Snake Predators Research Articles

Crabs as snake predators? An observation from southern Italy leading to a comprehensive review

The recent elevation of the Western Grass Snake, Natrix helvetica, from subspecies status prompted an assessment of its natural history and ecological traits compared to closely related species. We report an unusual predation attempt by the freshwater crab Potamon fluviatile on N. helvetica sicula from Sicily, indicating an ecological interaction previously overlooked in this species. The observation suggests that this crab may utilise snakes’ muscle tissue as an additional nutrient source. This predator-prey interaction, although probably rare, adds to the understanding of the dynamics between crabs and snakes, shedding light on their interaction in freshwater habitats. To provide context for our observation and highlight its rarity, we searched through scientific literature and online sources to generate a comprehensive review of the phenomenon that examines the predatory behaviour of crabs on snakes.

Evaluation of trial reintroductions of two extinct in the wild reptile species on Christmas Island

AbstractConservation reintroductions play a vital role in the recovery of threatened species, and clear goals and objectives are essential for evaluating their effectiveness. In this study, we assessed short‐term success (<18 months) of trial reintroductions of the Extinct in the Wild blue‐tailed skink (Cryptoblepharus egeriae) and Lister's gecko (Lepidodactylus listeri) on Christmas Island. Our evaluation criteria focused on body condition, reproduction, habitat suitability, survival and population growth. In 2018 and 2019, 170 C. egeriae and 160 L. listeri were translocated from a local captive breeding facility to a 2600 m2 outdoor fenced enclosure designed to exclude a predatory snake. Despite body condition declining immediately following release for both species, it had improved by 6 months post‐release. We also detected successful reproduction in both species. Apparent survival was high for C. egeriae but low for L. listeri, and population growth was only evident in C. egeriae. We were unable to determine whether low survival of L. listeri in the release site was due to high post‐release dispersal (beyond the exclosure) or mortality. Both species selected habitats that contained high rock and log cover and avoided areas with low ground cover. Appropriate assessment criteria, as utilized in this study, enable objective and timely evaluations of reintroduction success, thereby facilitating the improvement and refinement of reintroduction protocols. Our study showed that C. egeriae can establish (in the short‐ to medium‐term) in a site from which a principal threat has been excluded and undergo rapid population growth, whereas under current conditions L. listeri cannot. However, we also demonstrate that such medium‐term success may not lead to long‐term success, as the rapid increase in C. egeriae population was reversed between 29 and 31 months after release because the barrier used to exclude an invasive predator, the wolf snake (Lycodon capucinus), was breached.

High-Voltage Toxin'Roll: Electrostatic Charge Repulsion as a Dynamic Venom Resistance Trait in Pythonid Snakes.

The evolutionary interplay between predator and prey has significantly shaped the development of snake venom, a critical adaptation for subduing prey. This arms race has spurred the diversification of the components of venom and the corresponding emergence of resistance mechanisms in the prey and predators of venomous snakes. Our study investigates the molecular basis of venom resistance in pythons, focusing on electrostatic charge repulsion as a defense against α-neurotoxins binding to the alpha-1 subunit of the postsynaptic nicotinic acetylcholine receptor. Through phylogenetic and bioactivity analyses of orthosteric site sequences from various python species, we explore the prevalence and evolution of amino acid substitutions that confer resistance by electrostatic repulsion, which initially evolved in response to predatory pressure by Naja (cobra) species (which occurs across Africa and Asia). The small African species Python regius retains the two resistance-conferring lysines (positions 189 and 191) of the ancestral Python genus, conferring resistance to sympatric Naja venoms. This differed from the giant African species Python sebae, which has secondarily lost one of these lysines, potentially due to its rapid growth out of the prey size range of sympatric Naja species. In contrast, the two Asian species Python brongersmai (small) and Python bivittatus (giant) share an identical orthosteric site, which exhibits the highest degree of resistance, attributed to three lysine residues in the orthosteric sites. One of these lysines (at orthosteric position 195) evolved in the last common ancestor of these two species, which may reflect an adaptive response to increased predation pressures from the sympatric α-neurotoxic snake-eating genus Ophiophagus (King Cobras) in Asia. All these terrestrial Python species, however, were less neurotoxin-susceptible than pythons in other genera which have evolved under different predatory pressure as: the Asian species Malayopython reticulatus which is arboreal as neonates and juveniles before rapidly reaching sizes as terrestrial adults too large for sympatric Ophiophagus species to consider as prey; and the terrestrial Australian species Aspidites melanocephalus which occupies a niche, devoid of selection pressure from α-neurotoxic predatory snakes. Our findings underline the importance of positive selection in the evolution of venom resistance and suggest a complex evolutionary history involving both conserved traits and secondary evolution. This study enhances our understanding of the molecular adaptations that enable pythons to survive in environments laden with venomous threats and offers insights into the ongoing co-evolution between venomous snakes and their prey.

