overwinters in communal dens during its prolonged winter dormancy (8 mo), and upon emergence, reproductive behavior of both sexes is maximal. Previous work on this species showed that male courtship behavior is maximally induced after simulated low temperature dormancy. The purpose of this study was to determine whether low temperature dormancy affects the pheromone profiles of individual female red-sided garter snakes. We collected females in the fall at den sites in Manitoba, Canada, and extracted pheromones from individuals at three different time points: fall (field), winter (lab), and spring (lab). Total skin lipid and pheromone fraction masses increased from fall to spring, and pheromone profiles were distinctly different in the fall and spring. Pheromone profiles became dominated by the long-chain, unsaturated methyl ketone components of the blend by the time snakes emerged in the spring. Further, the amounts of both saturated and unsaturated components increased from fall to spring, suggesting significant sex pheromone synthesis was induced by low temperature dormancy.

Evaluation of trap capture in a geographically closed population of brown treesnakes on Guam

SummaryOpen population mark–recapture analysis of unbounded populations accommodates some types of closure violations (e.g. emigration, immigration). In contrast, closed population analysis of such populations readily allows estimation of capture heterogeneity and behavioural response, but requires crucial assumptions about closure (e.g. no permanent emigration) that are suspect and rarely tested empirically.In 2003, we erected a double‐sided barrier to prevent movement of snakes in or out of a 5‐ha semi‐forested study site in northern Guam. This geographically closed population of >100 snakes was monitored using a series of transects for visual searches and a 13 × 13 trapping array, with the aim of marking all snakes within the site. Forty‐five marked snakes were also supplemented into the resident population to quantify the efficacy of our sampling methods. We used the programmarkto analyse trap captures (101 occasions), referenced to census data from visual surveys, and quantified heterogeneity, behavioural response, and size bias in trappability. Analytical inclusion of untrapped individuals greatly improved precision in the estimation of some covariate effects.A novel discovery was that trap captures for individual snakes consisted of asynchronous bouts of high capture probability lasting about 7 days (ephemeral behavioural effect). There was modest behavioural response (trap happiness) and significant latent (unexplained) heterogeneity, with small influences on capture success of date, gender, residency status (translocated or not), and body condition.Trapping was shown to be an effective tool for eradicating large brown treesnakesBoiga irregularis(>900 mm snout‐vent length, SVL).Synthesis and applications.Mark–recapture modelling is commonly used by ecological managers to estimate populations. However, existing models involve making assumptions about either closure violations or response to capture. Physical closure of our population on a landscape scale allowed us to determine the relative importance of covariates influencing capture probability (body size, trappability periods, and latent heterogeneity). This information was used to develop models in which different segments of the population could be assigned different probabilities of capture, and suggests that modelling of open populations should incorporate easily measured, but potentially overlooked, parameters such as body size or condition.

Spatial Biology of Northern Watersnakes (Nerodia sipedon) Living along an Urban Stream

Fifty Nerodia sipedon living along two kilometers of an urban stream in northeastern Pennsylvania were radio-tracked over three activity seasons, yielding more than 2520 relocations. Half the stream length is urbanized, flowing through a city park at the head of the study area and an industrial area at the downstream end; the half between is relatively natural, flowing through a conservation corridor. Individual snakes exhibited high site fidelity. For 82% of relocations, snakes were within a one-meter radius of places they had previously occupied, most often using exactly the same hole, rock, branch, or cover object. Snakes were found to have moved to a different site at 27% of relocations. When snakes moved, they returned to previously occupied places 56% of the time. Females exhibited significantly greater site fidelity than males, and snakes occupying the urban half of the study site exhibited significantly greater site fidelity than snakes found in the natural half. Individuals varied greatly in the amount of space they utilized. Snakes had a mean minimum convex polygon (MCP) activity area of 1.13 ha. Snakes appeared to use the stream to travel between locations separated by more than 100 meters. Original MCPs overestimated space use by including large terrestrial areas that were never occupied by and were unsuitable to snakes. Fixed kernel methods underestimated space use by producing multiple small, disjunct contours. Both methods often largely or completely excluded the stream. To address these problems, we provide additional estimates of space use that sum the MCPs encompassing all of a snake's locations within 100 meters of each other and add the area of stream connecting the most upstream and downstream locations.

