Evolution of coloration, urotomy and coral snake mimicry in the snake genus Scaphiodontophis (Serpentes: Colubridae)

The Neotropical hinged-tooth, coral snake mimics of the genus Scaphiodontophis are characterized by extremely long and disproportionately thick tails that are extremely fragile. Both the coloration and tail structure are putative antipredator devices. While all examples have components of the coloration that match those of the venomous coral snakes (family Elapidae), the range of variation is extreme, leading to controversy on the status of various populations, including nine named taxa. Individual, ontogenetic and geographic variation in scutellation and head, body and tail coloration were analysed to evaluate population status and possible evolutionary trends based on a sample of 183 examples from Mexico, Central America and Colombia. Variation in subcaudal counts show population differences (higher in Mexico and upper Central America) but are not congruent with geographic variation in coloration. Generally snakes from north of Nicaragua and from central and eastern Panama have a pattern of dyads (black-light-black bands separating red bands), those from Atlantic slope Nicaragua to western Panama a pattern of monads (light-black-light bands separating the red ones) and those from Colombia have both pattern types on the same snake. The dyads and/or monads may be present the length of the body and tail, restricted to the anterior part of the body or on the entire body or on the anterior part of the body and on the tail. Two or more of these variants may occur at a single geographic locality or only a single one may be present. Head and nuchal colour patterns (Z, A, V and Du) are relatively consistent geographically. The Adantic slope Guatemala, Belize and Honduras population have the A pattern, those of Nicaragua, Costa Rica and western Panama the V pattern, and those in Colombia a Du pattern. Other populations have the Z coloration. Intermediate conditions in coloration of the body and tail and head and neck are found at localities intermediate between the main pattern types, indicating intergradation among adjacent populations. Consequently, we regard these snakes as representative of a single species, Scaphiodontophis annulatus Dumeril and Bibron and the eight other names applied to various populations and individuals as synonyms. Analysis of colour pattern leads us to the conclusion that the tricolour pattern evolved from a uniform one through a lineate-spotted condition (usually present on the non-tricolour portions of the snake) through a bicolour red and black pattern to the dyadal condition. The monadal pattern in turn was derived from the dyadal one. The data further indicates that tricolour components first appeared anteriorly and progressively expanded posteriorly. The evolutionary sequence for the head and nuchal pattern appears to be A → Z → V → Du S. annulatus has a series of jaw and tooth specializations designed for rapid processing of hard-bodied prey found during diurnal foraging in the leaf-litter. Urotomy in this species involves intervertebral tail-breakage (pseudoautotomy) without regeneration. Evidence is presented supporting the long-tail multiple break hypothesis as applicable to Scaphiodontophis and other snakes with similar tail morphology (specialized pseudoautotomy). This is in contrast to snakes with similar tail morphology (specialized pseudoautotomy). This is in contrast to Coniophanes and other snakes with a high incidence of urotomy having long but unspecialized tails (unspecialized pseudoautotomy) without multiple breaks over time. All Scaphiodontophis colour patterns have a general resemblance to that of venomous coral snakes and offer protection from generalizing predators having innate or other triggered responses to coral snake colours. The aposematic effect is enhanced by tail thrashing and head twitching behaviours. The characteristic foraging pose of S. annulatus, which tends to expose the head and anterior body, makes even the incomplete tricolour pattern effective as an antipredator defence. No evidence supports the idea that tail thrashing or the incomplete tricolour pattern directs the predator attacks to the tail to expedite pseudoautotomy. Coral snake mimicry and specialized pseudoautotomy are shown not to be co-evolved and pseudautotomy seems to have evolved long before mimetic coloration in this genus.     

The status of Pliocercus and Urotheca (Serpentes: Golubridae), with a review of included species of coral snake mimics