Benefits of Pair-Bond Duration on Reproduction in a Lifelong Monogamous Cooperative Passerine.

AbstractLong-term social and genetic monogamy is rare in animals except birds, but even in birds it is infrequent and poorly understood. We investigated possible advantages of monogamy in a colonial, facultative cooperatively breeding bird from an arid, unpredictable environment, the sociable weaver (Philetairus socius). We documented divorce and extrapair paternity of 703 pairs over 10 years and separated effects of pair duration from breeding experience by analyzing longitudinal and cross-sectional datasets. Parts of the colonies were protected from nest predation, thereby limiting its stochastic and thus confounding effect on fitness measures. We found that 6.4% of sociable weaver pairs divorced and 2.2% of young were extrapair. Longer pair-bonds were associated with more clutches and fledglings per season and with reproducing earlier and later in the season, when snake predation is lower, but not with increased egg or fledgling mass or with nestling survival. Finally, the number of helpers at the nest increased with pair-bond duration. Results were similar for protected and unprotected nests. We suggest that long-term monogamy is associated with a better capacity for exploiting a temporally unpredictable environment and helps to form larger groups. These results can contribute to our understanding of why long-term monogamy is frequently associated with unpredictable environments and cooperation.

Egg-Clutch Biomechanics Affect Escape-Hatching Behavior and Performance.

Arboreal embryos of phyllomedusine treefrogs hatch prematurely to escape snake predation, cued by vibrations in their egg clutches during attacks. However, escape success varies between species, from ∼77% in Agalychnis callidryas to just ∼9% in A. spurrelli at 1 day premature. Both species begin responding to snake attacks at similar developmental stages, when vestibular mechanosensory function begins, suggesting that sensory ability does not limit the hatching response in A. spurrelli. Agalychnis callidryas clutches are thick and gelatinous, while A. spurrelli clutches are thinner and stiffer. We hypothesized that this structural difference alters the egg motion excited by attacks. Since vibrations excited by snakes must propagate through clutches to reach embryos, we hypothesized that the species difference in attack-induced hatching may reflect effects of clutch biomechanics on the cues available to embryos. Mechanics predicts that thinner, stiffer structures have higher free vibration frequencies, greater spatial attenuation, and faster vibration damping than thicker, more flexible structures. We assessed clutch biomechanics by embedding small accelerometers in clutches of both species and recording vibrations during standardized excitation tests at two distances from the accelerometer. Analyses of recorded vibrations showed that A. spurrelli clutches have higher free vibration frequencies and greater vibration damping than A. callidryas clutches. Higher frequencies elicit less hatching in A. callidryas, and greater damping could reduce the amount of vibration embryos can perceive. To directly test if clutch structure affects escape success in snake attacks, we transplanted A. spurrelli eggs into A. callidryas clutches and compared their escape rates with untransplanted, age-matched conspecific controls. We also performed reciprocal transplantation of eggs between pairs of A. callidryas clutches as a method control. Transplanting A. spurrelli embryos into A. callidryas clutches nearly tripled their escape success (44%) compared to conspecific controls (15%), whereas transplanting A. callidryas embryos into different A. callidryas clutches only increased escape success by 10%. At hatching competence, A. callidryas eggs are no longer jelly-encapsulated, while A. spurrelli eggs retain their jelly coat. Therefore, we compared the hatching response and latency of A. spurrelli in de-jellied eggs and their control, jelly-encapsulated siblings using manual egg-jiggling to simulate predation cues. Embryos in de-jellied eggs were more likely to hatch and hatched faster than control siblings. Together, our results suggest that the properties of parentally produced egg-clutch structures, including their vibration biomechanics, constrain the information available to A. spurrelli embryos and contribute to interspecific differences in hatching responses to predator attacks.

