Small Snakes Research Articles

Transcriptomic basis for an antiserum against Micrurus corallinus (coral snake) venom

BackgroundMicrurus corallinus (coral snake) is a tropical forest snake belonging to the family Elapidae. Its venom shows a high neurotoxicity associated with pre- and post-synaptic toxins, causing diaphragm paralysis, which may result in death. In spite of a relatively small incidence of accidents, serum therapy is crucial for those bitten. However, the adequate production of antiserum is hampered by the difficulty in obtaining sufficient amounts of venom from a small snake with demanding breeding conditions. In order to elucidate the molecular basis of this venom and to uncover possible immunogens for an antiserum, we generated expressed sequences tags (ESTs) from its venom glands and analyzed the transcriptomic profile. In addition, their immunogenicity was tested using DNA immunization.ResultsA total of 1438 ESTs were generated and grouped into 611 clusters. Toxin transcripts represented 46% of the total ESTs. The two main toxin classes consisted of three-finger toxins (3FTx) (24%) and phospholipases A2 (PLA2s) (15%). However, 8 other classes of toxins were present, including C-type lectins, natriuretic peptide precursors and even high-molecular mass components such as metalloproteases and L-amino acid oxidases. Each class included an assortment of isoforms, some showing evidence of alternative splicing and domain deletions. Five antigenic candidates were selected (four 3FTx and one PLA2) and used for a preliminary study of DNA immunization. The immunological response showed that the sera from the immunized animals were able to recognize the recombinant antigens.ConclusionBesides an improvement in our knowledge of the composition of coral snake venoms, which are very poorly known when compared to Old World elapids, the expression profile suggests abundant and diversified components that may be used in future antiserum formulation. As recombinant production of venom antigens frequently fails due to complex disulfide arrangements, DNA immunization may be a viable alternative. In fact, the selected candidates provided an initial evidence of the feasibility of this approach, which is less costly and not dependent on the availability of the venom.

Food Habits of the Plains Garter Snake (Thamnophis radix) at the Northern Limit of Its Range

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.

Use of an Active Ant Nest as a Hibernaculum by Small Snake Species

Use of ant or termite nests (active and inactive) as nest sites by a variety of vertebrate species is well-documented (Riley et al. 1985; Scherba 1965), as are a number of snake genera with chemical and/or morphological specializations that facilitate ant-snake commensalisms (Holm 2008). Less studied is the use of (in particular) ant nests as hibernacula by non-specialist snakes, and the most frequently cited of these involve inactive ant nests (Carpenter 1953; Lang 1971) or ones with very few ants present (Criddle 1937). When ants have been noted as present, they have been identified (sometimes tenuously, Criddle 1937) as of the genus Formica, widespread in North America. Cervone (1983:p140) noted an association between Virginia valeriae pulchra, closely related to Kansas V. v. elegans, and the ant Formica exsectoides. These snakes (plus juvenile Diadophis and one adult Thamnophis brachystoma) hibernated in abandoned mounds. “near the water table.” Cervone (1983:p34) also wrote that “one does not find V. v. pulchra under the same rock with specimens of Formica exsectoides but it may share its habitat with other species of ants.”

Variation in size of cover used by watersnakes ( Nerodia): Do smaller snakes use smaller rocks?

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.

At the lower size limit in snakes: two new species of threadsnakes (Squamata: Leptotyphlopidae: Leptotyphlops) from the Lesser Antilles