The generic name Urotheca Bibron, 1843 is revived for a group of Neotropical colubrid snakes diagnosed by a long, thickened but fragile tail and the presence of a specialized naked pocket on the asulcate surface of the hemipenial capitulum. Urotheca includes those species previously placed in the lateristriga group of the genus Rhadinaea and the coral snake mimics usually referred to the genus Pliocercus. The many names based upon the coral snake mimics are shown to represent two species at most: Urotheca elapoides, a bicolour (red and black) or tricolour (red, yellow and black) banded or ringed form found in Mexico and northern Central America and U. euryzona, which is usually bicolour (red, yellow or white and black) and ranges from Nicaragua to western Ecuador. Coloration in U. elapoides resembles closely that of sympatric species of venomous coral snakes. Local variation in coloration and a geographic trend in the colour of the light rings (usually red in the north, white to the south) in U. euryzona parallels similar colour variation in the sympatric venomous coral snake Micrurus mipartitus. These patterns of variation add strong support to the idea that the two species are mimics of the highly venomous coral snakes. Urotheca, including the non-mimetic species U. decipiens, U. fulmceps, U. guentheri, U. lateristriga, U. multilineata and U. pachyura, shares the characteristic of a very long and disproportionately thickened and fragile tail with the coral snake mimics of the distantly related genus Scapkiodontophis. Members of both genera have a very high proportion (about 50%) of the tails broken indicating a probable predator escape device. Breakage is intercentral, with a calcified cap developing over the tip of the distal surface of the new terminal vertebra unlike the situation in many lizards where there is an intracentral fracture septum and the tail is regenerated.     

Predation on snakes of Argentina: Effects of coloration and ring pattern on coral and false coral snakes

The occurrence of coral snake coloration among unrelated venomous and non‐venomous snake species has often been explained in terms of warning coloration and mimicry. In Argentina, no field tests have been conducted to confirm this mimetic association between one venomous coral species (Micrurus phyrrocryptus, Elapidae) and two non‐venomous snake species with a similar color pattern (Lystrophis pulcher and Oxyrhopus rhombifer, Colubridae). The aims of this work were to test for the possible aposematic or cryptic function of the ring pattern and coloration of coral snakes and false coral snakes from central Argentina, and to analyse whether the pattern is effective throughout the year. Predation on snakes was estimated by using non‐toxic plasticine replicas of ringed venomous and non‐venomous snakes and unbanded green snakes placed along transects in their natural habitat during the dry and rainy season. Ringed color pattern was attacked by predators despite the background color. One of the replica types was attacked more than expected during the dry season, suggesting that both shape and width of rings may influence the choice by predators. The reaction of predators towards replicas that mimic snake species with ringed patterns is independent of the geographical region, and we can conclude that mimicry characteristics are quite general when the true models are present in the area.     

Coral snake mimicry: live snakes not avoided by a mammalian predator

The occurrence of coral snake coloration among unrelated venomous and non-venomous New World snake species has often been explained in terms of warning coloration and mimicry. The idea that snake predators would avoid coral snakes in nature seems widely established and is postulated in many discussions on coral snake mimicry. However, the few workers that have tested a potential aposematic function of the conspicuous colour pattern focused exclusively on behaviour of snake predators towards coloured abstract models. Here we report on behaviour of temporarily caged, wild coatis (Nasua narica) when confronted with co-occurring live snakes, among which were two species of venomous coral snakes. Five different types of responses have been observed, ranging from avoidance to predation, yet none of the coatis avoided either of the two coral snake species or other species resembling these. As in earlier studies coatis appeared to avoid coral snake models, our findings show that results from studies with abstract snake models cannot unconditionally serve as evidence for an aposematic function of coral snake coloration.     

DIFFERENTIAL AVOIDANCE OF CORAL SNAKE BANDED PATTERNS BY FREE-RANGING AVIAN PREDATORS IN COSTA RICA

Empirical studies of mimicry have rarely been conducted under natural conditions. Field investigations of some lepidopteran systems have provided a bridge between experiments examining artificial situations and the mimicry process in nature, but these systems do not include all types of mimicry. The presence of dangerous or deadly models is thought to alter the usual rules for mimicry complexes. In particular, a deadly model is expected to protect a wide variety of mimics. Avoidance of different types of mimics should vary according to how closely they resemble the model. Coral snake mimicry complexes in the neotropics may provide natural systems in which these ideas can be examined, but there is no direct evidence that the patterns of venomous coral snakes or potential mimics are avoided in the wild. Plasticine replicas of snakes were used to assess the frequency of avian predation attempts as a function of color pattern. Avian predators left identifiable marks on the replicas, the position of which indicated that replicas were perceived as potentially dangerous prey items by birds. The number of attacks on unmarked brown replicas was greater than that on tricolor coral snake banded replicas. This result was true whether replicas were placed on natural or plain white backgrounds, suggesting that coral snake banded patterns function aposematically. In a separate experiment, replicas representing all six patterns of proposed coral mimics at the study site were attacked less often than unmarked brown replicas. Within these six banded patterns, some were attacked significantly more often than others. This study provides direct field evidence that coral snake banded patterns are avoided by free-ranging avian predators and supports theoretical predictions about mimicry systems involving deadly models.     