Loss of sea turtle eggs drives the collapse of an insular reptile community

Marine subsidies are vital for terrestrial ecosystems, especially low-productivity islands. However, the impact of losing these subsidies on the terrestrial food web can be difficult to predict. We analyzed 23 years of survey data from Orchid Island to assess the consequences of the abrupt loss of an important marine subsidy. After climate-driven beach erosion and predator exclusion efforts resulted in the abrupt loss of sea turtle eggs from the terrestrial food web, predatory snakes altered their foraging habitats. This increased predation on other reptile species in inland areas, resulting in population declines in most terrestrial reptile species. Comparisons with sea turtle-free locations where lizard populations remained stable supported these findings. Our study emphasizes the cascading effects of generalist predators and the unintended consequences of single-species conservation, highlighting the importance of understanding species interconnectedness and considering potential ripple effects in marine-dependent insular ecosystems.

The function of red and banded patterns in snakes: the ophiophagy hypothesis

Abstract The functions of bright bands in coral and other snakes have long been a puzzle. The most common opinion is that coral snakes display aposematic marks and that other red and black banded snakes in the Americas are mimics of coral snakes. I previously found that this prevailing opinion is weakly supported and unlikely, that red and bands had probably evolved independently or conjointly many times, and that a present selection for bands and red seems to exist in a significant fraction of the world. Here, I review the potential selective forces for red and bands in snakes. I find that snakes as predators are a priori plausible selective agents. I find that ophiophagy appears to be an exceptionally high risk in snakes that are themselves ophiophagous. Testing the working hypothesis that bands and red are protective against snake predators via their association with ophiophagy, as ophiophagous snakes are at higher risk, I find that the consumption of elongate vertebrates predicts band and red coloration with a very high level of confidence: red and bands are probably defensive against snake predators. Noting an apparent correlation of coloration with specific defensive behaviours and ontogenetic colour changes, I review both and find that ophiophagous snakes are remarkable for using stereotypical defences and not being aggressive, while ontogenetic colour changes seem to affect red and bands in snakes disproportionately. Defence against ophidian predators may be an unexpected natural selection shaping the appearance and behaviours of many snakes.

The function of red and banded patterns in snakes: the eyes of the beholders—also, the function of bands in fish

Abstract The functions of bright bands in coral and other snakes have long been a puzzle. A common opinion is that coral snakes display aposematic marks and that other red and black banded snakes in the Americas are mimics of coral snakes. In two previous reviews, I challenged this prevailing opinion and showed that red and bands are probably defensive against snake predators. Here, I offer a plausible mechanisms through which red and bands could be protective against ophidian predators: the function of bands is to interfere with the focusing ability of snakes, which eyes, as in fish, rely on a ball lens that moves back and forth, a peculiarity among terrestrial vertebrates. Simulations show how the spherical aberrations created by ball lenses produce local maxima in contrast when out of focus, which would feel in focus. I conjecture that red targets specific visual receptors in snakes active in low light: these receptors would have a slow and saturating response. This conjecture is justified by the lability of vision in snakes and the overabundance of red light in dim light. Those conjectures allow precise and well-respected predictions and credibly explain a wide range of observations, such as the geographical repartition of tricolour snakes, the evolution of triadal patterns, the evolution of specific triadal-like patterns in some Erythrolamprus, and the repeated evolution of black and white banded snakes with a red dorsal line. Fish eyes have similar optics, and the function of the ubiquitous fish bands could likewise be to interfere with the vision of predators.