Biochemistry and toxicology of toxins purified from the venom of the snake Bothrops asper

The isolation and study of individual snake venom components paves the way for a deeper understanding of the pathophysiology of envenomings – thus potentially contributing to improved therapeutic modalities in the clinical setting – and also opens possibilities for the discovery of novel toxins that might be useful as tools for dissecting cellular and molecular processes of biomedical importance. This review provides a summary of the different toxins that have been isolated and characterized from the venom of Bothrops asper, the snake species causing the majority of human envenomings in Central America. This venom contains proteins belonging to at least eight families: metalloproteinase, serine proteinase, C-type lectin-like, l-amino acid oxidase, disintegrin, DC-fragment, cystein-rich secretory protein, and phospholipase A 2. Some 25 venom proteins within these families have been isolated and characterized. Their main biochemical properties and toxic actions are described, including, in some cases, their possible relationships to the pathologic effects induced by B. asper venom.

Does a Gigantic Insular Snake Grow Faster or Live Longer to be Gigantic? Evidence from a Long-term Field Study

Insular snake populations show bimodal size distributions with giants evolving on islands with large prey size and dwarfs on islands with small prey size. However, there is virtually no published study that examined growth trajectories of wild individual snakes to test whether giant and dwarf populations of a species differ in their growth rates and life spans. In order to address this issue, we compared the growth history of individually marked snakes in three insular and one mainland populations of Elaphe quadrivirgata. Our long-term field study, which started in 1982, suggests that gigantic snakes on Tadanae-jima, the Izu islands, take twice as long (30 to 40 years) to attain maximum snout-vent length as snakes from two non-gigantic insular populations. Our study also clearly demonstrated that snake gigantism is achieved by continuous growth throughout ontogeny rather than extensive growth early in their life. Contrary to expectations, young snakes from the gigantic populations grew more slowly than those of the other populations. We discuss potential proximate mechanisms that cause these different growth trajectories, particularly focusing on the exploitation of large sized avian eggs by older aged snakes, which would be a key factor enabling gigantism of the snake.

Can Exotic Toad Toxins Kill Native Ryukyu Snakes? Experimental and Field Observations on the Effects of Dinodon rufozonatum walli

Bufo marinus is a large toxic toad that was recently introduced to Ishigakijima of the Yaeyama Islands, Southern Ryukyus, Japan. In a previous study, the native Southern Ryukyu snake, Dinodon rufozonatum walli, did not die after ingestion of a single juvenile toad. Considering the current high density of the toads on Ishigakijima, however, it is highly likely that an individual snake may have an opportunity in the field to swallow more than one toad in succession. Therefore, we experimentally investigated the occurrence of voluntary multiple ingestions of juvenile toads by this snake and their effects on the snake. In addition, we obtained from the inhabitants of Ishigakijima some field records of dead snakes that had apparently been killed by the cane toads (sometimes larger than the juveniles used in our experiment). The experiment showed that the snake may often voluntarily seize two or more juvenile toads at once, and may die while swallowing them. These results and the field records suggest that the D. r. walli population on Ishigakijima has been seriously affected by the feral toad population by ingesting this toxic prey.