Disruption or aposematism? Significance of dorsal zigzag pattern of European vipers

European vipers (genus Vipera) are venomous and often have a distinctive dorsal zigzag pattern. The zigzag pattern of vipers has been suggested to be an example of disruptive colouration which reduces the detectability of a snake. However, recent studies suggest that the patterns have an aposematic function, although those experiments did not exclude the possibility of disruptive colouration. We used plasticine replicas of snakes to examine whether the zigzag pattern of European vipers provides protection from avian predator attacks via disruptive or aposematic function, or if the zigzag pattern might simultaneously serve both antipredatory functions. Experiments were conducted in the Coto Doñana National Park southern Spain. In the experiment, predation pressure caused by birds was compared between zigzag pattern (patterns were painted with and without disruptive effect i.e. breaking body outline or not), classical disruptive colouration (non-randomly placed patterns that breaks body outline) and control markings (replicas with length wise stripes and models without painted pattern) on natural and controlled backgrounds. We found that zigzag patterned snake replicas suffered less predation than striped ones regardless of the background, providing further evidence that the zigzag pattern of European vipers functions as a warning signal against predators. However, we did not find evidence that the zigzag pattern involves a disruptive effect.     

Snake Species Discrimination by Wild Bonnet Macaques (Macaca radiata)

Wild bonnet macaques (Macaca radiata) were studied in southern India to assess their ability to discriminate non‐venomous, venomous and predatory snakes. Realistic snake models were presented to eight troops of bonnet macaques at feeding stations and their behavior was video‐recorded 3 min before and 3 min after snake exposure. Snakes presented were: (1) venomous Indian cobra (Naja naja) displaying an open hood with ‘eyespots’; (2) venomous common Indian krait (Bungarus caeruleus); (3) non‐venomous green keelback (Macropisthodan plumbicolor); (4) non‐venomous rat snake (Ptyas mucosus); and (5) Indian python (Python molurus) which preys on macaques. Latencies to detect and react to the snakes were evaluated to determine initial responsiveness. Longer‐term assessment was measured as the percentage of time individuals looked at the snakes and monitored the activity of nearby individuals before and after snake detection. All snake models engendered caution and maintenance of a safe distance. Alarm calling occurred only during python presentations. The cobra engendered a startle response or running in the largest percentage of individuals after its detection, whereas the rat snake and python elicited bipedal standing or ambulating to monitor the snakes. We also examined the influence of age on snake recognition. Juveniles and subadults looked at the cobra, krait, and python for a larger percentage of time than adults did; albeit, adults looked at the python substantially longer than at the other snakes. Age differences in behavior suggest that, with the exception of the python, repeated experience with snakes in the wild moderates excitability, consistent with the likely threat of envenomation.     

Black Bear Reactions to Venomous and Non‐venomous Snakes in Eastern North America

Bears are often considered ecological equivalents of large primates, but the latter often respond with fear, avoidance, and alarm calls to snakes, both venomous and non‐venomous, there is sparse information on how bears respond to snakes. We videotaped or directly observed natural encounters between black bears (Ursus americanus) and snakes. Inside the range of venomous snakes in Arkansas and West Virginia, adolescent and adult black bears reacted fearfully in seven of seven encounters upon becoming aware of venomous and non‐venomous snakes; but in northern Michigan and Minnesota where venomous snakes have been absent for millennia, black bears showed little or no fear in four encounters with non‐venomous snakes of three species. The possible roles of experience and evolution in bear reactions to snakes and vice versa are discussed. In all areas studied, black bears had difficulty to recognize non‐moving snakes by smell or sight. Bears did not react until snakes moved in 11 of 12 encounters with non‐moving timber rattlesnakes (Crotalus horridus) and four species of harmless snakes. However, in additional tests in this study, bears were repulsed by garter snakes that had excreted pungent anal exudates, which may help explain the absence of snakes, both venomous and harmless, in bear diets reported to date.     

