Despite numerous studies aimed at resolving relationships among basal euteleost lineages, many aspects of their phylogeny remain the subject of debate. The Esociformes have proven particularly difficult to place, and although a hypothesis of relationships within this group first proposed by Nelson has been generally accepted, a recent hypothesis based on evidence from mitochondrial DNA sequences is not congruent with it. We have assembled an expanded dataset of DNA sequences from the mitochondrial and nuclear genomes to test existing hypotheses of esociform inter- and intraordinal relationships. This dataset includes representatives from all extant esociform lineages and a wide diversity of potential outgroups (51 taxa in total). We also conducted a review of the morphological information that supports currently held hypotheses of esociform inter- and intraordinal relationships. This review revealed potential problems with character state coding and interpretation of character states. However, the molecular evidence, particularly the nuclear sequences, produced unambiguous support for a sister-group relationship between esociforms and salmonoids and also offer similarly strong corroboration of the hypothesis of esociform intraordinal relationships based on mitochondrial sequences and for the monophyly of the subgenera Esox and Kenoza of Esox. In addition to the conclusions regarding esociform relationships, the molecular evidence we present offers support for the monophyly of the Osmeridae, for a sister-group relationship between the Retropinnidae and the Osmeroidei (Osmeridae Salangidae Plecoglossidae) and for a close relationship of Stomiiformes and Osmeriformes.

A six-year mark-recapture study, consisting of 567 captures of 216 individually marked snakes, and the birth of 889 young in 53 litters born to 39 wild-caught females were used to estimate demographic and life-history parameters of a Northern Illinois population of Thamnophis radix. Using the von Bertalanffy growth model, males were found to differ from females in asymptotic size but not in the rate at which they approached this size. Size of known age individuals together with growth rate estimates were used to assign age at first capture. Age and sex were then used as grouping variables to obtain age- and sex-specific survival using program MARK. The results suggest that males and females have approximately equal survival in the 0 and 1 age classes but that females have higher survival than males as adults (0.45 vs 0.35). Population estimates calculated using Schumacher-Eschmeyer and Jolly-Seber methods indicate an adult population size of 64 and 172 adults, respectively, corresponding to densities of 40 and 107 adults per hectare. Average female fertility increased from 6.4 in one-year-old females to 21 among six-year-old females. Detailed demographic studies such as this have utility in development of management strategies and theories concerning life-history evolution.

Photophase and illumination affect many fish activities. In this study, we examined their effects on the critical swimming velocities (Ucrit), swimming gait patterns, and oral grasping behavior of five California estuarine fishes. All species (4–5 cm SL) swam similarly (mean U_crit range: 30–36 cm/sec) under day/light conditions. However, both nighttime photophase and darkness decreased Delta Smelt (Hypomesus transpacificus) swimming velocities. Congeneric Wakasagi (Hypomesus nipponensis) swimming performance also decreased at night/dark conditions. Regardless of photophase and illumination, Delta Smelt, Wakasagi, and Splittail (Pogonichthys macrolepidotus) exhibited three swimming gaits: intermittent stroke-and-glide at low velocities, continuous stroking at moderate velocities, and intermittent burst-and-glide at high velocities near Ucrit. In contrast, Chinook Salmon (Onchorhynchus tshawytscha) used only two swimming gaits: continuous stroking and burst-and-glide under all conditions. Inland Silversides (Menidia beryllina) used these two gaits under light conditions and all three gaits under dark conditions. Some Wakasagi, Splittail, and Chinook Salmon orally grasped the upstream screen in the flume at moderate to high water velocities. Oral grasping does not require jaw teeth and may represent adaptive behavior in natural habitats. Regarding vulnerability to water diversions that operate in the dark at night, the threatened Delta Smelt and introduced Wakasagi, comparatively, may be more at risk than the other species.

Aggressive interference can be an important expression of competitive interactions within and among species. We studied potential interference between two similar-sized, sympatric species of woodland salamander. The Pigeon Mountain Salamander, Plethodon petraeus, occurs in habitat patches of rocky outcroppings along a restricted area on the eastern flank of Pigeon Mountain in northwestern Georgia. This species is relatively rare in the intervening areas of forest-floor habitat, which is occupied by a similar-sized, potential competitor, the Slimy Salamander (Plethodon glutinosus). Both species exhibited aggression and defended territories against conspecifics and heterospecifics in laboratory-based encounters. Individuals of P. glutinosus were superior in aggressive encounters with individuals of P. petraeus. Coexistence of the two species occurs because habitats are partially exclusive. There is enough habitat overlap, however, to generate possible interspecific competition. We hypothesize that the presence of territorial, aggressive P. glutinosus in areas between habitat patches may influence interpatch dispersal by P. petraeus.