Snake species distributions and temperate grasslands: A case study from the American tallgrass prairie

Many snake species are declining globally, yet data unavailability in temperate grasslands hinders snake conservation in one of the world’s most endangered biomes. To encourage and inform the conservation of snakes in these regions, I examined snake species diversity and abundance during 2 years of a mark-recapture study at 22 sites located in six American tallgrass prairie preserves in northern Illinois, USA. I emphasized landscape-scale relationships after accounting for covariance with environmental factors at both finer (microhabitat) and broader (regional) scales. A total of 120 snakes representing seven species was captured using drift fence arrays associated with funnel traps and sheet metal cover. The low numbers and diversity of snakes captured, when compared to historic evidence, indicate that since the 1930s Midwestern snake populations have declined. Non-metric multidimensional scaling and Mantel tests demonstrate that differences in snake species composition in remnant and degraded prairies are discernable along gradients of urban and agricultural land cover. However, different patterns of abundance for individual snake species indicate that the relative importance of specific landscape factors differ among species, which has significant conservation implications. Here, I recommend that conservationists use a species-specific approach to manage snake populations. I also stress the need for thorough inventory of snake populations and studies of snake–habitat relationships to advance our understanding of snake ecology and conservation within the little studied temperate grassland habitats of South America and eastern Eurasia.

Body Size, Growth, and Reproduction in a Population of Western Cottonmouths (Agkistrodon piscivorus leucostoma) in the Ozark Mountains of Northwest Arkansas

Abstract Life histories of a species often vary geographically, and comparative studies of populations in different habitats are useful for understanding how environmental variation influences life history. Such studies are currently lacking for most snake species despite their growing importance as model organisms for life history studies. We present life history data for a population of Western Cottonmouths (Agkistrodon piscivorus leucostoma) inhabiting a “riffle–pool” creek system (Rocky Grove) located in the Ozark Mountains in northwest Arkansas and compare our results with those available for other populations. One hundred forty-two individual snakes were captured 283 times from August 1996 through September 2003. Mean snout–vent length (SVL) of adult Rocky Grove A. piscivorus (males 60.8 ± 2.68 cm, n = 47, females 54.9 ± 1.74 cm, n = 47) was among the smallest reported for any population of A. piscivorus. Rocky Grove A. piscivorus also exhibited a low degree of sexual size dimorphism (SSD) compa...

Quantitative Evaluation of Individual Snake Coloration by Use of Principal Components Analysis with Variable Selection

ABSTRACT A common view of biologists for animal coloration is that this characteristic has various ecophysiological functions. Snakes exhibit a variety of colorations in their simple elongated body. Stimulated by their diversified color morphs, various types of studies attempting to elucidate functions of snake colorations have been conducted. Although a few exceptions exist, most of these studies classified color morphs into discrete categories. However, when we treat species having heterogenous color patterns in a single individual and species exhibiting continuous individual variations of coloration, it is often difficult to categorize samples into discrete morphs based on its coloration because we must ignore some characteristics and continuous variations of coloration. Principal components analysis (PCA) is an appropriate method to treat such species because each coloration can be represented by a numerical value as an independent point within a continuum of color variants. However, we cannot know, a...

Community structure and ecology of snakes in fields of oil palm trees (Elaeis guineensis) in the Niger Delta, southern Nigeria

Aspects of community structure and ecology of snakes were studied in the years 2004–2006 in fields of oil palm trees (Elaeis guineensis) of three study areas in Southern Nigeria. A total of 284 individual snakes, belonging to twelve species of three families (seven Colubridae, four Elapidae, one Viperidae), were recorded, including both sighted and captured individuals (not including in this count the individuals that escaped before identification to species level could be made). All the study areas were nearly identical in terms of species composition. Most snakes (about 67%) were recorded during the dry season months, when the fruits of the oil palm ripe, thus attracting lots of organisms that are potential prey for snakes. The most important food items for oil palm snakes were Agama lizards, birds and rodents, but they also fed on skinks, geckos, fruit bats and tree frogs. Snakes were spotted climbing with peak frequencies occurring in the range of 16–18 m above the ground level. In general, oil palm trees within the range of 16–27 m high harboured higher number of snakes. Climbing snakes were nonrandomly positioned on the trees: the highest percentage of snakes (68%) was lodged between the leaf bases and oil palm fruit bunches. The general implications of the given data are discussed.