Islands are viewed as natural evolutionary laboratories for terrestrial organisms because they have boundaries that limit dispersal and often reveal evolutionary patterns and mechanisms. One such pattern is that the smallest and largest species of different types of tetrapod animals are frequently found on islands. Here I describe two new diminutive species of snakes of the genus Leptotyphlops from the Lesser Antilles: one from Saint Lucia and the other from Barbados. The one from Barbados is the smallest species of snake and has a total adult length of approximately 100 mm. Limited evidence indicates a clutch size of one and a greatly elongated egg shape (length /width). Comparison of egg shapes in snakes indicates that the shape is a packaging phenomenon, related primarily to the shape of the available body cavity and clutch size. For a clutch size of one, expected egg shape is eight whereas expected egg shape drops to two at a clutch size of ten. The body shape of snakes, defined as snout-to-vent length divided by width, also varies and influences the shape of snake eggs. The smallest snakes are typically stout-bodied with shapes of 30–35 whereas the longest snakes usually are more elongate, with shapes of 45–50. The allometry of organ size also affects clutch size and shape, because the smallest snakes have the smallest proportion of body cavity space available for reproduction. The best explanation for the observation of body size extremes on islands is that colonizing species have adapted to open ecological niches that would otherwise be occupied on the mainland. Island colonists encounter novel environments and reduced interspecific competition, allowing species to evolve physical traits, including extremes in size, not normally seen on continents. However, the lower limit of adult size appears to be constrained by the allometry of morphology, physiology, and reproduction. The smallest tetrapods have small clutches, usually one egg or young, and offspring that are relatively large. In the smallest snakes, offspring are one-half of the length of adults, compared with 10% adult length in the case of large species of snakes. Thus the evolutionary tradeoff between number and size of offspring appears to have reached a size boundary in these species, limiting the evolution of yet smaller species.

Bluffing and Waiting: Handling Effects and Post‐Release Immobility in a Death‐Feigning Snake (Natrix natrix)

AbstractTonic 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.

Response of a Reptile Guild to Forest Harvesting

Despite the growing concern over reptile population declines, the effects of modern industrial silviculture on reptiles have been understudied, particularly for diminutive and often overlooked species such as small-bodied snakes. We created 4 replicated forest-management landscapes to determine the response of small snakes to forest harvesting in the Coastal Plain of the southeastern United States. We divided the replicated landscapes into 4 treatments that represented a range of disturbed habitats: clearcut with coarse woody debris removed; clearcut with coarse woody debris retained; thinned pine stand; and control (unharvested second-growth planted pines). Canopy cover and ground litter were significantly reduced in clearcuts, intermediate in thinned forests, and highest in unharvested controls. Bare soil, maximum air temperatures, and understory vegetation all increased with increasing habitat disturbance. Concomitantly, we observed significantly reduced relative abundance of all 6 study species (scarletsnake[Cemophora coccinea], ring-neck snake[Diadophis punctatus], scarlet kingsnake[Lampropeltis triangulum], red-bellied snake[Storeria occipitomaculata], southeastern crowned snake[Tantilla coronata], and smooth earthsnake[Virginia valeriae]) in clearcuts compared with unharvested or thinned pine stands. In contrast, the greatest relative snake abundance occurred in thinned forest stands. Our results demonstrate that at least one form of forest harvesting is compatible with maintaining snake populations. Our results also highlight the importance of open-canopy structure and ground litter to small snakes in southeastern forests and the negative consequences of forest clearcutting for small snakes.

Brown treesnake (Boiga irregularis) trappability: Attributes of the snake, environment and trap

We examined three classes of factors that may influence brown treesnake (Boiga irregularis) trappability on Guam: (1) attributes of the snake, (2) attributes of the environment and (3) attributes of the trap. The attributes of the snake we considered included body condition, length and sex. Heavier snakes for a given size (better body condition) moved less and were less easily trapped. Longer snakes were easier to trap. Males were also slightly more easily trapped than females. We compared brown treesnake trappability between two study sites that differed greatly in the abundance of diurnal skinks, an important prey item for smaller snakes. We predicted that snakes, especially small individuals (<800 mm snout-vent length), would be more easily trapped in the low prey environment, a result that received only weak support from our data. However, small snakes were rarely trapped under any circumstance. We also predicted that diurnal foraging would be observed in the site with a higher density of diurnal prey, but daytime snake captures were negligible at both sites. Two attributes of traps that we varied were attractant (mouse vs. skink) and entrance flaps (present vs. absent). Traps with mice as attractant registered 6-16 fold more snake captures. We found little influence of entrances on captures. These modulators of brown treesnake trappability may have analogues in a variety of species, especially species that undergo an ontogenetic shift in diet.