Henochilus, a characiform genus endemic to eastern Brazil is reviewed. A single species, Henochilus wheatlandii, from the Rio Doce and possibly the Rio Mucuri in the states of Minas Gerais and Espirito Santo is recognized and redescribed. The phylogenetic analysis indicates that Henochilus is most closely related to the clade consisting of Brycon and likely Chilobrycon.

Three species of Microhyla from Indochina are described. One species is from the Northern Truong Son (Annamite Highlands) of Vietnam and Laos, characterized by finger I less than one-half the length of finger II; expanded disks at the tip of the digits with dorsal median longitudinal grooves producing the appearance of two scutes; two metatarsal tubercles; extensive webbing on feet: on toe IV web full to distal subarticular tubercle; and marbled belly. The second species is from the Tay Nguyen Plateau, Gia Lai Province, Vietnam. It is smaller than the above species, has full webbing to medial subarticular tubercle of toe IV, and has a dusted belly. Microhyla annamensis is discussed because of its similarity to the two new species above. A third species of Microhyla is described from Ngoc Linh Mountain in Quang Nam Province, Vietnam. It is easily separated from congeners of Indochina and China by its small size and the appearance of the first finger as a small, partially free nub. Microhyla palmipes is discussed because of its similarity to the third new species.

Gymnotus coatesi, a small and rare species of Neotropical electric fish, was originally described by LaMonte from material collected in Pará, Brazil, in 1934. The senior author discovered populations of this species in the vicinity of Tefé, Amazonas, Brazil, and near Iquitos and Jenaro Herrera in the lowland Upper Amazon of Peru. We provide a formal redescription of this species and describe external morphology, osteology, ecology, and electric signals, with emphasis on the Tefé population. Gymnotus coatesi can be distinguished from all congeners by a unique banding pattern and by a unique combination of morphometric and meristic characters. Gymnotus coatesi is known from localities along the main stem of the Amazon River from near the confluence of the Río Marañon with the Río Ucayali (Loreto, Peru) to the Rio Tocantins (Pará, Brazil) but is poorly represented in museum collections. In the Tefé region, G. coatesi inhabits the seasonally flooded lower courses of terra firme rain-forest streams. In the Peruvian Amazon, it also occurs in the upper, nonflooded, reaches of rainforest streams.

Two new species of the Hyla circumdata group are described from southeastern Brazil. The type localities of both species occur in the Atlantic Forest Domain. Hyla feioi sp. nov. is described from Serra do Ibitipoca, a regional designation within the Serra da Mantiqueira, and Hyla ahenea sp. nov. is described from Serra da Bocaina, a regional designation within the Serra do Mar. Descriptions of the tadpole, advertisement call, and information on natural history are provided for H. feioi sp. nov. The advertisement call of Hyla ibitipoca is described.

A new species of small-sized Scorpionfish, Scorpaenopsis insperatus, is described on the basis of two specimens collected from Chowder Bay, Sydney Harbour, New South Wales, Australia. The new species is distinguished from other species of Scorpaenopsis by the following combination of characters: a single upper opercular spine (tip not divided) and 30–34 longitudinal scale rows. Scorpaenopsis insperatus is the only member of the genus found in Australian temperate waters.

A new genus and species of the scorpaeniform family Liparidae, Lopholiparis flerxi, is described from the central Aleutian Islands, Alaska. The new genus differs from all known liparid genera in having supraorbital ridges, produced by enlarged and heavily ossified frontals and sphenotics, and enlarged opercles. It also has seven spinous dorsal-fin rays, the anteriormost six forming a distinct lobe; an elliptical pupil; and low dorsal- and anal-fin ray counts. It is most similar to Temnocora candida, which also possesses an anterior spinous dorsal-fin lobe and an elliptical pupil.

Icelinus limbaughi n. sp. is described from 36 specimens collected off the coast of California, from the Channel Islands, off San Diego, and on Cortez Bank, about 160 km off the coast of San Diego. It differs from all other species of Icelinus by the following combination of characters: a dorsal scale band that originates under the fourth to seventh dorsal-fin spine and terminates below the final or penultimate dorsal fin-ray, not extending onto caudal peduncle; absence of scales in the pectoral axilla; absence of cirri on dorsal-fin spines.