SPATIAL VARIATION IN PREDATION ATTEMPTS ON ARTIFICIAL SNAKES IN A FIRE-DISTURBED TALLGRASS PRAIRIE

The tallgrass prairie historically burned every 2 to 3 y, removing the litter layer and leaving post-burn environments inhospitable to many terrestrial species. Selection pressures, such as lack of food and shelter and increased predation, are intensified for some species over limited time periods. To quantify predation pressures on large snakes, artificial snakes were placed in recently burned and long-term unburned areas of a grassland system in northeastern Kansas. Any disturbance to the original placement of the model snake was considered a predation attempt. Statistical models were used to estimate daily survival rates of individual artificial snakes within both habitat types. A group effect (burned vs. unburned) was selected as the single top model, garnishing >93% of the support for the data. Survival estimates from this top model indicated artificial snakes in newly burned areas had significantly lower daily survival than those placed within unburned sites. Indirect evidence from destroyed artificial snakes indicated raptors were a major predator on large snakes. Overall herpetofaunal activity in burned areas was low during the first 20 d post-burn, with increasing activity throughout the rest of the season. However, activity within unburned areas was constant throughout the spring. Burning tallgrass prairie likely increases predation pressure on large snakes in the area for 1 to 2 mo following the burn due to the lack of cover against aerial predators.

Snake Bite: Pit Vipers

Pit vipers are the largest group of venomous snakes in the United States and are involved in an estimated 150,000 bites annually of dogs and cats. The severity of any pit viper bite is related to the volume and toxicity of the venom injected as well as the location of the bite, which may influence the rate of venom uptake. The toxicity of rattlesnake venom varies widely. It is possible for pit vipers' venom to be strictly neurotoxic with virtually no local signs of envenomation. Venom consists of 90% water and has a minimum of 10 enzymes and 3 to 12 nonenzymatic proteins and peptides in any individual snake. The onset of clinical signs after envenomation may be delayed for several hours. The presence of fang marks does not indicate that envenomation has occurred, only that a bite has taken place. Systemic clinical manifestations encompass a wide variety of problems including pain, weakness, dizziness, nausea, severe hypotension, and thrombocytopenia. The victim's clotting abnormalities largely depend upon the species of snake involved. Venom induced thrombocytopenia occurs in approximately 30% of envenomations. Many first aid measures have been advocated for pit viper bite victims, none has been shown to prevent morbidity or mortality. Current recommendations for first aid in the field are to keep the victim calm, keep the bite site below heart level if possible, and transport the victim to a veterinary medical facility for primary medical intervention. The patient should be hospitalized and monitored closely for a minimum of 8 hours for the onset of signs of envenomation. The only proven specific therapy against pit viper envenomation is the administration of antivenin. The dosage of antivenin needed is calculated relative to the amount of venom injected, the body mass of the victim, and the bite site. The average dosage in dogs and cats is 1 to 2 vials of antivenin.

Influence of meal size on postprandial thermophily in cornsnakes (Elaphe guttata)

Postprandial thermophily occurs because snakes presumably select body temperatures to maximize digestive functions. However, there seems to be little to no literature available on meal size affecting the degree of postprandial thermophily in snakes. We were interested in determining if meal size influenced post-feeding thermoregulation. To test this, we placed individual snakes into linear thermal gradients with floor temperatures ranging from 10 ± 0.5 °C to 40 ± 1.0 °C. After a 24 h habituation period, substrate temperatures were measured underneath the snake's body, 1/3 of the way down its length, at 3-hour intervals from 0900 to 1800 h. Each snake was monitored under three different conditions: during a fast, after ingesting a 5% body mass meal, and after ingesting a 10% body mass meal. The size of the meal had a significant effect (P=0.0365) on selected substrate temperatures.