Molecular and phenotypic diversity in Chionactis occipitalis (Western Shovel-nosed Snake), with emphasis on the status of C. o. klauberi (Tucson Shovel-nosed Snake).

Chionactis occipitalis (Western Shovel-nosed Snake) is a small colubrid snake inhabiting the arid regions of the Mojave, Sonoran, and Colorado deserts. Morphological assessments of taxonomy currently recognize four subspecies. However, these taxonomic proposals were largely based on weak morphological differentiation and inadequate geographic sampling. Our goal was to explore evolutionary relationships and boundaries among subspecies of C. occipitalis, with particular focus on individuals within the known range of C. o. klauberi (Tucson Shovel-nosed snake). Population sizes and range for C. o. klauberi have declined over the last 25 years due to habitat alteration and loss prompting a petition to list this subspecies as endangered. We examined the phylogeography, population structure, and subspecific taxonomy of C. occipitalis across its geographic range with genetic analysis of 1100 bases of mitochondrial DNA sequence and reanalysis of 14 morphological characters from 1543 museum specimens. We estimated the species gene phylogeny from 81 snakes using Bayesian inference and explored possible factors influencing genetic variation using landscape genetic analyses. Phylogenetic and population genetic analyses reveal genetic isolation and independent evolutionary trajectories for two primary clades. Our data indicate that diversification between these clades has developed as a result of both historical vicariance and environmental isolating mechanisms. Thus these two clades likely comprise ‘evolutionary significant units’ (ESUs). Neither molecular nor morphological data are concordant with the traditional C. occipitalis subspecies taxonomy. Mitochondrial sequences suggest specimens recognized as C. o. klauberi are embedded in a larger geographic clade whose range has expanded from western Arizona populations, and these data are concordant with clinal longitudinal variation in morphology.

Benign Fasciculations and other poems

One day, unprovoked, a small snake ripples in my thigh, unbidden as a tic around the eye. Something broken to congeal the honey in my flesh, a beehive gone awry. Under a harsh light, you report the nexus spread like a brush-fire’s nascent flame to calves and head. A syncopated wave of muscular babble unrecruited by anything I’ve done or said, and then I tell you I’m dead; a droplet poised at the end of life’s spout. Just a few months ’till my spinal cord rots, breath is snuffed, and crawlers pick my femurs clean. At night I shout, pursued by visions of catacombs, of men I’ve tended, slowly wasted to …

Smallest limited snakes

Smallest limited snakes

BUMPUS IN THE SNAKE DEN: EFFECTS OF SEX, SIZE, AND BODY CONDITION ON MORTALITY OF RED-SIDED GARTER SNAKES

Abstract Huge breeding aggregations of red-sided garter snakes (Thamnophis sirtalis parietalis) at overwintering dens in Manitoba provide a unique opportunity to identify sources of mortality and to clarify factors that influence a snake's vulnerability to these factors. Comparisons of sexes, body sizes, and body condition of more than 1000 dead snakes versus live animals sampled at the same time reveal significant biases. Three primary sources of mortality were identified. Predation by crows, Corvus brachyrhynchos (590 snakes killed), was focussed mostly on small snakes of both sexes. Crows generally removed the snake's liver and left the carcass, but very small snakes were sometimes brought back to the nest. Suffocation beneath massive piles of other snakes within the den (301 dead animals) involved mostly small males and (to a lesser extent) large females; snakes in poor body condition were particularly vulnerable. Many emaciated snakes (in= 142, mostly females) also died without overt injuries, probably due to depleted energy reserves. These biases in vulnerability are readily interpretable from information on behavioral ecology of the snakes. For example, sex biases in mortality reflect differences in postemergence behavior and locomotor capacity, the greater attractiveness of larger females to males, and the high energy costs of reproduction for females.

