Visceral pentastomiasis caused by Armillifer armillatus in a captive striped hyena (Hyaena hyaena) in Chiang Mai Night Safari,Thailand

Visceral pentastomiasis (porocephalosis) caused by Armillifer armillatus larvae was incidentally diagnosed in a female striped hyena (Hyaena hyaena) of unknown age which died unexpectedly in 2013. The hyena had been imported from Tanzania 8 years earlier and have been since then in a zoo in Chiang Mai, northern Thailand. Pathological examination revealed visceral nymph migrans of pentastomes throughout the intestine, liver, diaphragm, omentum and mesentery, spleen, kidneys, and urinary bladder. Polymerase chain reaction and sequencing that targeted the pentastomid-specific 18S rRNA gene determined 100% identity with reference sequence for A. armillatus, suggesting that its ova can infect the hyena to serve as an intermediate host for the parasite. Further studies to identify the source of infection, its risk factors, and host range for A. armillatus are important to determine its zoonotic potential and to better prevent and manage the disease to protect animal and human health.     

<Emphasis Type="Italic">Armillifer</Emphasis>-Infected Snakes Sold at Congolese Bushmeat Markets Represent an Emerging Zoonotic Threat

African pythons (Pythonidae) and large vipers (Bitis spp.) act as definitive hosts for Armillifer armillatus and Armillifer grandis parasites (Crustacea: Pentastomida) in the Congo Basin. Since the proportion of snakes in bushmeat gradually increases, human pentastomiasis is an emerging zoonotic disease. To substantiate the significance of this threat, we surveyed snakes offered for human consumption at bushmeat markets in the Kole district, Democratic Republic of the Congo, for the presence of adult pentastomids. In Bitis vipers (n = 40), Armillifer spp. infestations exhibited an 87.5% prevalence and 6.0 median intensity. Parasite abundance covaried positively with viper length, but not with body mass. In pythons (n = 13), Armillifer spp. exhibited a 92.3% prevalence and 3.5 median intensity. The positive correlations between parasite abundance and python length or mass were statistically nonsignificant. Ninety-one percent of A. grandis were discovered in vipers and 97% of infected vipers hosted A. grandis, whereas 81% of A. armillatus specimens were found in pythons and 63% of infected pythons hosted A. armillatus. Thus, challenging the widespread notion of strict host specificity, we found ‘reversed’ infections and even a case of coinfection. In this study, we also gathered information about the snake consumption habits of different tribal cultures in the area. Infective parasite ova likely transmit to humans directly by consumption of uncooked meat, or indirectly through contaminated hands, kitchen tools or washing water.     

Multi-host Model-Based Identification of Armillifer agkistrodontis (Pentastomida), a New Zoonotic Parasite from China

Background

Pentastomiasis is a rare parasitic infection of humans. Pentastomids are dioecious obligate parasites requiring multiple hosts to complete their lifecycle. Despite their worm-like appearance, they are commonly placed into a separate sub-class of the subphylum Crustacea, phylum Arthropoda. However, their systematic position is not uncontested and historically, they have been considered as a separate phylum.

Methodology/Principal Findings

An appraisal of Armillifer agkistrodontis was performed in terms of morphology and genetic identification after its lifecycle had been established in a multi-host model, i.e., mice and rats as intermediate hosts, and snakes (Agkistrodon acutus and Python molurus) as definitive hosts. Different stages of the parasite, including eggs, larvae and adults, were isolated and examined morphologically using light and electron microscopes. Phylogenetic and cluster analysis were also undertaken, focusing on the 18S rRNA and the Cox1 gene. The time for lifecycle completion was about 14 months, including 4 months for the development of eggs to infectious larvae in the intermediate host and 10 months for infectious larvae to mature in the final host. The main morphological difference between A. armillatus and Linguatula serrata is the number of abdominal annuli. Based on the 18S rRNA sequence, the shortest hereditary distance was found between A. agkistrodontis and Raillietiella spp. The highest degree of homology in the Cox 1 nucleic acid sequences and predicted amino acid sequences was found between A. agkistrodontis and A. armillatus.

