The symbolic dualism of snakes: balancing social perception and ecological integrity

As the Chinese Year of the Snake recently slithered to a close, it left behind a powerful reminder of our oldest contradiction. No other animal on Earth has managed to simultaneously evoke such visceral terror and such deep, reverent veneration. It remains our ultimate paradox: throughout history, snakes have been perceived as both healers and destroyers, a contradiction that reflects directly on modern conservation biology. In our current ecological crisis, this duality manifests in how we categorize them: we see native snakes as "good," fundamental predators essential for the balance of nature, while the "bad" ones are those invasive alien species that have a catastrophic impact on biodiversity and ecosystems.

In art, the dualism of snakes is frozen in Bernini’s Bust of Medusa,
where they symbolize both monstrous terror and the tragic beauty of transformation. 
© Photo: Riccardo Scalera 

Alien snakes are animals that humans, whether intentionally or not, have moved from their natural range to new territories. Here, in the absence of natural predators and thanks to an extraordinary ability to adapt to almost any prey, they transform into a silent threat capable of unbalancing entire ecosystems. The impact of these invasions is often devastating, generating what scientists call a 'cascade effect. In the Canary Islands, for instance, the introduction of the California kingsnake is driving endemic giant lizards (Gallotia) toward extinction; likewise, in Ibiza (Balearic Islands, Spain), the horseshoe whip snake (Hemorrhois hippocrepis) is pushing the endemic wall lizard (Podarcis pityusensis) to the brink. On the oceanic island of Guam (USA), the disappearance of birds due to the brown tree snake (Boiga irregularis) has even halted forest regeneration, as there are no longer animals to disperse seeds. Beyond environmental damage, we must not underestimate health risks: these reptiles can carry parasites and pathogens, such as Salmonella or exotic viruses, which are dangerous to both local wildlife and humans.

But how do these animals reach such distant lands? The entry routes, or pathways, are manifold and often surprising. To understand these pathways, we must first dispel persistent urban legends. For example, in Italy, a popular belief suggests that vipers are reintroduced by being released from helicopters in small boxes. This is a complete myth; conservation is never conducted through such haphazard or clandestine means. The actual mechanisms of introduction are far more practical and directly linked to human activities and behaviours. The pet trade is a primary channel: animals often escape or are abandoned by owners when they become too large or demanding. It is a cruel paradox: this misguided sense of compassion leads owners to release pets into the wild, unaware that they are essentially sentencing the individual to perish in an alien habitat or, conversely, sentencing native species to extinction. In either case, the act disrupts the ecological integrity we aim to protect. There are also unintentional pathways, such as the transport of goods and waste, including military equipment in the case of the brown tree snake, or even horticulture, where eggs and small snakes travel hidden within the root balls of olive or ornamental trees, overcoming otherwise insurmountable geographical barriers. Even history teaches us how humans have reshuffled nature: from the ancient Romans or Hannibal, who launched snakes as psychological weapons, to the monks who, around the Middle Ages, introduced vipers (Vipera aspis) to Monte Cristo (Tuscan archipelago, Italy) for therapeutic purposes.

Managing this issue is one of the most complex challenges in conservation biology. The strategy must be based on three pillars: prevention, early detection and rapid eradication, and management (eradication, control, or containment). Prevention remains our most effective weapon. Through the tools of horizon scanning and risk assessment, scientists evaluate the danger of species not yet present to inform policymakers. This allows the most high-risk species to be flagged and potentially included in blacklists, which allow for action to be taken. The European Union's Regulation on invasive alien species, for example, is based on a list of "species of Union concern," which allows for the blocking of their keeping and trade before the damage is done. The kingsnake, Lampropeltis getula, is the first and only snake listed so far.

The identification cards of Lampropeltis getula
made by the European Commission for customs

To support these efforts, the scientific community is more active than ever. By working at the science-policy interface, experts are collaborating with the European Commission to produce tools not only to inform policymakers but also wildlife managers. For example, in 2020, an international workshop was organized, gathering the world's leading experts led by IUCN to share best practices. This collaboration resulted in a comprehensive report on the management of invasive alien snakes, now officially available online through the European Commission, which serves as a global roadmap for tackling these invasions. Other tools were also developed to increase awareness, such as guidance for surveillance and relevant case studies, identification guides, cards, and posters specifically for kingsnakes. These show similar species in trade for customs officers, along with similar species occurring in the field for wildlife managers. The listing of the kingsnake also allowed for action to be taken, resulting in several propagules being removed in countries like Germany, Denmark, and Ireland, as documented by the NOTSYS platform managed by the Joint Research Centre.