Souvenirs from Ganymede

Souvenirs from Ganymede Juan Martinez (bio) The snakes had nowhere to go, so they ended up in our homes. We extracted four from our A/C unit. They crawled in and wouldn't be found till the unit malfunctioned and stank up the house, and little drama was made of the extraction. We lived with live snakes and were okay with dead ones. The live ones ran through our gardens. A man with an unkempt beard was called upon to deal with those thought poisonous: he doused them in gasoline, lit them on fire, let them burn, and swung them into a ravine. I must have watched that arc a few times. Mostly I remember the snakes found in the A/C unit—already dead, probably not at all that bright to begin with, sad, harmless. They made their way to our ducts from 1979 to 1983. We lived in Guri, a worker's camp in Venezuela, on a low dimple adjoining what would become, when completed, one of the biggest dams in the world. Caterpillar trucks cleared the land in wide sweeps. The forests of Canaima burned, the smell sweet. We lived in paradise and were expelling the snakes. The American and Canadian workers living in the camp took us aside and warned us about corals, which children chased because they were small snakes, hard to find, colorful, and had no desire to be caught. No one we knew was bitten by a coral snake. Corals were shy, as were scorpions, which we sometimes found when we shook our sneakers before putting them on, although we put them on many times without shaking (we often forgot) and nothing happened. Nothing happened with the arañas monas either. They were nothing more than particularly large tarantulas. They looked otherworldly, extraterrestrial, and they scattered out of unexpected places. Closets. Boxes. Pants pockets. Barbecue pits. One scattered out hissing, on fire, out of the coals. It jumped out of the [End Page 90] grill and onto a table and into the ground. It moved fast and passed right by me, a little alien on fire looking for a forest and finding nothing but pre-fabs and shrubbery. Once the tarantula left, Peruvian friends of my parents grilled anticuchos, marinated cow hearts, which I ate again only recently and which are better than you might think, especially if you don't know what they are before you eat them. The dish took me right back to Guri. These friends, Lucho and Lucia, also prepared exquisite fish seviches: chunks of raw fish marinated in lemon juice. Our Argentinean neighbors introduced me to mate and ark clams. People had flown from all parts of the world because Venezuela had struck oil and had too much money and didn't know what to do with it. When they arrived in Guri, my father was twenty-five, a scholarship kid, an industrial engineer who turned down a Fulbright because he had just met the person who follows this dash—my mother was twenty-two, bright, a beauty who received a call from a former suitor on her honeymoon, the boy heartbroken and telling her that if she did not leave my father he would kill himself. She told him to go to hell. My mother was seventeen when she married, my father twenty. They are extraordinarily good-looking people—toned, symmetrical, and (during their twenties, thirties, forties, and fifties) eerily ageless, young. They are in their sixties now and could pass for people in their early forties. Their crowd in Guri was mostly young and unmarried. They spent their weekends on beaches, following long, artfully choreographed car trips. I was the only child for a long time. When I visit my parents' friends or when they visit me, they tell me so, that I was this little thing chattering away with all the twenty-somethings. They break out photo albums (they carry them on trips and e-mail forgotten prints—what happened for them during their twenties never repeated itself, I don't think, that combination of oil-boom, disposable income, youth, free time; in sharing these photographs they are confirming an unlikely moment in the unlikeliest...

USE OF PLASTICINE REPLICA SNAKES TO ELICIT ANTIPREDATOR BEHAVIOR IN THE CALIFORNIA GROUND SQUIRREL (SPERMOPHILUS BEECHEYI)

Abstract We placed 72 plasticine replicas of large and small snakes near a California ground squirrel (Spermophilus beecheyi) colony in San Diego County, California. Ground squirrels aggressively confronted both large and small replica snakes. Ground squirrels were more aggressive when attacking small replicas relative to large. Ground squirrels bit the smaller replicas a greater number of times, concentrating their attacks near the head of the replica. Large replicas were attacked more frequently near the tail. From the results we conclude: 1) California ground squirrels recognize increased risk of attacking larger versus smaller snakes, and 2) use of plasticine replicas is an effective method to investigate antipredator behavior of prey.

