Interactions between locomotion,feeding, and bodily elongation during the evolution of snakes

Information from lizard lineages that have evolved a highly elongate (snake‐like) body form may clarify the selective forces important in the early evolution of snakes. Lizards have evolved bodily elongation via two distinct routes: as an adaptation to burrowing underground or to rapid locomotion above ground. These two routes involve diametrically opposite modifications to the body plan. Burrowing lizards have elongate trunks, small heads, short tails, and relatively constant body widths, whereas surface‐active taxa typically have shorter trunks, wider heads, longer tails, and more variable body widths. Snakes resemble burrowing rather than surface‐active (or aquatic) lizards in these respects, suggesting that snakes evolved from burrowing lizards. The trunk elongation of burrowing lizards increases the volume of the alimentary tract, so that an ability to ingest large meals (albeit consisting of small individual prey items) was present in the earliest snakes. Subsequent shifts to ingestion of wide‐bodied prey came later, after selection dismantled other gape‐constraining morphological attributes, some of which may also have arisen as adaptations to burrowing through hard soil (e.g. relatively small heads, rigid skulls). Adaptations of snake skulls to facilitate ingestion of large prey have evolved to compensate for the reduction of relative head size accompanying bodily elongation; relative to predator body mass, maximum sizes of prey taken by snakes may not be much larger than those of many lizards. This adaptive scenario suggests novel functional links between traits, and a series of testable predictions about the relationships between squamate morphology, habitat, and trophic ecology. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 293–304.     

Parental defence on the reef: antipredator tactics of coral‐reef fishes against egg‐eating seasnakes

On coral reefs in New Caledonia, the eggs of demersal‐spawning fishes are consumed by turtle‐headed seasnakes (Emydocephalus annulatus). Fish repel nest‐raiding snakes by a series of tactics. We recorded 232 cases (involving 22 fish species) of antipredator behaviour towards snakes on a reef near Noumea. Blennies and gobies focused their attacks on snakes entering their nests, whereas damselfish (Pomacentridae) attacked passing snakes, as well as nest‐raiders (reflecting territorial defence). Biting the snake was the most common form of attack, although damselfish and blennies also slapped snakes with the tail, or (blennies only) plugged the nest entrance with the parent fish's body. Gobies rarely defended the nest, although they sometimes bit or threw sand at the snake. A snake was more likely to flee if it was attacked before it began feeding rather than after it found the eggs (82% versus 3% repelled) and if bitten on the head rather than the body (68% versus 53%). Tail‐slaps were not effective, although plugging the burrow and throwing sand often caused snakes to flee. These strong patterns reflect phylogenetic variation in fish behaviour (e.g. damselfish detect a snake approach sooner than do substrate‐dwelling blennies and gobies) coupled with intraspecific variation in snake diets. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 415–425.     

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

When 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 snakes Nerodia 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.     

Length–mass allometry in snakes

Body size and body shape are tightly related to an animal's physiology, ecology and life history, and, as such, play a major role in understanding ecological and evolutionary phenomena. Because organisms have different shapes, only a uniform proxy of size, such as mass, may be suitable for comparisons between taxa. Unfortunately, snake masses are rarely reported in the literature. On the basis of 423 species of snakes in 10 families, we developed clade‐specific equations for the estimation of snake masses from snout–vent lengths and total lengths. We found that snout–vent lengths predict masses better than total lengths. By examining the effects of phylogeny, as well as ecological and life history traits on the relationship between mass and length, we found that viviparous species are heavier than oviparous species, and diurnal species are heavier than nocturnal species. Furthermore, microhabitat preferences profoundly influence body shape: arboreal snakes are lighter than terrestrial snakes, whereas aquatic snakes are heavier than terrestrial snakes of a similar length. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●● , ●●–●●.     