A new species of Pachycara is described from the Rainbow hydrothermal vent field (Mid-Atlantic Ridge, 36°13′N; 33°54′W). Pachycara saldanhai n. sp. is closely related to Pachycara thermophilum Geistdoerfer, 1994, from which it differs in having a lateral line with two branches, and a higher interorbital width to head length ratio, as well as higher vertebral, dorsal- and anal-fin rays counts.

A new killifish species, Rivulus duckensis, is described from the Reserva Adolpho Ducke, Manaus, Amazonas, Brazil. It is distinguished from other central Amazonian Rivulus species by maximum body size, adult color pattern, habitat preference and mitochondrial DNA sequences. Based on the phylogenetic analysis of molecular sequence data, our best hypothesis suggests that R. duckensis is sister taxon to a clade of Rivulus species occurring in the upper Río Orinoco basin, Amazonas state, Venezuela and Rivulus rectocaudatus, Amazonas department, Peru.

A new Knodus is described from the rio do Peixe, a tributary of the rio Cabaçal, in the upper portions of the rio Paraguay basin in Mato Grosso state, Brazil. It can be distinguished from its congeners, and in fact from all remaining characid fishes, by the presence of two symmetric, large dark blotches basally on caudal fin lobes. Comments on the disputed recognition of the genus Knodus are provided.

Neoetropus macrops Hildebrand and Schroeder, 1928, a nominal genus and species of dextral flounder known uniquely from the holotype, has been problematic regarding its identity and taxonomic status since its description. Previous treatments considered this dextral flatfish as a possible member of the dextral flounder family Poecilopsettidae or suggested it as a reversed individual of a sinistral paralichthyid species (either Etropus microstomus or Citharichthys arctifrons). However, its identity and status have never been confidently resolved. Following detailed examination of the holotype of N. macrops and comparison with other taxa, the identity and status of this species is resolved. Except for features determined to be anomalous in this specimen (dextral symmetry and short, ocular-side upper jaw), counts, measurements, and other morphological characters (e.g, arrangement of pelvic fins, position of urogenital papilla, and pattern of caudal skeleton ossification) of N. macrops agree with those of Citharichthys arctifrons Goode, 1880. Thus, N. macrops is identified as a reversed individual of the sinistral C. arctifrons. Accordingly, based on this finding, Neoetropus is relegated to the synonymy of Citharichthys Bleeker, 1862, and N. macrops becomes a junior synonym of C. arctifrons Goode, 1880. The reported capture location for this specimen (off the mouth of the Potomac River in Chesapeake Bay) is suspect because of its extremely unusual occurrence for C. arctifrons and discrepancies in documentation associated with this specimen.

The predator attraction (PA) hypothesis proposes that chemicals released from the skin (Schreckstoff) of an injured fish during a predation event attract nearby piscivorous fishes, which then compete for the prey. The confusion of this additional competition may allow the injured fish to escape. This is an alternate hypothesis to kin selection for the evolution of fish alarm systems, particularly in the superorder Ostariophysi. Schreckstoff is found in the skin of ostariophysans and some unrelated taxa, whereas muscle is not known to possess any unique pheromones. I tested the PA hypothesis using a natural assemblage of southeastern fishes. Micropterus punctulatus (Spotted Bass) were exposed to skin (Schreckstoff) and muscle (non-Schreckstoff) extracts from five co-occurring prey species, Cyprinella venusta (Blacktail Shiner), Pimephales vigilax (Bullhead Minnow), Gambusia affinis (Western Mosquitofish), Fundulus olivaceus (Blackspotted Topminnow), and Lepomis macrochirus (Bluegill). Micropterus punctulatus did not increase foraging behavior after exposure to skin extract from any of the five potential prey species; however, there was an increase in foraging behavior after exposure to muscle extract from C. venusta. The PA hypothesis was not supported by this study, and other influences on the evolution of this system are proposed.

Some amphibian larvae develop brightly colored or black tail fins when reared in ponds with predaceous insects. The conspicuous tail has been proposed to lure predator strikes toward the tail and away from the more vulnerable head/body region. We tested this hypothesis by presenting model tadpoles that differed only in coloration to Aeshna dragonfly larvae. The models had either a dark body and pale tail, a dark spot in the middle of the tail, or a dark spot near the tip of the tail. Almost all models with plain tails were struck on the head/body, whereas those with dark spots in the tail were struck significantly more often on the tail. Because living tadpoles survive better when attacked on the tail than on the head, our results show that tail coloration can protect tadpoles from predators at close range.