Diversity of warning signal and social interaction influences the evolution of imperfect mimicry

Mimicry, the resemblance of one species by another, is a complex phenomenon where the mimic (Batesian mimicry) or the model and the mimic (Mullerian mimicry) gain an advantage from this phenotypic convergence. Despite the expectation that mimics should closely resemble their models, many mimetic species appear to be poor mimics. This is particularly apparent in some systems in which there are multiple available models. However, the influence of model pattern diversity on the evolution of mimetic systems remains poorly understood. We tested whether the number of model patterns a predator learns to associate with a negative consequence affects their willingness to try imperfect, novel patterns. We exposed week‐old chickens to coral snake (Micrurus) color patterns representative of three South American areas that differ in model pattern richness, and then tested their response to the putative imperfect mimetic pattern of a widespread species of harmless colubrid snake (Oxyrhopus rhombifer) in different social contexts. Our results indicate that chicks have a great hesitation to attack when individually exposed to high model pattern diversity and a greater hesitation to attack when exposed as a group to low model pattern diversity. Individuals with a fast growth trajectory (measured by morphological traits) were also less reluctant to attack. We suggest that the evolution of new patterns could be favored by social learning in areas of low pattern diversity, while individual learning can reduce predation pressure on recently evolved mimics in areas of high model diversity. Our results could aid the development of ecological predictions about the evolution of imperfect mimicry and mimicry in general.     

Being a bright snake: Testing aposematism and mimicry in a neotropical forest

Based on color patterns and behavioral similarities, venomous coral snake Micrurus corallinus (Elapidae) may act as a model for two polymorphic species, Erythrolamprus aesculapii (Dipsadidae) and Micrurus decoratus (Elapidae). Plasticine replicas were used to investigate the aposematism of these coloration patterns and whether these species may be part of mimetic complexes in two Atlantic Forest localities in Southeast Brazil. Coral replicas were more avoided when set upon a white background, evincing that the pattern may act aposematically in contrast with light substrates. Birds attacked all four patterns equally during the mimicry experiments. Birds of prey, known to be effective in predating snakes, are quite abundant in the study areas, which may have led to this lack of avoidance. Accordingly, they predated more adult-sized replicas, which could be more dangerous. Interestingly, opossum avoided the Micrurus corallinus and Erythrolamprus aesculapii replicas that resembled the model. This suggests that opportunistic predators, as the opossum may be important selective agents in mimicry complexes.     

Post-bite Elevation in Tongue-flick Rate by Neonatal Garter Snakes (Thamnophis radix)

A post-biting elevation in tongue-flicking rate was demonstrated experimentally in neonatal, ingestively naive garter snakes (Thamnophis radix). That the snakes also exhibited apparent searching movements suggests that strike-induced chemosensory searching occurs in nonvenomous snakes lacking previous experience with food or prey chemicals. Two litters of neonates differed in numbers of tongue-flicks emitted, but had similar relative magnitudes of response across experimental conditions. The existence of post-bite elevation in tongue-flick rate (and presumably strike-induced chemosensory searching) argues for a genetic basis for these chemosensory behaviors in a nonvenomous species of snake, extending the recent finding that strike-induced chemosensory searching is fully developed in ingestively naive neonatal rattlesnakes. Possible patterns of evolution of post-bite elevation in tongue-flick rate, and the strike-release-trail strategy of highly venomous snakes are discussed.     

Unlinked Mendelian inheritance of red and black pigmentation in snakes: Implications for Batesian mimicry

Identifying the genetic basis of mimetic signals is critical to understanding both the origin and dynamics of mimicry over time. For species not amenable to large laboratory breeding studies, widespread color polymorphism across natural populations offers a powerful way to assess the relative likelihood of different genetic systems given observed phenotypic frequencies. We classified color phenotype for 2175 ground snakes (Sonora semiannulata) across the continental United States to analyze morph ratios and test among competing hypotheses about the genetic architecture underlying red and black coloration in coral snake mimics. We found strong support for a two‐locus model under simple Mendelian inheritance, with red and black pigmentation being controlled by separate loci. We found no evidence of either linkage disequilibrium between loci or sex linkage. In contrast to Batesian mimicry systems such as butterflies in which all color signal components are linked into a single “supergene,” our results suggest that the mimetic signal in colubrid snakes can be disrupted through simple recombination and that color evolution is likely to involve discrete gains and losses of each signal component. Both outcomes are likely to contribute to the exponential increase in rates of color evolution seen in snake mimicry systems over insect systems.     