Water depth influences survival and predator-specific patterns of nest loss in three secretive marsh bird species.

Wetlands have become increasingly rare in the United States, negatively influencing wetland-dependent birds, and many remaining wetlands are intensively managed through seasonal dewatering mimicking historic flood pulses during spring and summer. However, water around nests may provide protection from terrestrial predators, and lowering water levels during the breeding season of wetland birds may increase predation risk and exacerbate marsh bird population declines. Understanding interactions between water depth, nesting marsh birds, and nest predators is critical to aid managers in developing a multi-species management approach in emergent wetlands. During the 2020 and 2021 breeding seasons, we examined nest survival of 148 marsh bird nests (American Coot, Fulica americana, n = 1; Common Gallinule, Gallinula galeata, n = 64; and Least Bittern; Ixobrychus exilis, n = 83) and installed cameras at 78 nests to identify predators at a large, restored floodplain wetland in Illinois where the primary management technique is seasonal water removal to stimulate germination of moist soil plants. We found nest predation of, and abandonment by, Least Bittern and Common Gallinule were related to shallower water, and early season, high volume dewatering. Least Bitterns nested more commonly along wetland edges and nests farther from the shore were more likely to survive. Similarly, we found mammalian depredation of nests and nest abandonment decreased when deeper water was present around nests. Alternatively, snake predation was observed earlier in the year prior to water removal from inundated emergent vegetation. Our results demonstrate water depth may be an important deterrent of nest predators, especially mammals, during the breeding season. Further, we recommend managers delay dewatering until after the nesting season at sites where management for conservation-priority marsh birds is a focus.

Overcoming the phantoms of the past: Influence of predatory stimuli on the antipredator behavior of island pitvipers.

The reduction of predation is a potentially important factor for the evolution of the traits of an island animal species. By relaxed selection, insular animals tend to lose their antipredator behaviors. A monophyletic group of pitvipers (genus Bothrops) in southeastern Brazil, which have high genetic affinity and dwell on the mainland and adjacent islands, provide an appropriate setting to study the evolution of antipredator behavior and how different predatory stimuli can influence this behavior. The mainland Bothrops jararaca has several terrestrial and aerial predators, whereas B. insularis and B. alcatraz, restricted to two small islands, Queimada Grande and Alcatrazes, respectively, have a smaller range of aerial predators. Terrestrial predators are absent on Queimada Grande, but one potential snake predator occurs on Alcatrazes. We observed that the defensive repertoire of island snakes has not been lost, but they display different frequencies of some antipredator behaviors. The type of predatory stimuli (terrestrial and aerial) influenced the defensive response. Bothrops insularis most often used the escape strategies, especially against terrestrial predatory stimuli. Bothrops alcatraz displayed the highest rate of strike for both terrestrial and aerial stimuli. Our results indicate that even though relaxed selection may occur in island environments as compared to mainland environments, these pitvipers still retain their antipredator behaviors but with different response degrees to the two predator types.

Predation attempt on the lizard Kentropyx calcarata (Spix, 1825) by the snake Oxybelis aeneus sensu lato in a fragment of Atlantic Forest, Northeastern, Brazil

Information about predatory encounters is important for understanding predator-prey interactions and, consequently, for understanding the natural history of the species involved. In this study we report the first event of attempted predation by Oxybelis aeneus sensu lato on Kentropyx calcarata describing its behavior and comparing it with other reports of snake predation and lizard defensive behavior. We recorded the predation event in an area shaded by cashew trees in the Atlantic Forest of the Reserva Biológica Guaribas, Mamanguape, state of Paraíba, Northeastern Brazil.