Diet of the black-headed heron Ardea melanocephala during the breeding season in South African grasslands

The diet of the black-headed heron was studied using analysis of pellets and prey remnants (225 prey items identified) collected from four sites in South African Highveld Grassland, transformed into cultivated fields. Small vertebrates comprised the staple food of chicks. Rodents were the most important vertebrate prey. Otomys irroratus comprised ca. 50% of the total biomass of vertebrate prey consumed. The diet was supplemented by small lizards, snakes, frogs and fishes. Grasshoppers, beetles, crabs and other arthropods were occasionally preyed upon.

Do juvenile gape‐limited predators compensate for their small size when feeding?

AbstractWhen juvenile and adult animals occur syntopically, juveniles are at a distinct performance disadvantage due to their absolutely small size. Yet, optimal foraging theory predicts that juvenile predators should feed efficiently in order to compete with adults for food, and to minimize their exposure to predators. Previous authors have suggested that one way for juvenile animals to accomplish these ecological tasks is by increasing their overall feeding performance relative to adults (compensation hypothesis). Nonetheless, only a handful of studies have tested whether juvenile animals have increased feeding performance (e.g. decreased ingestion and/or handling times relative to body size) compared with adults. We tested this hypothesis by examining the ontogeny of head dimensions and feeding performance (ingestion time and number of mandibular protractions) on fish prey for broad‐banded water snakesNerodia fasciata. Individuals were fed fish scaled in a 1:1 ratio to their head width. All head dimensions scaled with significant negative allometry versus body size, and thus smaller snakes had relatively larger heads for their body size compared with larger snakes. By contrast, most head variables (except head volume) exhibited positive allometry versus head length, demonstrating that larger snakes had larger head dimensions relative to head size compared with smaller snakes. In the performance trials, smaller snakes had worse feeding performances when feeding on similarly sized fish prey (relative to their head width) compared with larger snakes. Therefore, these data show that smaller water snakes do not compensate for their size through increased feeding performance.

Does rock disturbance by superb lyrebirds (Menura novaehollandiae) influence habitat selection by juvenile snakes?

Abstract: Vertebrates that destroy or disturb habitats used by other animals may influence habitat selection by sympatric taxa. In south‐east Australian forests, superb lyrebirds (Menura novaehollandiae) displace soil, leaf litter and rocks during their daily foraging activities. We investigated whether superb lyrebirds disturb small sandstone rocks that endangered broad‐headed snakes Hoplocephalus bungaroides and common small‐eyed snakes Cryptophis nigrescens use as diurnal thermoregulatory sites. To estimate the frequency of lyrebird rock disturbance, and to assess whether lyrebirds also attack small snakes, we placed 900 plasticine snake replicas under stones on rock and soil substrates along transects on three sandstone plateaux. Because juvenile snakes must select retreat sites that simultaneously allow them to thermoregulate and minimize predation risk, we quantified the thermal environments underneath stones on rock and soil substrates. During the 6‐week experiment, animals disturbed rocks on soil substrates twice as often (16.9%) as rocks lying on rock substrates (8.2%). Disturbed rocks were significantly smaller and lighter than undisturbed rocks on both substrates. Lyrebirds were the major agents of disturbance, and attacked 40% of snake models under disturbed rocks. Rocks on soil substrates conferred the greatest thermal benefits to snakes, but both species of snake avoided these microhabitats in the field. Instead, juvenile snakes selected rocks on rock substrates, and sheltered under stones that were too heavy for superb lyrebirds to disturb. By disturbing rocks over millennia, superb lyrebirds not only have shaped the physical landscape, but also may have exerted strong selection on habitat selection by sympatric snakes.