Laughing Falcon (Herpetotheres cachinnans) Predation on Coral Snakes (Micrurus nigrocinctus)1

Laughing falcon (Herpetotheres cachinnans) predation on coral snakes (Micrurus nigrocinctus) was recorded in two incidents that illustrate previously unreported variation in predatory behavior. In the first, the falcon held a live coral snake by the posterior end for an extended period of time, rather than decapitating it immediately. In the second, the falcon left a decapitated coral snake in a tree for more than 2 h before returning to recover its prey. A variety of behavioral adaptations may protect laughing falcons from coral snake venom.     

Rapid evolution of mimicry following local model extinction

Batesian mimicry evolves when individuals of a palatable species gain the selective advantage of reduced predation because they resemble a toxic species that predators avoid. Here, we evaluated whether—and in which direction—Batesian mimicry has evolved in a natural population of mimics following extirpation of their model. We specifically asked whether the precision of coral snake mimicry has evolved among kingsnakes from a region where coral snakes recently (1960) went locally extinct. We found that these kingsnakes have evolved more precise mimicry; by contrast, no such change occurred in a sympatric non-mimetic species or in conspecifics from a region where coral snakes remain abundant. Presumably, more precise mimicry has continued to evolve after model extirpation, because relatively few predator generations have passed, and the fitness costs incurred by predators that mistook a deadly coral snake for a kingsnake were historically much greater than those incurred by predators that mistook a kingsnake for a coral snake. Indeed, these results are consistent with prior theoretical and empirical studies, which revealed that only the most precise mimics are favoured as their model becomes increasingly rare. Thus, highly noxious models can generate an ‘evolutionary momentum’ that drives the further evolution of more precise mimicry—even after models go extinct.     

Diverse Evidence for the Decline of an Adaptation in a Coral Snake Mimic

Losses of adaptations in response to changed selective pressures are evolutionarily important phenomena but relatively few empirical examples have been investigated in detail. To help fill this gap, we took advantage of a natural experiment in which coral snake mimics occur on two nearby tropical islands, one that has coral snake models (Trinidad) and one that lacks them (Tobago). On Tobago, an endemic coral snake mimic (Erythrolamprus ocellatus) exists but has a relatively poor resemblance to coral snakes. Quantitative image analysis of museum specimens confirmed that E. ocellatus is a poor mimic of coral snakes. To address questions related to the functional importance of this phenotype, we conducted a field experiment on both islands with snake replicas made of clay. These results clearly indicated a strong inter-island difference in predator attack rates where snake replicas that resembled coral snakes received protection in Trinidad but not in Tobago. Further, a molecular phylogenetic analysis of the ancestry of E. ocellatus revealed that this poor coral snake mimic is deeply nested in a clade of good coral snake mimics. These data suggest that the lack of coral snakes on Tobago altered the selective environment such that the coral snake mimicry adaptation was no longer advantageous. The failure to maintain this ancestral feature in allopatry provides a compelling example of how losses of complex adaptations can occur.     

The snake hiss: potential acoustic mimicry in a viper–colubrid complex

Examples of acoustic Batesian mimicry are scarce, in contrast to visual mimicry. Here we describe a potential case of acoustic mimicry of a venomous viper model by harmless viperine snakes (colubrid). Viperine snakes resemble vipers in size, shape, colour, pattern, and anti‐predatory behaviours, including head flattening, false strikes, and hissing. We sought to investigate whether hissing evolved as part of, or separately to, the viper mimic syndrome. To do this, we recorded and analysed the hissing sounds of several individual asp vipers, viperine snakes, and grass snakes (a close relative of viperine snakes that hisses but does not mimic the asp viper). Frequencies consistently ranged from 40 to 12 000 Hz across species and individuals. All vipers (100%) and most viperine snakes (84%) produced inhalation hissing sounds, in comparison to only 25% of grass snakes. Inhalation hissing sounds lasted longer in vipers than in viperine snakes. The hissing‐sound composition of grass snakes differed significantly from that of both asp vipers and viperine snakes; however, the hissing‐sound composition between viperine snakes and asp vipers was not statistically distinguishable. Whilst grass snake hissing sounds were characterized by high frequencies (5000–10 000 Hz), both vipers and viperine snake hissing sounds were dominated by low frequencies (200–400 Hz). A principal component analysis revealed no overlap between grass snakes and vipers, but important overlaps between viperine snakes and vipers, and between viperine snakes and grass snakes. The likelihood that these overlaps respectively reflect natural selection for Batesian mimicry and phylogeny constraints is discussed. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 1107–1114.     