The ripple effects of clines from coevolutionary hotspots to coldspots.

Coevolution has the potential to alter not only the ecological interactions of coevolving partners, but also their interactions with yet other species. The effects of coevolution may ripple throughout networks of interacting species, cascading across trophic levels, swamping competitors, or facilitating survival or reproduction of yet other species linked only indirectly to the coevolving partners. These ripple effects of coevolution may differ among communities, amplifying how the coevolutionary process produces geographic mosaics of traits and outcomes in interactions among species. In a From the Cover article in this issue of Molecular Ecology, Hague et al.(2022) provide a clear example, using the well-studied interactions between Pacific newts (Taricha spp.) and their common garter snake (Thamnophis sirtalis) predators in western North America. Pacific newts harbour tetrodotoxin (TTX), which is highly toxic to vertebrate predators. In coevolutionary hotspots, extreme escalation of toxicity in the newts and resistance to toxicity in the snakes have resulted in snake populations that retain high levels of TTX. In two geographic regions, snakes in these hotspot populations have evolved bright, aposematic colours that may act as warning signals to their own vertebrate predators. The warning signals and toxin-resistance alleles in the snake populations decrease clinally away from the coevolutionary hotpots, shaped by a geographically variable mix of selection imposed by the snakes' prey and by their own predators.

Phenotypic outcomes of predator–prey coevolution are predicted by landscape variation in climate and community composition

Abstract Landscape patterns of phenotypic coevolution are determined by variation in the outcome of predator–prey interactions. These outcomes may depend not only on the functional phenotypes that mediate species interactions, but also on aspects of the environment that enable encounters between coevolutionary partners. Exploring the relationship between coevolutionary traits and the environment requires extensive sampling across the range of the interaction to determine the relationship between local ecological variation and coevolution. In this study, we synthesized >30 years of data on predator–prey interactions between toxic newts (Taricha granulosa) and their snake predators (Thamnophis sirtalis) to explore the environmental predictors of arms race escalation. We found that geographic variation in phenotypes at the interface of coevolution was best predicted by a combination of community and climatic variation. Coevolutionary phenotypes were greatest in environments with climate favourable for newt–snake overlap. We found prey toxicity was elevated in regions with more predator species, and predator resistance was higher in regions with more prey species. Our results suggest specific environmental conditions reinforce the process of coevolution, signifying the phenotypic outcomes of coevolutionary arms races are sensitive to local ecological contexts that vary across the landscape. Read the free Plain Language Summary for this article on the Journal blog.

Genomes of two Extinct-in-the-Wild reptiles from Christmas Island reveal distinct evolutionary histories and conservation insights.

Genomics can play important roles in biodiversity conservation, especially for Extinct-in-the-Wild species where genetic factors greatly influence risk of total extinction and probability of successful reintroductions. The Christmas Island blue-tailed skink (Cryptoblepharus egeriae) and Lister's gecko (Lepidodactylus listeri) are two endemic reptile species that went extinct in the wild shortly after the introduction of a predatory snake. After a decade of management, captive populations have expanded from 66 skinks and 43 geckos to several thousand individuals; however, little is known about patterns of genetic variation in these species. Here, we use PacBio HiFi long-read and Hi-C sequencing to generate highly contiguous reference genomes for both reptiles, including the XY chromosome pair in the skink. We then analyse patterns of genetic diversity to infer ancient demography and more recent histories of inbreeding. We observe high genome-wide heterozygosity in the skink (0.007 heterozygous sites per base-pair) and gecko (0.005), consistent with large historical population sizes. However, nearly 10% of the blue-tailed skink reference genome falls within long (>1Mb) runs of homozygosity (ROH), resulting in homozygosity at all major histocompatibility complex (MHC) loci. In contrast, we detect a single ROH in Lister's gecko. We infer from the ROH lengths that related skinks may have established the captive populations. Despite a shared recent extinction in the wild, our results suggest important differences in these species' histories and implications for management. We show how reference genomes can contribute evolutionary and conservation insights, and we provide resources for future population-level and comparative genomic studies in reptiles.