Conclusion

This is the first time that a multi-host model of the entire lifecycle of A. agkistrodontis has been established. Morphologic and genetic analyses supported the notion that pentastomids should be placed into the phylum Arthropoda.     

Diagnosis of Human Visceral Pentastomiasis

Visceral pentastomiasis in humans is caused by the larval stages (nymphs) of the arthropod-related tongue worms Linguatula serrata, Armillifer armillatus, A. moniliformis, A. grandis, and Porocephalus crotali. The majority of cases has been reported from Africa, Malaysia, and the Middle East, where visceral pentastomiasis may be an incidental finding in autopsies, and less often from China and Latin America. In Europe and North America, the disease is only rarely encountered in immigrants and long-term travelers, and the parasitic lesions may be confused with malignancies, leading to a delay in the correct diagnosis. Since clinical symptoms are variable and serological tests are not readily available, the diagnosis often relies on histopathological examinations. This laboratory symposium focuses on the diagnosis of this unusual parasitic disease and presents its risk factors and epidemiology.     

Morphology,Reproduction and Diet in Australian and Papuan Death Adders (Acanthophis,Elapidae)

Death adders (genus Acanthophis) differ from most other elapid snakes, and resemble many viperid snakes, in their thickset morphology and ambush foraging mode. Although these snakes are widely distributed through Australia and Papua New Guinea, their basic biology remains poorly known. We report morphological and ecological data based upon dissection of >750 museum specimens drawn from most of the range of the genus. Female death adders grow larger than conspecific males, to about the same extent in all taxa (20% in mean adult snout-vent length,  =  SVL). Most museum specimens were adult rather than juvenile animals, and adult males outnumbered females in all taxa except A. pyrrhus. Females have shorter tails (relative to SVL) than males, and longer narrower heads (relative to head length) in some but not all species. The southern A. antarcticus is wider-bodied (relative to SVL) than the other Australian species. Fecundity of these viviparous snakes was similar among taxa (mean litter sizes 8 to 14). Death adders encompass a broad range of ecological attributes, taking a wide variety of vertebrate prey, mostly lizards (55%), frogs and mammals (each 21%; based on 217 records). Dietary composition differed among species (e.g. frogs were more common in tropical than temperate-zone species), and shifted with snake body size (endotherms were taken by larger snakes) and sex (male death adders took more lizards than did females). Overall, death adders take a broader array of prey types, including active fast-moving taxa such as endotherms and large diurnal skinks, than do most other Australian elapids of similar body sizes. Ambush foraging is the key to capturing such elusive prey.     

Predation upon Hatchling Dinosaurs by a New Snake from the Late Cretaceous of India

Derived large-mouthed snakes (macrostomatans) possess numerous specializations in their skull and lower jaws that allow them to consume large vertebrate prey. In contrast, basal snakes lack these adaptations and feed primarily on small prey items. The sequence of osteological and behavioral modifications involved in the evolution of the macrostomatan condition has remained an open question because of disagreement about the origin and interrelationships of snakes, the paucity of well-preserved early snake fossils on many continental landmasses, and the lack of information about the feeding ecology of early snakes. We report on a partial skeleton of a new 3.5-m-long snake, Sanajeh indicus gen. et sp. nov., recovered from Upper Cretaceous rocks of western India. S. indicus was fossilized in association with a sauropod dinosaur egg clutch, coiled around an egg and adjacent to the remains of a ca. 0.5-m-long hatchling. Multiple snake-egg associations at the site strongly suggest that S. indicus frequented nesting grounds and preyed on hatchling sauropods. We interpret this pattern as “ethofossil” preservation of feeding behavior. S. indicus lacks specializations of modern egg-eaters and of macrostomatans, and skull and vertebral synapomorphies place it in an intermediate position in snake phylogeny. Sanajeh and its large-bodied madtsoiid sister taxa Yurlunggur camfieldensis and Wonambi naracoortensis from the Neogene of Australia show specializations for intraoral prey transport but lack the adaptations for wide gape that characterize living macrostomatan snakes. The Dholi Dungri fossils are the second definitive association between sauropod eggs and embryonic or hatchling remains. New fossils from western India provide direct evidence of feeding ecology in a Mesozoic snake and demonstrate predation risks for hatchling sauropod dinosaurs. Our results suggest that large body size and jaw mobility afforded some non-macrostomatan snakes a greater diversity of prey items than previously suspected on the basis of extant basal snakes.     