Molecular systematics of neotropical cat-eyed snakes: a test of the monophyly of Leptodeirini (Colubridae: Dipsadinae) with implications for character evolution and biogeography

The Leptodeirini has been presumed to be a monophyletic assemblage based on albumin immunological data and morphology and consisted of neotropical cat-eyed snakes ( Leptodeira ), blunt-headed vine snakes ( Imantodes ), nightsnakes ( Eridiphas , Hypsiglena , and Pseudoleptodeira ), and the cloud forest snake ( Cryophis ). In the present study, approximately 1.4 kb of mitochondrial DNA sequence data (from cob and nad4 ) were collected to test the monophyly of the Leptodeirini. These data were analysed using maximum parsimony, maximum likelihood, and Bayesian methods. None of the results supported the monophyly of the Leptodeirini. There was strong support for a clade containing Imantodes and Leptodeira , and another clade containing the nightsnakes, with the latter placed closer to Cryophis and other dipsadine genera ( Sibon , Dipsas , and Atractus ). This partial reassessment of the Dipsadinae infers the group to have an ancestral condition of being rear-fanged, mildly venomous, and feeding on ectothermal vertebrates, with a more derived radiation that has lost the rear-fanged, venomous condition and has a diet specialized on invertebrates. A brief discussion on the biogeography of the dipsadines shows the group to be much older (Palaeocene), consistent with earlier views, as opposed to a more recent (Miocene) hypothesis, as has been recently suggested.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 483–500.     

Functional and ecological relevance of intraspecific variation in body size and shape in the lizard Podarcis melisellensis (Lacertidae)

Within populations, individual animals may vary considerably in morphology and ecology. The degree to which variation in morphology is related to ecological variation within a population remains largely unexplored. We investigated whether variation in body size and shape among sexes and age classes of the lizard Podarcis melisellensis translates in differential whole-animal performance (sprint speed, bite force), escape and prey attack behaviour in the field, microhabitat use and diet. Male and female adult lizards differed significantly in body size and head and limb proportions. These morphological differences were reflected in differences in bite strength, but not in sprint speed. Accordingly, field measurements of escape behaviour and prey attack speed did not differ between the sexes, but males ate larger, harder and faster prey than females. In addition to differences in body size, juveniles diverged from adults in relative limb and head dimensions. These shape differences may explain the relatively high sprint and bite capacities of juvenile lizards. Ontogenetic variation in morphology and performance is strongly reflected in the behaviour and ecology in the field, with juveniles differing from adults in aspects of their microhabitat use, escape behaviour and diet.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 251–264.     

Ontogeny of intersexual head shape and prey selection in the pitviper Agkistrodon piscivorus

Different animal intraspecific classes commonly differ in their prey selection. Such differences in feeding ecology are thought to reduce resource competition between classes, but other factors (i.e. behavioural, morphological, and physiological differences) also contribute to this widespread phenomenon. Although several studies have correlated the size of the feeding apparatus with prey selection in many animals, few studies have examined how the shape of the feeding apparatus is related to prey selection. Furthermore, even though the dietary regimen of many animals changes during ontogeny, few studies have examined how shape changes in the feeding apparatus may be related to these ontogenetic dietary shifts. Here we address these issues by examining how head shape, head size and prey selection change over ontogeny in adult males, adult females and juveniles of the cottonmouth snake Agkistrodon piscivorus . Our scaling data for head characteristics showed that all head measurements in adult male and female A. piscivorus scaled with significant negative allometry, whereas juvenile head measurements typically scaled isometrically, except for head volume (positive) and head length (negative). Thus, juveniles have relatively broad and high, but short, heads. Large adult male and female A. piscivorus have relatively small head dimensions overall. Thus, juveniles appear to undergo a rapid change in head volume, which subsequently slows considerably as sexual maturity is achieved. However, our multivariate analysis of size-adjusted head dimensions showed that juveniles differed only slightly in their head shape compared with adult male and female A. piscivorus . In general, prey size increased with snake size across all age and sex groups, but an ontogenetic shift in prey type was not detected in either males or females.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 151–159.     