A potential deimatic display revealed in a lizard

AbstractConspicuously coloured signals may evolve via sexual selection to be ornaments or armaments, thereby conferring a fitness advantage to their bearer. Conversely, conspicuous colours may also evolve under natural selection as either aposematic signals or deimatic displays that deter attacks from predators. While conspicuous colour patches may evolve for one purpose (e.g. quality indicators), they may later be co-opted for another (e.g. anti-predator defence). Phrynocephalus mystaceus is a cryptic agamid lizard with flaps in both sexes that when folded against the head are inconspicuous, but when deployed are predicted to be highly conspicuous and to increase the appearance of body size. We tested whether head flaps play a role in social signalling via courtship or as status signals during contests in both sexes. We also tested whether the head flaps have an anti-predator function by simulating predatory encounters. Head flaps were never deployed in courtship or during contests and, therefore, are unlikely to be under sexual selection. However, head flaps and their deployment during simulated predatory encounters were consistent with the predictions associated with deimatic display theory. First, head flaps were similar in form and function between sexes. Second, they were highly conspicuous to both avian and snake predators. Third, there was a rapid transition from crypsis to conspicuousness when they deployed their head flaps during a late stage of predation, the subjugation phase, consistent with an ambush. Confirmation of the deimatic display hypothesis will require future testing of receiver responses.

Uncovering Cryptic Coevolution.

AbstractStudies of coevolution in the wild have largely focused on reciprocally specialized species pairs with striking and exaggerated phenotypes. Textbook examples include interactions between toxic newts and their garter snake predators, long-tongued flies and the flowers they pollinate, and weevils with elongated rostra used to bore through the defensive pericarp of their host plants. Although these studies have laid a foundation for understanding coevolution in the wild, they have also contributed to the widespread impression that coevolution is a rare and quirky sideshow to the day-to-day grind of ecology and evolution. In this perspective, we argue that the focus of coevolution has been biased toward the obvious and ignored the cryptic. We have focused on the obvious-studies of reciprocally specialized species pairs with exaggerated phenotypes-mainly because we have lacked the statistical tools required to study coevolution in more generalized and phenotypically mundane systems. Building from well-established coevolutionary theory, we illustrate how model-based approaches can be used to remove this barrier and begin estimating the strength of coevolutionary selection indirectly using routinely collected data, thus uncovering cryptic coevolution in more typical communities. By allowing the distribution of coevolutionary selection to be estimated across genomes, phylogenies, and communities and over deep timescales, these novel approaches have the potential to revolutionize the way we study coevolution. As we develop a road map to these next-generation approaches, we highlight recent studies making notable progress in this direction.

The molecular basis of venom resistance in the non-venomous snake Sinonatrix annularis