Thermal correlates of foraging-site selection by Chinese pit-vipers (Gloydius shedaoensis,Viperidae)

• 1.Do thermal factors influence foraging-site selection by ectothermic predators? Snake species that obtain their prey from ambush must remain immobile for long periods, precluding overt behavioural thermoregulation; and some “ambush” snakes use thermal cues to detect endothermic prey. Plausibly, alternative ambush sites might differ either in equilibrial body temperatures available to snakes, or in the thermal “background” against which prey items must be detected.
• 2.We examined this topic with field data on pit-vipers (Gloydius shedaoensis) on a small island in northeastern China. Adult snakes feed only on migrating passerine birds. The snakes ambush birds both from arboreal perches (branches of small trees) and from the ground.
• 3.Arboreal versus terrestrial ambush sites differed both in operative temperatures and thermal “backgrounds” available to the snakes. Operative temperatures inside copper models were lower in trees than on the ground (because of wind), and snakes in arboreal ambush sites were cooler than those in terrestrial sites. Thermal backgrounds from arboreal perches were cooler (and thus, provided more contrast against prey items) than did backgrounds available from terrestrial ambush-sites.
• 4.Thermal factors thus modify the suitability of alternative ambush locations for these pit-vipers, but with a trade-off: a snake in a tree can “see” its prey more clearly, but may not be warm enough (and hence, able to strike fast enough) to capture it. Further work is required to determine whether or not snakes actually use such thermal differences as criteria for the selection of ambush sites.

     

An exotic species is the favorite prey of a native enemy

Although native enemies in an exotic species'' new range are considered to affect its ability to invade, few studies have evaluated predation pressures from native enemies on exotic species in their new range. The exotic prey naiveté hypothesis (EPNH) states that exotic species may be at a disadvantage because of its naïveté towards native enemies and, therefore, may suffer higher predation pressures from the enemy than native prey species. Corollaries of this hypothesis include the native enemy preferring exotic species over native species and the diet of the enemy being influenced by the abundance of the exotic species. We comprehensively tested this hypothesis using introduced North American bullfrogs (Lithobates catesbeianus, referred to as bullfrog), a native red-banded snake (Dinodon rufozonatum, the enemy) and four native anuran species in permanent still water bodies as a model system in Daishan, China. We investigated reciprocal recognition between snakes and anuran species (bullfrogs and three common native species) and the diet preference of the snakes for bullfrogs and the three species in laboratory experiments, and the diet preference and bullfrog density in the wild. Bullfrogs are naive to the snakes, but the native anurans are not. However, the snakes can identify bullfrogs as prey, and in fact, prefer bullfrogs over the native anurans in manipulative experiments with and without a control for body size and in the wild, indicating that bullfrogs are subjected to higher predation pressures from the snakes than the native species. The proportion of bullfrogs in the snakes'' diet is positively correlated with the abundance of bullfrogs in the wild. Our results provide strong evidence for the EPNH. The results highlight the biological resistance of native enemies to naïve exotic species.     