Phylogeography of West Indies Coral snakes (Micrurus): Island colonisation and banding patterns

In this study, we analyse New World coral snakes in a phylogenetic framework based upon an increased molecular data set, including novel sequences for the only two sympatric species known from an island (Trinidad, West Indies). Their presence in Trinidad and absence in Tobago offers a unique system to study the phylogeography of the region. We assess the tempo and mode of colonisation of Micrurus on the island, in addition to discussing the phylogenetic relationships for the genus Micrurus concerning two phenotypic traits, body and tail banding patterns. These relationships are analysed for the first time on statistical coalescent phylogeographic discrete ancestral reconstruction. We find a robust phylogenetic component in these characteristics, where strongly supported clades are recovered: prior to the onset of the Early Miocene, a triadal and tricolour tail clade composed of species from South America, and a second clade dating to the Middle‐Late‐ Miocene with monadal and bicolour tails widely distributed from North to South America. The divergence between clades dates to the Oligocene and suggests an ancient pre‐isthmus divergence supporting the arrival of the triadal clade into South America, before the connection between Central and South America was established. We find the two coral snakes present in the West Indies, M. diutius and M. circinalis, belong to the triadal and monadal clades, respectively. Guyana and Trinidad Micrurus diutius share the same haplotypes suggesting a Late Pleistocene–Holocene vicariance when sea level rises separated Trinidad from the mainland. A second lineage of diutius‐like snakes is present in Guyana and is confirmed as M. lemniscatus which is assigned as a voucher and restricts the type locality for M. lemniscatus.     

Body size as a primary determinant of ecomorphological diversification and the evolution of mimicry in the lampropeltinine snakes (Serpentes: Colubridae)

Evolutionary correlations between functionally related character suites are expected as a consequence of coadaptation due to physiological relationships between traits. However, significant correlations may also exist between putatively unrelated characters due to shared relationships between those traits and underlying variables, such as body size. Although such patterns are often dismissed as simple body size scaling, this presumption may overlook important evolutionary patterns of diversification. If body size is the primary determinant of potential diversity in multiple unrelated characters, the observed differentiation of species may be governed by variability in body size, and any biotic or abiotic constraints on the diversification thereof. Here, we demonstrate that traits related to both predatory specialization (gape and diet preference) and predatory avoidance (the development of Batesian mimicry) are phylogenetically correlated in the North American snake tribe Lampropeltini. This is apparently due to shared relationships between those traits and adult body size, suggesting that size is the primary determinant of ecomorphological differentiation in the lampropeltinines. Diversification in body size is apparently not linked to climatic or environmental factors, and may have been driven by interspecific interactions such as competition. Additionally, we find the presence of a ‘key zone’ for the development of both rattle‐ and coral snake mimicry; only small snakes feeding primarily on ectothermic prey develop mimetic colour patterns, in or near the range of venomous model species.     

Olfactory Snake‐Predator Discrimination in the Cape Ground Squirrel

Small mammals have a number of means to detect and avoid predators, including visual, auditory and olfactory cues. Olfactory cues are particularly important for nocturnal or fossorial species where visual cues would not be as reliable. The Cape ground squirrel (Xerus inauris) is a semi‐fossorial, diurnal mammal from southern Africa. Cape ground squirrels encounter multiple species of predatory snake that pursue individuals underground where visual and social cues are limited. We assessed whether Cape ground squirrels use odours to discriminate between snakes by presenting a non‐venomous snake, a venomous snake and a control odour collected on polyethylene cubes to 11 adult female squirrels from 11 different social groups. Cape ground squirrels responded by inspecting the cube, displaying snake harassment–associated behaviours and decreasing time spent in close proximity to snake odours when compared with a control. They also displayed discrimination between two snake species by increasing the frequency of cube inspection and increasing harassment behaviours with venomous snake odours when compared with non‐venomous snake odours. We conclude that Cape ground squirrels respond with snake‐specific antipredator behaviours when presented olfactory cues alone. Olfactory discrimination may be maintained by the decreased utility of other methods of predator detection: sight and group detection, in below‐ground encounters.     

Diet of the snake Philodryas nattereri (Steindachner, 1870) suggests a high plasticity of foraging in north-eastern Brazil

The knowledge about interactions between predators and prey is essential for understanding the natural history of animals, especially snakes, which are cryptic organisms that are difficult to visualize in the wild. This article reports on the predation of lizards, frogs, bats and venomous snakes by the snake Philodryas nattereri, evidencing its generalist feeding habits.