Why don't small snakes bask? Juvenile broad‐headed snakes trade thermal benefits for safety

Previous studies have suggested that most small Australian elapid snakes are nocturnal and rarely bask in the open because of the risk of predation by diurnal predatory birds. Because the physiology and behaviour of reptiles is temperature dependent, staying in refuges by day can entail high thermoregulatory costs, particularly for juveniles that must grow rapidly to maximise their chances of survival. We investigated whether the risk of predation deters juveniles of the endangered broad‐headed snake (Hoplocephalus bungaroides) from basking, and if so, whether there are thermal costs associated with refuge use. To estimate avian attack rates on snakes, we placed 900 plasticine snake replicas in sunny locations and underneath small stones on three sandstone plateaus for 72 h. At the same time we quantified the thermal benefits of basking vs refuge use. On sunny days, juveniles could maintain preferred body temperatures for 4.7 h by basking but only for 2.0 h if they remained inside refuges. Our predation experiment showed that basking has high costs for juvenile snakes. Predators attacked a significantly higher proportion of exposed models (13.3%) than models under rocks (1.6%). Birds were the major predators of exposed models (75% of attacks), and avian predation did not vary across the landscape. By trading heat for safety, juvenile H. bungaroides decreased the potential time period that they could maintain preferred body temperatures by 57%. Thermal costs of refuge use may therefore contribute to the slow growth and late maturation of this endangered species. Our results support the hypothesis that nocturnal activity in elapid snakes has evolved to minimise the risk of avian predation.

Effects of size and behavior on aerial performance of two species of flying snakes (Chrysopelea)

Aerial locomotion in snakes (genus Chrysopelea) is kinematically distinct from any other type of gliding or powered flight, with prominent, high amplitude body undulations visually dominating the behavior. Because it is not known how flying snakes produce aerodynamic forces in flight, the factors that determine snake flight performance are not clear. In this study, the effects of size and behavior on aerial performance were examined both within a species (C. paradisi) and between two species (C. paradisi and C. ornata), using stepwise multiple regressions to identify relevant variables. Smaller C. paradisi traveled farther than larger snakes at lower sinking speeds, with trajectories that shallowed more quickly and reached lower minimum glide angles. Although wing loading increased faster than expected for isometric size increase, wing loading per se was not responsible for performance differences between large and small snakes. Snakes with higher interactions between relative undulation amplitude and body size transitioned out of the initial acceleration phase at higher airspeeds and sinking speeds, and attained higher maximum airspeeds and horizontal speeds; snakes that used higher average relative amplitudes transitioned out of the initial acceleration phase at higher horizontal speeds. Undulation frequency was not significantly related to any performance variable within C. paradisi and was not significantly different between the two species, suggesting that this variable (in contrast to relative undulation amplitude) may have a minor influence on the aerodynamic mechanism of force production in snake flight. C. paradisi and C. ornata differed significantly in most performance comparisons. C. ornata were more massive than C. paradisi at any given body length and in general exhibited poorer gliding performance than C. paradisi. This study contributes towards understanding how an unconventional body form and kinematics can produce a novel mode of aerial locomotion in a vertebrate glider.

Geographic and Size-related Variation in the Diet of Insular Populations of the Northern Watersnake

I studied microgeographic and size-related variation in the diet composition of the Northern Watersnake Nerodia sipedon sipedon in the Beaver Archipelago of Lake Michigan. Snakes from Lake Michigan shoreline sites were piscivorous whereas snakes from interior sites on Beaver Island ate mostly amphibians. Sculpin (Cottus sp.) were the dominant prey of all size classes, but a gradual size-related shift in diet may be occurring in archipelago snakes. Large snakes tended to eat larger prey than small snakes and to drop the smallest prey from their diets, but overlap in prey size occurred among all size classes of snakes. The diet composition of snakes from different sites is likely a reflection of local differences in prey abundance, as found in several previous studies. The overlap in prey size and prey type among snake size classes contradicts the results of some previous studies of Nerodia sp. and merits further investigation.