Toxic,invasive treefrog creates evolutionary trap for native gartersnakes

Possession of unique defensive toxins by nonindigenous species may increase the likelihood of creating evolutionary traps for native predators. We tested the hypothesis that nonindigenous, toxic Cuban Treefrogs (Osteopilus septentrionalis) have created an evolutionary trap for native, generalist snakes. Additionally, we explored the possibility that populations of snakes that co-occur with Cuban Treefrogs have responded in ways that allow them to escape potential trap dynamics. To evaluate a potential fitness cost of consuming Cuban Treefrogs, we monitored growth of 61 wild-caught Common Gartersnakes (Thamnophis sirtalis) fed exclusive diets of either Cuban Treefrogs, native Green Treefrogs (Hyla cinerea), or native Golden Shiners (Notemigonus crysoleucas). Snakes in the Cuban Treefrog diet treatment gained less than half the mass of those consuming native prey, and Cuban Treefrogs were significantly less digestible than native prey. There was no difference in the response of gartersnakes to prey scent cues of Cuban Treefrogs and Green Treefrogs. Our results indicate that Cuban Treefrogs likely represent an evolutionary trap for snakes because consumption of these frogs carries fitness costs, yet snakes fail to recognize this prey as being costly. We found no difference in growth or response to prey cues between snakes from invaded and non-invaded regions, suggesting snakes have not responded to escape trap dynamics. Interactions of native snakes and Cuban Treefrogs support the idea that introduced species with novel toxins may increase the likelihood of evolutionary trap formation.     

Sexual differences in morphology and niche utilization in an aquatic snake,Acrochordus arafurae

Filesnakes (Acrochordus arafurae) are large (to 2 m), heavy-bodied snakes of tropical Australia. Sexual dimorphism is evident in adult body sizes, weight/length ratios, and body proportions (relative head and tail lengths). Dimorphism is present even in neonates. Two hypotheses for the evolution of such dimorphism are (1) sexual selection or (2) adaptation of the sexes to different ecological niches. The hypothesis of sexual selection is consistent with general trends of sexually dimorphic body sizes in snakes, and accurately predicts, for A. arafurae, that the larger sex (female) is the one in which reproductive success increases most strongly with increasing body size. However, the sexual dimorphism in relative head sizes is not explicable by sexual selection.The hypothesis of adaptation to sex-specific niches predicts differences in habitats and/or prey. I observed major differences between male and female A. arafurae in prey types, prey sizes and habitat utilization (shallow versus deep water). Hence, the sexual dimorphism in relative head sizes is attributed to ecological causes rather than sexual selection. Nonetheless, competition between the sexes need not be invoked as the selective advantage of this character divergence. It is more parsimonious to interpret these differences as independent adaptations of each sex to increase foraging success, given pre-existing sexually-selected differences in size, habitat or behavior. Data for three other aquatic snake species, from phylogenetically distant taxa, suggest that sexual dimorphism in food habits, foraging sites and feeding morphology, is widespread in snakes.     

Size-dependent predation by snakes: selective foraging or differential prey vulnerability?

I staged replicate encounters between unrestrained lizards andsnakes in outdoor enclosures to examine size-dependent predationwithin the common garden skink (Lampropholis guichenoti). Yellow-facedwhip snakes (Demansia psammophis) forage widely for activeprey and most often consumed large skinks, whereas death adders(Acanthophis antarcticus) ambush active prey and most oftenconsumed small skinks. Small-eyed snakes (Rhinoplocephalusnigrescens) forage widely for inactive prey and consumed bothsmall and large skinks equally often. Differential predationmay reflect active choice by the predator, differential preyvulnerability, or both. To test for active choice, I presentedforaging snakes with an inert small lizard versus an inertlarge lizard. They did not actively select lizards of a particularbody size. To test for differential prey vulnerability, I quantifiedvariation between small and large lizards in behavior thatis important for determining the outcome of predator—prey interactions. Snakes did not differentiate between integumentarychemicals from small and large lizards. Large lizards tendto flee from approaching predators, thereby eliciting attackby the visually oriented whip snakes. Small lizards were moremobile than large lizards and therefore more likely to passby sedentary death adders. Additionally, small skinks were more effectively lured by this sit-and-wait species and less likelyto avoid its first capture attempt. In contrast, overnightretreat site selection (not body size) determined a lizard'schances of being detected by small-eyed snakes. Patterns ofsize-dependent predation by elapid snakes may arise not becauseof active choice but as a function of species-specific predatortactics and prey behavior.     