The report of the European Commission
on the management of invasive alien snakes

However, if prevention fails, eradication becomes a race against time that is almost impossible to win. Snakes are masters of elusion: they live underground, in trees, or move under the cover of night, and their young are virtually invisible. We must be honest: snakes are nearly impossible to manage once introduced, as current techniques are not sufficiently effective. Thus, when total removal is no longer feasible, the only options left are numerical control to reduce predatory pressure or the creation of "sanctuaries", fenced and protected areas where snakes are excluded to save species on the brink of extinction.

This presents us with a profound ethical dilemma: the removal of an alien individual is not an act of hate, but a necessary choice to protect the right to survival of an entire native species. Ultimately, the responsibility is ours. The primary challenge is not merely to remove and manage invasive alien snakes, but to change human behavior. We must ensure that the importance of keeping snakes in their own ecosystem and not moving them beyond their natural range is recognized as key to respecting the boundaries that evolution has drawn over millions of years.

The fine art of biological invasions foresight

Much like a crystal ball, horizon scanning allows us to catch a fleeting glimpse into the future. This is the magic of forward-looking studies, the same which allow businessmen to decide where to invest and meteorologists when to pack an umbrella. For ecologists, this same foresight reveals which biological storms are gathering at the border. In invasion biology, waiting for the rain to fall means you are already soaked. Invasive alien species, alongside climate change and habitat destruction, are primary drivers of global biodiversity loss. Beyond disrupting ecosystems, they impact human health, the economy, and act as subtle vectors for wildlife pathogens. Because managing an invasion after establishment is a massively expensive and often losing battle, science is striving to shift from reactive management to proactive planning. This is precisely where horizon scanning steps in as the answer.

This approach is already successfully applied in sectors like plant and animal health to intercept agricultural pests and livestock diseases before they trigger outbreaks. Notably, this cross-sectoral synergy was a central theme at the 3rd International Scientific Workshop on Horizon Scanning for Plant Health, organised by the European Food Safety Authority (EFSA), where an international panel of experts addressed these shared challenges. The workshop's official summary features a presentation of my own contribution to the field, which serves as the foundational basis for this article. In invasion ecology, this foresight specifically targets the human activities driving species movement. By analyzing trade routes and climate shifts, it flags "door-knocking" species: high-risk disruptors sitting just outside our borders, ready to invade.

In the European Union for example, to prioritize threats within Regulation (EU) No 1143/2014, the European Commission launched two major region-wide horizon-scanning exercises in 2015 and 2026. Both exercises utilized the Delphi method, a consensus framework where experts across five thematic groups (covering plants, vertebrates, terrestrial invertebrates, marine, and freshwater ecosystems) first drafted preliminary risk scores through literature reviews and then finalized them during a collaborative workshop. Throughout this process, species were systematically evaluated based on their likelihood of arrival, establishment, spread, and potential biodiversity impact.

The main hurdle in this predictive art is volume. The 2026 exercise faced an initial longlist of nearly 9,000 species, filtered down to some 4,000 by removing clear climate mismatches or species lacking an invasion history. Ultimately, 622 species were debated at the consensus workshop, classifying 57 as "very high risk" and 108 as "high risk." While automated tools like climate matching and occupancy analysis were implemented to streamline the screening, the results highlighted the strict limits of automation. Incomplete baseline data often led to unreliable outputs, and automated models frequently failed to capture complex ecological requirements. This proved a critical lesson: automated tools are useful for flagging risks, but they cannot replace the nuanced, qualitative judgment of expert networks. 

Crucially, horizon scanning is a prioritization filter, not a mitigation strategy, just the initial step before a full risk assessment and formal EU listing. The looming invasion of the red imported fire ant (Solenopsis invicta) in Europe exposes the challenge in this pipeline: flagged as a top priority "door-knocker" in 2015 and risk-assessed in 2017, it was officially listed only in 2022. But it was too late. The ant had already established itself in Sicily by 2019, remaining undetected until 2023. This case proves that even the most advanced foresight tools fail without rapid information flow and immediate policy enforcement.