How snakes eat snakes: the biomechanical challenges of ophiophagy for the California kingsnake, Lampropeltis getula californiae (Serpentes: Colubridae)

In this study we investigated how ophiophagous snakes are able to ingest prey snakes that equal or exceed their own length. We used X-ray video, standard video, dissection, and still X-rays to document the process of ophiophagy in kingsnakes (Lampropeltis getula) feeding on corn snakes (Elaphe guttata). Most kingsnakes readily accepted the prey snakes, subdued them by constriction, and swallowed them head first. In agreement with previous observations of ophiophagy, we found that the predator snake forces the vertebral column of the prey snake to bend into waves. These waves shorten the prey's body axis and allow it to fit inside the gastrointestinal (GI) tract and body cavity of the predator. Dissection of a kingsnake immediately following ingestion revealed extensive longitudinal stretching of the anterior portion of the GI tract (oesophagus and stomach), and no visible incursion of the prey into the intestine. X-ray video of ingestion showed that the primary mechanism of prey transport was the pterygoid walk, with some contribution from concertina-like compression and extension cycles of the predator's vertebral column in two out of three observations. Complete digestion was observed in only one individual, as others regurgitated before digestion was finished. X-ray stills taken every 4 days following ingestion revealed that the corn snakes were about half digested within the first 4 days, and digestion was complete within 15 days.     

Not so rare snakes: a revision of the Geophis sieboldi group (Colubridae: Dipsadinae) in lower Central America and Colombia

The Geophis sieboldi species group is composed of 16 currently recognized species distributed from Mexico to Colombia. Within this group, snakes of populations referred to the Geophis brachycephalus complex of lower Central America and Colombia display a remarkable polychromatism and the systematic status of these and other populations is problematic. The present study provides an analysis, including multivariate techniques, of variation in scalation, coloration, relative tail length and hemipenes to clarify the specific allocation of the populations belonging to this clade. Our results confirm the validity of three previously described taxa, namely G. brachycephalus , G. nigroalbus and G. talamancae , with reassignments of several populations previously referred to G. brachycephalus . In addition we recognize as a new species a suite of western Panama Geophis previously of uncertain status. We further provide a review of all other members of the G. sieboldi group in lower Central America and Colombia based on material obtained since the last revision of the group. Basic synonymies, diagnostics and known distributions are included for the treated taxa. Dietary guild, possible venomous coral snake mimicry and distributional anomalies for the group are discussed.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 153 , 561–599.     

Feeding behavior and venom toxicity of coral snake Micrurus nigrocinctus (Serpentes: Elapidae) on its natural prey in captivity

The feeding behavior and venom toxicity of the coral snake Micrurus nigrocinctus (Serpentes: Elapidae) on its natural prey in captivity were investigated. Coral snakes searched for their prey (the colubrid snake Geophis godmani) in the cages. Once their preys were located, coral snakes stroke them with a rapid forward movement, biting predominantly in the anterior region of the body. In order to assess the role of venom in prey restraint and ingestion, a group of coral snakes was 'milked' in order to drastically reduce the venom content in their glands. Significant differences were observed between snakes with venom, i.e., 'nonmilked' snakes, and 'milked' snakes regarding their behavior after the bite. The former remained hold to the prey until paralysis was achieved, whereas the latter, in the absence of paralysis, moved their head towards the head of the prey and bit the skull to achieve prey immobilization by mechanical means. There were no significant differences in the time of ingestion between these two groups of coral snakes. Susceptibility to the lethal effect of coral snake venom greatly differed in four colubrid species; G. godmani showed the highest susceptibility, followed by Geophis brachycephalus, whereas Ninia psephota and Ninia maculata were highly resistant to this venom. In addition, the blood serum of N. maculata, but not that of G. brachycephalus, prolonged the time of death of mice injected with 2 LD(50)s of M. nigrocinctus venom, when venom and blood serum were incubated before testing. Subcutaneous injection of coral snake venom in G. godmani induced neurotoxicity and myotoxicity, without causing hemorrhage and without affecting heart and lungs. It is concluded that (a) M. nigrocinctus venom plays a role in prey immobilization, (b) venom induces neurotoxic and myotoxic effects in colubrid snakes which comprise part of their natural prey, and (c) some colubrid snakes of the genus Ninia present a conspicuous resistance to the toxic action of M. nigrocinctus venom.     