Various snake species and snake predators have natural neutralization against snake toxins, which their antidotal abilities are commonly attributed to the intrinsic inhibitors produced by the liver, e.g., phospholipase A2 inhibitor (PLI) and metalloproteinase inhibitor (SVMPI). Sinonatrix annularis was found to possess broad-spectrum neutralization to different snake venoms in our lab. Although the anti-venom compound PLIγ has been previously characterized in our laboratory, the mechanism of resistance of S. annularis to snake venoms remains obscure. In this research, a venom affinity chromatography was constructed by immobilizing D. acutus venom to NHS-agarose beads and applied for antitoxins mining from S. annularis. The binding capacity of the venom column was validated using a self-prepared rabbit antivenom against D. acutus. Serum and liver homogenate of S. annularis were then applied to the column, the bound components were profiled using SDS-PAGE and mass spectrometry. PLIs, snake venom metalloproteins inhibitor (SVMPI), small serum protein (SSP), heat shock proteins, etc were identified. To identify their toxin targets in D. acutus venom, a reverse separation was conducted by coupling the fractionated S. annularis serum proteins to NHS-agarose beads. Fifteen toxins of five families were captured and identified as follows: PLA2s, metalloproteinases, cysteine-rich secretory proteins, snake venom serine proteinases, and C-type lectins. These discoveries increased our understanding of the capacity and mechanism of the natural neutralization of S. annularis to snake venom. These natural inhibitors are medically significant due to their powerful and broad antidotal activities, which may provide alternative and promising drug candidates for snakebite treatment.

Toxic Relationships and Arms-Race Coevolution Revisited.

Toxin evolution in animals is one of the most fascinating and complex subjects of scientific inquiry today. Gaining an understanding of toxins poses a multifaceted challenge given the diverse modes of acquisition, evolutionary adaptations, and abiotic components that affect toxin phenotypes. Here, we highlight some of the main genetic and ecological factors that influence toxin evolution and discuss the role of antagonistic interactions and coevolutionary dynamics in shaping the direction and extent of toxicity and resistance in animals. We focus on toxic Pacific newts (family Salamandridae, genus Taricha) as a system to investigate and better evaluate the widely distributed toxin they possess, tetrodotoxin (TTX), and the hypothesized model of arms-race coevolution with snake predators that is used to explain phenotypic patterns of newt toxicity. Finally, we propose an alternative coevolutionary model that incorporates TTX-producing bacteria and draws from an elicitor-receptor concept to explain TTX evolution and ecology.

Of Newts and Neurotoxins

Storytelling can stimulate learning by delivering scientific content within a narrative that increases comprehension and engagement. In this article I describe the coevolutionary arms race between toxic newts and predatory garter snakes. This engaging story centers on the use of a deadly neurotoxin called tetrodotoxin (TTX) as an antipredator defense. Some species of newts contain TTX in their tissues, but resistance to TTX has developed through convergent evolution in garter snakes and other species. TTX resistance results from mutated voltage-gated sodium channels. These channels, whether TTX resistant or not, are found in all animals and are vital to the function of nervous and muscle tissues. Through reciprocal selection, coevolution has created phenotypic matching between toxic newts and TTX-resistant garter snakes across their range in the western United States. In other words, as newts became more poisonous, garter snakes became more resistant. These results and the scientific process behind them are discussed in detail. This story can be used by educators to provide a unifying and engaging backdrop as students learn multiple aspects of biology, such as protein structure, genetics, phylogenetics, electrical signaling, evolution, and the process of science.

Toad invasion of Malagasy forests triggers severe mortality of a predatory snake

The Asian common toad Duttaphrynus melanostictus has been introduced to the eastern province of Toamasina in Madagascar, where it is feared to be having devastating effects on native communities by poisoning frog-eating predators. So far it is unclear whether the toad can invade forest habitats, and empirical evidence of its impact on native predators is lacking. We used radio tracking to investigate the spatial behaviour of adult toads in a small parcel of lowland humid forest and we quantify the disruptive effects of toad poisoning on a native frog-eating snake, the Malagasy cat-eyed snake (Madagascarophis colubrinus). We used N-mixture models to estimate the population size of cat-eyed snakes, and used the mortality events recorded in the same area to obtain an estimate of monthly mortality rate of snakes due to toad poisoning. Our results point to a drastic mortality rate of snakes that, if constant through the year, could halve the predator population, with the potential risk of local extirpation. We expect cat-eyed snake populations across rural and suburban areas of Toamasina to be severely affected by the toad invasion, and suggest that future research should investigate the effects of indirect facilitation of human-commensal rodents and the potential repercussions on human health and well-being.