Fire ant (Solenopsis invicta)
Drawing made by Massimiliano Lipperi © European Commission

The fire ant case demonstrates that without a seamless, rapid handoff from foresight to policy enforcement, the best-scanned horizon remains just a picture of an impending, unmitigated crisis. For a forward-looking study to truly protect biodiversity, the scientific alarm must be met with an immediate, synchronized, and aggressive legislative response. Eventually, the critical challenge is now to integrate, harmonize, and find deep synergies between the methods applied in the field of biological invasions with those utilized in animal and plant health. Alongside this cross-sectoral alignment, we must place a strong emphasis on increasing the efficiency of automated studies. By refining these digital frameworks to minimize baseline data gaps, we can optimize resources, reduce the reliance on purely manual filtering, and perform much quicker screenings. Ultimately, bridging the science-policy gap, embracing automation responsibly, and fostering cross-disciplinary collaboration remain the most critical steps in transforming these prioritized lists from mere warnings on a page into tangible, swift conservation outcomes.

Beyond decoration: restoring the role of plants in global health

Though plants are omnipresent in our daily lives, we frequently fail to perceive them as anything more than inert green scenery. We are accustomed to valuing them merely as decorative elements or as simple providers of food and oxygen, yet we often overlook the profound impact they have on ecosystem resilience and our overall well-being. We have become so used to treating the botanical world as a silent setting that we forget plants are actually lead actors in our health and survival; while experts remain preoccupied with animals and pathogens, they risk ignoring the very entities that possess the power to either ignite or prevent the next global health emergency.

The One Health approach is an integrated framework designed to recognize the fundamental interdependence of human, animal, and environmental health. Its primary objective is to move beyond siloed management toward a collaborative system that fosters long-term prevention and ecosystem resilience rather than just reactive crisis management. However, current implementations often suffer from "plant-blindness," where plants are treated as a passive backdrop rather than as dynamic and active determinants of health. As described in the policy brief published within the B-Cubed and OneSTOP projects, this gap creates a structural bias toward animal and pathogen focused policies, leading to suboptimal responses and missed ecological drivers. Within the One Health framework, this "plant-blindness" causes us to overlook organisms that serve both as the essential foundation of our well-being and as the hidden drivers of emerging health crises.

A significant part of this problem stems from a governance and implementation gap where practitioners frequently misuse the terms "environment" and "ecosystem" as synonyms. In practice, the "environment" is often reduced to abiotic factors like climate and pollution, which obscures the specific role of plants as health actors. By strictly defining the environment as the physical context and the ecosystem as an interactive biological network in which plants are central, we can better integrate plant health into the One Health framework.

Plants serve as the essential foundation of health, underpinning everything from global food security and primary healthcare to the stability of microbiomes that influence human and animal immune systems. A critical but frequently ignored aspect of this relationship is the role of invasive alien plants, which act as direct drivers of disease and systemic health stressors. Ecologically impoverished systems are not only less tolerant to climate change but are also more susceptible to biological invasions, as the lack of plant competition allows invasive alien species to dominate and further degrade valuable land and disrupt delicate ecosystems. While diversity provides resilience, the spread of invasive alien plants like Prosopis juliflora undermines food security and heightens human vulnerability to allergies and vector-borne diseases, including malaria transmission. Other species may trigger direct pathologies, such as ragweed-induced (Ambrosia artemisiifolia) allergies or skin damage from giant hogweed (Heracleum mantegazzianum), and facilitate the proliferation of disease vectors like the water hyacinth (Pontederia crassipes) does for mosquitoes.

Water hyacinth surrounded by mosquitoes
(AI-generated image)

To address these systemic gaps, it is essential to explicitly include alien plant-driven health risks within One Health monitoring and governance. Prioritizing native plant diversity and monitoring biological invasions is essential to building the "biotic resistance" required for systemic disease prevention. By investing in taxonomic expertise and integrating plant community data into vector monitoring, the One Health approach can become truly operational and capable of sustaining healthy environments for all. 