A new dwarf boa (Serpentes, Booidea, 'Tropidophiidae') from the Early Oligocene of Belgium: a case of the isolation of Western European snake faunas

Falseryx neervelpensis sp. nov. (Booid-grade, 'Tropidophiidae') from the earliest Oligocene (MP 21) of Belgium is described on the basis of vertebrae coming from all major portions of the vertebral column. In its peculiar caudal osteology, the snake approaches the unique morphological pattern characteristic of the living Neotropical Tropidophiinae. This is the first time such a complete and informative vertebral column of a dwarf boa has been described. The genus Falseryx was absent from Western Europe in younger parts of the Oligocene, but reappeared at the end of the Early Miocene. This dispersal pattern provides additional evidence that in most phases of the Oligocene and Early Miocene Western European snake faunas were effectively isolated from possible influences from the East.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 393–406.     

Head shape allometry and proximate causes of head sexual dimorphism in Podarcis lizards: joining linear and geometric morphometrics

Podarcis bocagei and Podarcis carbonelli are two lacertid species endemic to the western Iberian Peninsula, and both show head size and shape sexual dimorphism. We studied immature and adult head sexual dimorphism and analysed ontogenetic trajectories of head traits with body and head size, aiming to shed light on the proximate mechanisms involved. Immatures were much less dimorphic than adults, but geometric morphometric techniques revealed that head shape sexual differences are already present at this stage. Males and females differed in allometry of all head characters with body size, with males showing a disproportionate increase of head size and dimensions. On the other hand, head dimensions and head shape changed with increasing head size following similar trends in both sexes, possibly indicating developmental restrictions. Consequently, adult sexual dimorphism for head characters in these species is the result of both shape differences in the immature stage and hypermetric growth of the head in relation to body size in males.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 111–124.     

The origin of snakes (Serpentes) as seen through eye anatomy

Snakes evolved from lizards but have dramatically different eyes. These differences are cited widely as compelling evidence that snakes had fossorial and nocturnal ancestors. Their eyes, however, also exhibit similarities to those of aquatic vertebrates. We used a comparative analysis of ophthalmic data among vertebrate taxa to evaluate alternative hypotheses concerning the ecological origin of the distinctive features of the eyes of snakes. In parsimony and phenetic analyses, eye and orbital characters retrieved groupings more consistent with ecological adaptation rather than accepted phylogenetic relationships. Fossorial lizards and mammals cluster together, whereas snakes are widely separated from these taxa and instead cluster with primitively aquatic vertebrates. This indicates that the eyes of snakes most closely resemble those of aquatic vertebrates, and suggests that the early evolution of snakes occurred in aquatic environments.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 81 , 469–482.     

Sex-specific niche partitioning and sexual size dimorphism in Australian pythons (Morelia spilota imbricata)

Sexual dimorphism is usually interpreted in terms of reproductive adaptations, but the degree of sex divergence also may be affected by sex-based niche partitioning. In gape-limited animals like snakes, the degree of sexual dimorphism in body size (SSD) or relative head size can determine the size spectrum of ingestible prey for each sex. Our studies of one mainland and four insular Western Australian populations of carpet pythons ( Morelia spilota ) reveal remarkable geographical variation in SSD, associated with differences in prey resources available to the snakes. In all five populations, females grew larger than males and had larger heads relative to body length. However, the populations differed in mean body sizes and relative head sizes, as well as in the degree of sexual dimorphism in these traits. Adult males and females also diverged strongly in dietary composition: males consumed small prey (lizards, mice and small birds), while females took larger mammals such as possums and wallabies. Geographic differences in the availability of large mammalian prey were linked to differences in mean adult body sizes of females (the larger sex) and thus contributed to sex-based resource partitioning. For example, in one population adult male snakes ate mice and adult females ate wallabies; in another, birds and lizards were important prey types for both sexes. Thus, the high degree of geographical variation among python populations in sexually dimorphic aspects of body size and shape plausibly results from geographical variation in prey availability.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 113–125.     