Size, Sex And Geographic Variation in the Diet of the Tiger Shark, Galeocerdo Cuvier, From Western Australian Waters

Stomach contents from tiger sharks, Galeocerdo cuvier, caught on lines off the central coast of Western Australia were analysed to investigate variations in the diet due to sex, size and geographic location. Stomachs from 84 specimens contained food, while 26 had empty stomachs and 66 had regurgitated. Twelve prey groups were identified, the most common being turtles, sea snakes, teleost fishes, dugongs and sea birds. Dietary overlap was high between males and females. An ontogenetic shift was observed in the diet. Smaller prey (e.g. cephalopods, teleosts and sea snakes) were more common in small individuals, while the occurrence of larger prey (e.g. turtles, dugongs and elasmobranchs) increased with increasing shark size. Differences in the diet were observed between four regions along the central Western Australian coast. The ability to catch and consume large prey, prey availability, prey density, and prey profitability were identified as factors influencing the diet. The high level of occurrence of dugongs and turtles in the diet of G. cuvier, relative to their abundance, suggests that shark predation may play an important role in regulating populations of these species.     

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

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

Duration of strike-induced chemosensory searching in long-term captive rattlesnakes at national zoo,audubon zoo,and San Diego Zoo

Rattlesnakes typically strike and release adult rodent prey. Striking is followed by a sustained, high rate of tongue flicking that guides the snake to the envenomated, dead prey. Wild-caught rattlesnakes exhibited this chemosensory searching for about 2.5 h, and the present study demonstrated that long-term captive rattlesnakes (Crotalus atrox, C durissus, C horridus, C vegrandis, C unicolor) at three zoos did the same. Because these zoo-raised snakes had always been offered dead rodents and because the snakes had become accustomed to ingesting them without striking, the present snakes had rarely exercised their innate predatory repertoires. The duration of chemosensory searching in these snakes indicates that this important aspect of the predatory repertoire had not been degraded as a consequence of long-term captive husbandry.     

The role of vision in the predatory behaviour of natricine snakes

Early workers concluded that ingestively naive garter snakes (Thamnophis) recognize chemical cues from their normal prey, and that such cues are sufficient to elicit prey attack, whereas visual prey cues are not sufficient. In the light of recent observations on how garter and water snakes (Nerodia) forage, new tests were made of the role of visual stimuli in the aquatic predation of several natricine species. Both experienced and ingestively naive snakes oriented to and attacked a fish model in plain water, although they made more orientations and attacks when diffuse fish odour was present in the water. Fish odour in water also elicited increased aquatic searching behaviour. Early views on the role of vision in the predation of newborn natricine snakes require modification, and there is a need for investigation of the properties of effective visual stimuli and the ontogeny of responsiveness to them.     

Meal Size Effects on Antipredator Behavior of Hatchling Trinket Snakes, Elaphe helena

Current foraging models limit the decision‐making process of animals to the food searching and consuming phase. The post‐consummatory phase of feeding may influence optimal meal size for some species as a morphologic change often results from feeding. In snakes, a single prey item can lead to abrupt increases in body mass, thus influencing locomotor performance. Identifying factors affecting locomotor performance can help predict behaviors that should maximize an animal's chance of evading predators. Although many snakes ingest large percentages of their body mass, not much work has examined the post‐consummatory effects of ingesting bulky prey differing in relative mass. I examined the locomotor performance and antipredator tactics of hatchling trinket snakes (Elaphe helena) after subjecting snakes to mice prey varying by relative mass differences of 20–35%, 50–59% or 70–79% of an individual hatchling's body mass. Snakes in treatment groups were compared with snakes in a control group (0%). Meal size‐affected locomotor parameters such as burst speed, endurance, and endurance times for hatchlings that ingested 50–59% and 70–79% of their body mass (p < 0.001). Recent feeding also affected the types of antipredator modes employed. Hatchlings in the 0% and 20–35% treatments exhibited behaviors that were categorized as active and threatening, while hatchlings in the 50–59% and 70–79% treatments exhibited stationary, neutral, and cryptic behaviors. Although snakes may become more reclusive following a meal, this study demonstrates that relative prey mass affects the ability of hatchling trinket snakes to flee from a predator. In turn, these results suggest that the post‐consummatory effects of foraging should be considered in optimal foraging models for organisms that consume a substantial portion of their body mass during a single feeding.     