We describe methods for preparing dry skeletons of virtually any osteichthyan species with a well-ossified skeleton, including very large specimens (e.g., > 1 m Megalops atlanticus). Our approach differs from those conventionally used to prepare skeletons of tetrapods in that (1) fairly complete dissection of the specimen is required at the outset of processing; and (2) we use an alcohol dehydration step to rapidly dry the specimen. Similar techniques can be used to prepare well-calcified chondrichthyan skeletons. We also outline the steps for making Ridewood dissections of the skull. Dry, partially articulated skeletons prepared by these methods can be stored indefinitely in acid-free containers in an environmentally controlled space (21 C ± 3 C; Rh = 40% ± 5%) in pest-proof specimen cases. Although a truism of anatomical research is that you cannot learn everything from studying one specimen or one type of preparation, partially articulated dry skeletons are useful for research ranging from phylogenetic investigations to age and growth analyses to functional morphology, making them of great and lasting value to any collection.

In Neotropical streams, benthic sediment affects community structure and may impose energetic costs for some species yet to be a resource for others. This study tested the hypothesis that removal of benthic sediment through ingestion by Rana palmipes (Ranidae), a detritivorous tadpole, facilitated the growth of Ancistrus triradiatus (Loricariidae), an algivorous armored catfish. We hypothesized that sediment removal by Rana would reduce energetic costs to respiration or digestion encountered by Ancistrus when grazing on periphyton and increase available periphyton biomass. Growth of Ancistrus was measured in a Venezuelan piedmont stream in enclosure cages in which the presence of Rana and ambient sediment levels were manipulated. Benthic sediment accumulation differed significantly between treatments. Growth of Rana was greater when sediments were present than when sediments were removed. However, there was no effect of sediment removal on Ancistrus growth. Total biomass of periphyton did not differ between treatments, because epipelic diatoms were abundant in benthic sediments and presumably compensated for any negative effects of shading by sediments on total periphyton biomass. Organic-rich sediment in this system provides a net energetic benefit to Rana. The consequences of sediment for Ancistrus are less clear, but we found no evidence of a net cost. If interspecific facilitation by Rana occurs, it is likely limited to systems where sediment is organic-poor or to species for which costs of organic-rich sediment exceed benefits.

We assessed factors related to the occurrence of allopatric and sympatric Paiute Sculpin (Cottus beldingi) and Mottled Sculpin (Cottus bairdi) in the Salt River watershed of Wyoming and Idaho, 1996–1997. Sympatric occurrences of Paiute Sculpin and Mottled Sculpin were found in downstream segments of tributaries across a wide range of elevations, stream temperatures, channel slopes, and stream sizes. Allopatric Paiute Sculpin was found in small, high-elevation streams with low summer water temperatures, high channel slopes, large rocky substrates, and low densities of Brown Trout (Salmo trutta). Allopatric Mottled Sculpin occurred in spring streams that were wide and deep, dominated by fine substrate, and supported high densities of Brown Trout. Mottled Sculpin was absent from all tributaries on the eastern side of the drainage where streams have low summer water temperatures, high-gradient channels, and barriers that can influence upstream movements. This study suggests that stream geomorphology, thermal characteristics, local habitat conditions, and nonnative fishes differentially influence the occurrence of Paiute Sculpin and Mottled Sculpin.

Populations of Physalaemus petersi show extraordinary variation in the expression of facultative complex calls. Previous studies have shown that a structure in the larynx, the fibrous mass (FM1), is correlated with variation in production of the complex call among taxa in the Physalaemus pustulosus species group. We tested the hypothesis that the variation in the presence of call complexity that occurs within P. petersi mirrors the same laryngeal variation associated with complex calls among other species of the genus. We examined calls and larynges of P. petersi from populations on a north-south transect on the western side of its Amazonian distribution. All four populations of P. petersi (Peru and Brazil) in the south produce complex calls, whereas only one population of five in the north (Ecuador) produce complex calls. We compared larynges of four populations of P. petersi, two that produce complex calls and two that do not. We then compared them to larynges of P. pustulosus, which produces complex calls, and to Physalaemus coloradorum, which does not produce complex calls. The FM1 is significantly larger in populations of P. petersi that produce complex calls than those without complex calls. FM1 sizes of populations of P. petersi were more similar to other species with the same call type than they were to populations of their own species with a different call type. These data suggest several interpretations of the evolution of complex calls and the associated underlying morphology.