Morphological and ecological convergence in two natricine snakes

Similar morphologies between species may be due to shared ancestry or convergent evolution . Understanding instances of morphological and ecological convergence is central to evolutionary ecology because they help us understand the fit between organism and environment. Two species of stream-dwelling natricine snakes, Thamnophis rufipunctatus and Nerodia harteri present a model system for studying ecological and morphological convergence and adaptation. The species are allopatric and both live in shallow riffles in streams and forage visually for fish. We studied morphological similarity, trait evolution and functional significance of ecologically relevant traits in these and related species, and used mitochondrial DNA sequences for the ND4 gene to estimate their phylogenetic relationships. Character mapping of head length and head width supported the hypothesis of independent evolution of head shape in T .  rufipunctatus and N .  harteri . The elongate snout is a derived trait in these two taxa that is associated with reduced hydrodynamic drag on the snakes' heads when in a swift current, compared to other species with the ancestral blunt snout. We hypothesize that lower hydrodynamic drag facilitates prey capture success in these species that are known to forage by holding their position in currents and striking at fish prey. The elongate snout morphology has also resulted in a diminished binocular vision field in these snakes, contrary to the hypothesis that visually orientated snakes should exhibit relatively greater binocular vision. Convergent evolution of the long snout and reduced hydrodynamic drag in T. rufipunctatus and N. harteri are consistent with the hypothesis that the long snout is an adaptation to foraging in a swift current.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 363–371.     

Phenotypic divergence between seasnake (Emydocephalus annulatus) populations from adjacent bays of the New Caledonian Lagoon

Populations of widespread species often differ in phenotypic traits, although rarely in such a dramatic fashion as revealed by research on turtle‐headed seasnakes (Emydocephalus annulatus). These snakes are highly philopatric, with mark–recapture studies showing that the interchange of individuals rarely occurs even between two adjacent bays (separated by < 1.2 km) in Noumea, New Caledonia. Data on > 500 field‐captured snakes from these two bays reveal significant differences between these two locations in snake morphology (mean body length, relative tail length, head shape), colour, ecology (body condition, growth rate, incidence of algal fouling), behaviour (antipredator tactics), and locomotor performance. For some traits, the disparity was very marked (e.g. mean swimming speeds differed by > 30%). The causal bases for these phenotypic divergences may involve founder effects, local adaptation, and phenotypic plasticity. The spatial divergence in phenotypic traits offers a cautionary tale both for researchers (sampling of only a few populations may fail to provide a valid overview of the morphology, performance, and behaviour of a species) and managers (loss of local populations may eliminate distinctive genetic variation). © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

Thermoregulation during gravidity in the children's python (Antaresia childreni): a test of the preadaptation hypothesis for maternal thermophily in snakes

Pregnant squamate reptiles (i.e. lizards and snakes) often maintain higher and more stable body temperatures than their nonpregnant conspecifics, and this maternal thermophily enhances developmental rate and can lead to increased offspring quality. However, it is unclear when this behaviour evolved relative to the evolution of viviparity. A preadaptation hypothesis suggests that maternal thermophily was a preadaptation to viviparity. Oviparous squamates are unique among oviparous reptiles for generally retaining their eggs until the embryos achieve one fourth of their development. As a result, maternal thermophily by gravid squamates may provide the same thermoregulatory benefits, at least during early development, that have been associated with viviparity. Thus, the evolution of viviparity in squamates may reflect an expanded duration of a pre-existing maternal thermoregulatory behaviour. Despite its evolutionary relevance, thermoregulation during gravidity in oviparous squamates has not yet been explored in depth. In the present study, we examined whether gravidity was associated with thermoregulatory changes in the oviparous children's python, Antaresia childreni . First, we discovered that, compared to most snakes, A. childreni is at an advanced stage of embryonic development at oviposition. Second, using surgically implanted temperature loggers, we detected a significant influence of reproductive status on thermoregulation. Reproductive females maintained higher and less variable body temperatures than nonreproductive females and this difference was most pronounced during the last 3 weeks of gravidity. Overall, these results highlight the continuum between oviparity and viviparity in squamate reptiles and emphasize the importance of thermal control of early embryonic development independent of reproductive mode.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 499–508.     