Childhood pentastomiasis: A report of three cases with the following-up data

Pentastomiasis, a zoonotic parasitic disease, has been reported commonly in Africa and Asia. It is caused by pentastomes, which are annulated but unsegmented blood-sucking endoparasites. Fewer than 20 cases have been reported during the past two decades in China, and cases in children have been especially rare. Herein, we report three cases of pediatric patients with severe systemic symptoms, focusing on the clinical features, diagnosis, and therapy of this disease. The patients were two boys and one girl aged 3 to 13 years. They all had a history of snake or worm ingested from snake and initial symptoms of fever, abdominal pain, diarrhea, and weight loss. Eosinophilia, anemia and elevated serum IgE levels were noted. Moreover, the large numbers of nodules, or even calcification, in the liver and/or lungs were noted by ultrasound, CT or MRI scans. These pentastomes were identified as Armillifer moniliformis, Porocephalus taiwana and Armillifer agkistrodontis. Praziquantel and mebendazole deworming treatments were adopted for the patients. Hence, pentastomiasis should be considered in the differential diagnosis for patients with multiple organ or system lesions, especially abdominal signs, that develop after the ingestion of snakes. Ultrasound, CT and MRI scans and laparoscopic approaches might be helpful for the diagnosis.     

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.     

Why do Juvenile Chinese Pit‐Vipers (Gloydius shedaoensis) Select Arboreal Ambush Sites?

Ontogenetic shifts in habitat use are widespread, especially in ectothermic taxa in which juveniles may be an order of magnitude smaller than large adult conspecifics. The factors that generate such habitat shifts are generally obscure, but we studied an unusual system that allowed us to compare consequences of habitat selection between adults and juveniles. Pit‐vipers (Gloydius shedaoensis) on a small island in north‐eastern China feed almost entirely on seasonally migrating birds. During the spring bird‐migration period, individual snakes consistently re‐used either arboreal or terrestrial ambush sites. Snakes in trees were smaller (and more philopatric) than snakes on the ground. This ontogenetic shift in habitat use may reflect the difficulty of capturing birds on the ground, especially by small snakes. In laboratory trials, large (adult) pit‐vipers struck faster, further and more accurately than did small (juvenile) snakes. In experiments with free‐ranging snakes, the proportion of strikes hitting the bird was lower for juveniles than for adults, and lower for terrestrial snakes than for arboreal snakes. Additionally, adult snakes generally seized the bird by the head whereas juveniles frequently struck the body or wings (and thus, obtained a less secure grip). Arboreal ambush sites may facilitate prey capture not only because they give access to smaller birds but also because they render the bird's location more predictable and, hence, enable the snake to position itself optimally prior to the prey's arrival. Because juvenile pit‐vipers are less capable strikers, and are small relative to available prey items, they may benefit from the greater ease of prey capture from branches. Thus, the ontogenetic shift in habitat selection within this species may be because of ontogenetic shifts in the vipers’ ability to capture and ingest large, mobile prey.     

Strike-induced chemosensory searching in old world vipers and new world pit vipers at San Diego Zoo

Rattlesnakes (Crotalus unicolor, C vegrandis) and Russell's vipers (Vipera russelli) at San Diego Zoo exhibited sustained high rates of tongue flicking after striking mice (Mus musculus) but not after seeing, smelling, and/or detecting thermal cues arising from mice. Called strike-induced chemosensory searching (SICS), this phenomenon contributes to poststrike trailing of envenomated prey. Because these zoo-raised snakes had always been offered dead rodents, and because these prey were usually ingested without first being struck, the present snakes had rarely exercised their innate predatory repertoire (ie, ambush tactics including striking, releasing, and trailing). Indeed, most specimens had never before struck a mouse and, hence, had never exhibited SICS. The occurrence of SICS in the present study clearly indicates that this important aspect of the predatory repertoire had not been degraded as a consequence of long-term captive husbandry.