The Ashy Darter, Etheostoma cinereum (Percidae: subgenus Allohistium), is restricted to flowing pools of relatively silt free, medium-sized rivers in the Cumberland, Duck and Tennessee River drainages in the southeastern United States. Degradation of these habitats within these drainages has fragmented the range of E. cinereum into several disjunct populations and eliminated it from many historical localities. Phylogenetic analysis of cytochrome b sequence from individuals (n = 14) representing each of the extant populations of E. cinereum indicated genetic differentiation among populations inhabiting the Cumberland, Duck, and upper Tennessee River drainages. These analyses are concordant with previously noted patterns of morphological variation and minimally support three different management units (MU) currently recognized as E. cinereum. Efforts to conserve these distinct MUs should be considered in management attempts.

In most parts of central Europe the hybridogenetic water frog Rana esculenta lives (and mates) in mixed populations with its parental species Rana lessonae. Ratios of parental and hybrid animals vary from 1:9 to 9:1 among ponds, depending on various biotic and abiotic factors. These factors may directly cause the ratio differences through species-specific effects on larval performance, but previous experimental studies under laboratory and seminatural conditions produced conflicting results as to how parental and hybrid tadpoles respond to these factors. We investigated larval development and relative recruitment of juveniles in a natural population at three sites that differed ecologically. Species ratios at the different stages (eggs, tadpoles, metamorphs) and body size of tadpoles and metamorphs were compared. Differences in timing of reproduction and larval development were more pronounced within species between ponds than between species within ponds. During the egg and tadpole stages, hybrids outnumbered parental larvae by 60:40, but this ratio reversed during metamorphosis. Higher mortality rates of hybrid froglets during metamorphosis as well as lower dispersal rates after metamorphosis may explain our findings.

There was significant shrinkage in the body lengths of larvae of the myctophid fish Diaphus slender-type spp. for the first two weeks after they were preserved in 5% and 10% formalin, 70% and 90% ethyl alcohol, and 70% isopropyl alcohol solutions. The shrinkage was greatest in 70% isopropyl alcohol, followed by 90% ethyl alcohol, 70% ethyl alcohol, and the formalin solutions. No significant difference in shrinkage was observed between the 5% and 10% formalin solutions. Linear regressions described the relationships between body length before and after 140 days of preservation.

Six related studies were conducted with four captive juvenile Kit Foxes (Vulpes macrotis) to test the hypothesis that blood-squirting from eye-socket tissues by Texas Horned Lizards (Phrynosoma cornutum) is a canid antipredator defense. In 16 trials, naive “hungry” foxes killed and ate adult Yarrow's Spiny Lizards (Sceloporus jarrovii; eight of eight trials) slightly more frequently than adult P. cornutum (six of eight trials). Adverse responses by foxes (head shaking) were seen in five of six trials in which Phrynosoma squirted blood. Later these experienced foxes, fed ad libitum, killed and ate mice (eight of eight trials) while largely ignoring P. cornutum (one killed and eaten in eight trials), suggesting a learned aversion to horned lizards as prey. During attacks on mice smeared with horned-lizard blood, foxes displayed behaviors typical of predatory encounters with horned lizard prey (head shaking and prey tearing). These prey-handling behaviors were in striking contrast to those elicited by untreated mice and by mice treated with mouse blood, demonstrating that horned-lizard blood (and its chemical constituents) altered normal behaviors toward mouse prey. Prey-handling times for mice treated with horned lizard blood were significantly longer than mouse-only treatments. Responses of foxes to mice coated with horned lizard Harderian- and lacrimal-gland tissues coupled with responses to mice coated with systemic horned-lizard blood, mouse blood, and untreated mice suggest that (1) no defensive chemicals are added to the blood by orbital glands before blood ejection, and (2) active antipredator chemicals are carried in the circulating blood as well as in squirted blood. In four trials, foxes attacked “de-horned” horned lizards; a role for cranial horns in facilitating predator hesitancy prior to blood squirting is proposed. Evidence is presented that horned lizards visually identify and categorize foxes as appropriate predators for a blood-squirting defense. We conclude that, in many predator-prey encounters with wild canids, blood-squirting by Texas Horned Lizards is an effective chemical defense. We propose a scenario for the evolution of this unique defense and suggest that the defensive compounds found in the blood may be sequestered from the seed-harvester ant prey of horned lizards.