Dangerous food: lacking venom and constriction,how do snake‐like lizards (Lialis burtonis,Pygopodidae) subdue their lizard prey?

Snakes are renowned for their ability to subdue and swallow large, often dangerous prey animals. Numerous adaptations, including constriction, venom, and a strike-and-release feeding strategy, help them avoid injury during predatory encounters. Burton's legless lizard ( Lialis burtonis Gray, Pygopodidae) has converged strongly on snakes. It is functionally limbless and feeds at infrequent intervals on relatively large prey items (other lizards) capable of inflicting a damaging bite. However, L. burtonis possesses neither venom glands, nor the ability to constrict prey. We investigated how L. burtonis subdues its prey without suffering serious retaliatory bites. Experiments showed that lizards modified their strike precision according to prey size; very large prey were always struck on the head or neck, preventing them from biting. In addition, L. burtonis delayed swallowing large lizards until they were incapacitated, whereas smaller prey were usually swallowed while still struggling. Lialis burtonis also displays morphological adaptations protecting it from prey retaliation. Its long snout prevents prey from biting, and it can retract its lidless eyes out of harm's way while holding onto a food item. The present study further clarifies the remarkable convergence between snakes and L. burtonis , and highlights the importance of prey retaliatory potential in predator evolution.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91 , 719–727.     

Convergent body flattening in a clade of tropical rock-using lizards (Scincidae: Lygosominae)

The repeated occurrence of similar morphologies in organisms from similar habitats provides good evidence of convergent selection, and convergent patterns of evolutionary change. In lizards, a flattened morphology has often been noted; however, whether this trait is convergent in specific habitats has never been tested using phylogenetic methods. The present study examined patterns of morphological convergence in 18 species of tropical Lygosomine skinks from three broad habitat categories (generalist, leaf litter-dwelling, and rock-using species). In general, although there where relatively few morphological differences of species from different habitats, phylogenetic analyses revealed that rock-using species have consistently and repeatedly evolved a dorsoventrally flattened head and body. The adaptive basis of this flattened morphology is consistent with both biomechanical predictions of performance (e.g. climbing locomotion) and ecology (e.g. use of rock crevices, camouflage) of species that occupy rocky habitats.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 399–411.     

Trade‐offs between eating and moving: what happens to the locomotion of slender arboreal snakes when they eat big prey?

The capacity to consume large prey evolved long ago in snakes. Subsequently, many specialized arboreal snake species convergently evolved slender bodies, presumably well‐suited for moving on thin branches and steep slopes, although how this accentuates changes in their shape and weight after eating and creates trade‐offs with locomotor performance is poorly understood. Hence, we tested whether the performance and modes of locomotion of a specialized arboreal snake (Boiga irregularis) changed after eating one or two mice when crawling on cylinders with and without pegs and on horizontal or 45° slopes. On surfaces with pegs: (1) only lateral undulation was used; (2) speed decreased with increased meal size; and (3) unexpectedly, more sideways toppling occurred than without pegs. On the horizontal cylinders without pegs, most unfed snakes used lateral undulation with continuous sliding contact, whereas, after eating two mice, most snakes periodically stopped and gripped the cylinder with speeds of concertina locomotion similar to those for the lateral undulation of unfed snakes. Thus, the behaviour of switching to a gripping mode of locomotion (concertina) circumvented some of the constraints of a slender limbless body plan, for which bulky meals alter shape and can impede the movement of the propulsive structures. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 446–458.