Of people and snakes: slithering between ancient myths and community science

There is a truly unique event that takes place every year in the heart of Italy, where the boundaries between the human and the wild simply dissolve. It is a story of snakes. Of people and snakes. The ancestral fascination - that unique mix of wonder and fear - finds a profound synthesis in Cocullo, a small village nestled in the heart of the Abruzzo Apennines. Here, the Feast of San Domenico Abate takes place. It is a unique sacred-profane ritual where the statue of the Saint is draped in live serpents and carried through the streets by serpari (snake-catchers). The rite symbolizes the reconciliation between man and nature, transforming ancestral fears into a powerful celebration of spiritual protection and environmental stewardship.

San Domenico draped in live four-lined snakes 
during the procession of the serpari 
© Photo: Riccardo Scalera 

This unique cultural landscape has evolved into a visionary, long-term "community science" event on snake protection, the greatest and genuine ever seen in Italy and beyond. In the weeks leading up to the May 1st celebration, the serpari traverse the surrounding territory to collect the snakes, providing a rare and precious opportunity to investigate the biology of these species in their natural habitat. By bridging the ancient skill of the search with the modern rigor of data collection, their precious knowledge and respect for nature and wildlife have developed into a fascinating crossroads where modern herpetological science meets tradition, effectively blending cultural heritage with the systematic gathering of biological data. In addition to that, the event also become a very popular tourist attraction for enthusiasts and curious people of all ages coming from all over the country and beyond.

This sacred-profane ritual hence allowed for the collection of a vast amount of data on snakes, effectively transforming the local serpari into true "custodians of biodiversity." Working under official permits, these practitioners treat the animals with immense care and respect, fostering a deep sense of environmental responsibility that permeates the entire community. This shared commitment is what has enabled over 15 years of rigorous scientific monitoring, ensuring that the ancient tradition serves a modern ecological purpose. Data are collected by renowned herpetologists with the vital contributions of leading veterinarians from the University of Bari and other experts who work in close step with the local serpari. A fundamental aspect of this work is that all captured specimens are marked with a PIT tag (microchip). This allows for individual identification and serves as a crucial measure to abide by the law. Since these species are protected under the EU Habitats Directive, the marking system ensures compliance with the specific legal derogation granted for this rite, providing a transparent and regulated framework for the study of the four-lined snake (Elaphe quatuorlineata), the Aesculapian snake (Zamenis longissimus), the barred grass snake (Natrix helvetica), the smooth snake (Coronella austriaca), the southern smooth snake (Coronella girondica), and the green whip snake (Hierophis viridiflavus).

A rare smooth snakes captured by the serpari
© Photo: Riccardo Scalera 

Data collected across the years confirms the sustainability of this practice. Many individuals are recaptured time and again, showing regular growth and no evidence of harm from the ritual, proving that these reptiles are thriving within their ecosystem despite their annual role in the procession. Crucially, the project integrates a One Health perspective through in-depth veterinary investigations that monitor the reptiles' health as a vital bio-indicator of the broader environment. By recognizing that the well-being of the community, the wildlife, and the local habitat are inextricably linked, the event has become a fundamental platform for ecological research and public health awareness.

A green whip snake being examined for mites
© Photo: Riccardo Scalera 

This evocative atmosphere and the delicate balance between science and society is masterfully captured in the book Slither by Stephen Hall, where the story of this celebration is described with rare sensitivity and depth. Having had the privilege of meeting the author and sharing the experience of the festival with him, I was impressed by his extraordinary personality and his rich background as a journalist specifically focusing on science and society - and his long-time tenure as a correspondent in Italy. For those interested in the many unknown facts and stories of snakes and humans, this book is an essential guide. Stephen Hall explores a wide array of compelling themes, ranging from the surprising parental care found in rattlesnakes to the biological marvels of pythons that physically remodel their internal organs to digest each meal. He further delves into the rapid evolution of venom as an environmental adaptation and even traces the roots of holistic medicine back to the proto-hospitals of Pindar’s Greece.

These stories serve to reconcile myth with biology, much like the rite of Cocullo itself. Ultimately, the annual Feast of San Domenico Abate stands as a powerful symbol of community resilience, successfully bridging ancient faith with modern ecological stewardship while solidifying its status as a vital piece of Italian cultural heritage.