Females of iteroparous species may compromise between contrasting reproductive strategies. They should balance the amount of energy devoted to reproduction against the energy saved for growth and survival, and they should compromise between the quantity versus the quality of offspring. In the present paper, we analyze these trade-offs in European Green Toads (Bufo viridis). We define reproductive investment in terms of clutch dry mass, number of eggs, and mean ovum dry mass, whereas we describe the amount of resources saved for growth and survival (somatic investment) with a fat index derived from the total body electrical conductivity (TOBEC) of postspawning females. Our results indicate that larger individuals produce larger clutches, both in the number and size of eggs. Females with higher reproductive effort, however, also show a larger somatic investment regardless of size. We show that females of similar size invest similar proportions of resources in reproduction, so that those in good condition not only show larger reproductive effort than lower-quality females but also store larger amounts of resources for growth, survival, and future reproduction.

Heptapterus collettii Steindachner, 1881, a catfish described from La Plata basin in South America, has a puzzling set of characters for Neotropical siluriforms. Examination of one syntype shows that H. collettii does not belong to Heptapteridae or any other Neotropical family but rather to Olyra, a genus of Bagridae endemic to South Asia. Thus, it should be referred to as Olyra collettii. The species has nasal barbels on the posterior nares (shared with various Old-World catfish taxa), a wide separation between the anal and urogenital openings (shared with a large subgroup of Bagridae) and a unique structure of the first lateral-line ossicle (shared with species of Olyra). The species is similar to Olyra longicaudata, although there are significant morphometric and meristic differences. Current problems in the taxonomy of Olyra prevent conclusive resolution of the identity of O. collettii. The presence of a species of Olyra in South America is unlikely, and we consider this to be a result of mistaken locality records.

The advertisement call of Rana pipiens males may be the most complex of any temperate-zone anuran. To characterize call complexity, I analyzed acoustic properties and temporal patterning of male advertisement call notes. Calls included up to three note types (snores, grunts, and chuckles) and varied in complexity from one to 65 notes/call. Four common temporal patterns of notes in calls were observed, and transition probabilities of note pairs were nonrandom. Temperature influenced spectral and temporal properties of all note types; body size only influenced snore dominant frequency. Finally, I compared R. pipiens calls to other anurans possessing complex advertisement calls. Although the function of specific call notes has been documented in these other species, the function of call notes in R. pipiens remains unclear.

We examined the interactive effects of overwintered Bullfrog (Rana catesbeiana) tadpoles and pond hydroperiod on a community of larval amphibians in outdoor mesocosms including American Toads (Bufo americanus), Southern Leopard Frogs (Rana sphenocephala), and Spotted Salamanders (Ambystoma maculatum)—species within the native range of Bullfrogs. Spotted Salamanders and Southern Leopard Frogs were negatively influenced by the presence of overwintered Bullfrogs. Spotted Salamanders had shorter larval periods and slightly smaller masses at metamorphosis, and Southern Leopard Frogs had smaller masses at metamorphosis when reared with Bullfrogs than without. Presence of overwintered Bullfrogs, however, did not significantly affect American Toads. Longer pond hydroperiods resulted in greater survival, greater size at metamorphosis, longer larval periods, and later time until emergence of the first metamorphs for Southern Leopard Frog tadpoles and Spotted Salamander larvae. Our study demonstrated that overwintered Bullfrog tadpoles can respond to changing pond hydroperiods and can negatively impact metamorphosis of native amphibians.

Many animals use chemical cues to detect predators. However, according to the threat sensitivity hypothesis, natural selection should favor individuals able to respond differentially to the chemical cues of predators that pose different levels of risk rather than responding to chemical cues of all predators in a similar way. The behavioral responses of prey to chemical cues of predators might depend, for example, on the degree to which predators include prey in their diets. The Wall Lizard (Podarcis muralis) is under high predation pressure by saurophagous-specialist Smooth Snakes (Coronella austriaca). Wall Lizards are also an important part of the diet of the Montpellier Snake (Malpolon monspessulanus) and occasional prey of the Ladder Snake (Elaphe scalaris). Also, Wall Lizards are sympatric with the non-saurophagous Viperine Snake (Natrix maura). In the laboratory, we compared the tongue-flick rates and behavioral patterns of Wall Lizards in response to exposure to chemical signals of these four snake species that pose different risks of predation. Results suggested that Wall Lizards were able to discriminate the chemical cues of the predatory snakes from the non-saurophagous snake. However, lizards did not respond differentially to chemical cues of different predatory snakes. We suggest that other additional cues are probably needed to elicit an adequate, specific defensive response.