The Italian wall lizard: a conservation tale of a successful invader

If I could return as an animal, I'd like to be a lizard—an Italian wall lizard, you bet! Known to scientists as Podarcis siculus, this miniature, speedy dart of green is one of the world's most thriving and adaptable lizard species, and also a remarkably successful invader. Many introduced populations are now found far beyond their native range, which largely coincides with the Italian peninsula. Their global spread is often facilitated by humans, whether intentionally as pets or accidentally as hitchhikers on cars and trains. They can also be transported as contaminants alongside goods like building stones or nursery plants, particularly olive trees. Even the movement of Italian troops during the Spanish Civil War played a role in their introduction to Spain. But, as is often the case with alien species, once established outside their native range, they can quickly become a disruptive visitor that threatens local wildlife. Not surprisingly, some introduced populations of Italian wall lizards have been receiving increasing attention in recent years. A small population in Athens, Greece, was indeed eradicated a few years ago (mostly with the help of stray cats, for once a welcome ally of conservation biologists). Similarly, a few individuals were promptly removed at an early stage of introduction in Buckinghamshire, UK, and La Rioja, Spain.

Italian wall lizard introduced in Corsica
© Photo: Riccardo Scalera

However, the most interesting project targeting Italian wall lizards is taking place in the Aeolian archipelago in Sicily, Italy. The Aeolian Islands are a fascinating, arid group of small islands and rocks that emerged from volcanic activity in a beautiful corner of the Mediterranean Sea some 500 000 years ago. Here, the endemic Aeolian lizard (Podarcis raffonei) thrived until the introduction of the Italian wall lizard. The endemic species is now confined to three small rocky islets—Strombolicchio, La Canna, and Scoglio Faraglione—and a very small stretch of land on Vulcano Island, where the progressive expansion of the Italian wall lizard has cornered the remnant population. To combat this decline, expert researchers from a number of institutions, led by Roma Tre University, have launched the project LIFE EOLIZARD, co-funded by the European Commission, with many other partners including L'Aquila University, the Rome zoo (Bioparco), CNR and Triton.

A view to the Aeolian archipelago from Lisca Bianca
© Photo: Riccardo Scalera 

This ambitious project, aimed at halting and reversing the decline of this unique lizard, is structured around three main pillars: a) removing a threat to an endangered species, b) captive breeding of the endangered species, and c) reintroducing the endangered species. The introduced populations of Italian wall lizard on the two small islets of Lisca Bianca or Bottaro will be completely removed to turn them into a sanctuary for the reintroduction of the endemic Aeolian lizard. In parallel, Aeolian lizards are being successfully reproduced at both the Rome zoo (Bioparco) and a dedicated breeding center on Salina Island, making the release of hundreds of new lizards possible for recovery purposes. In this sense, EOLIZARD is a truly unique project that integrates the removal of an alien species with the reintroduction of a captive-bred population facing imminent extinction. This combination of measures is expected to increase the global population size by up to 140%, thus offering an unparalleled opportunity for the endangered Aeolian lizard to significantly boost its chances of survival. It is also worth mentioning that, in consideration of the human dimension, the invasive alien lizards are not killed but relocated to a nearby island where genetic analysis shows a sibling population already exists: thousands of little lizards will be gently captured by trained experts luring them into safe traps with some sweet juice, then quickly transported to the verdant island of Panarea and released into suitable habitats. This humane approach is one of the project's most innovative features.

Aeolian lizard captive bred at the Rome zoo (Bioparco)
© Photo: Riccardo Scalera

In a nutshell, EOLIZARD is exceptional because it operates as a living laboratory. This allows researchers to explore the ecological and evolutionary dynamics of both species and their ecosystems, including their relationship with human activity. Furthermore, comprehensive genetic analysis and health screenings performed on all animals provide a unique opportunity to understand population origins and the emergence of diseases, including potential zoonoses. The global significance of these efforts was widely recognized at an international workshop held in early June 2025 in Malfa, Salina Island, where world experts convened to share experiences on managing alien lizards and to discuss ideas for future research and collaboration. Insights shared at the workshop, drawing from a global dataset on lizard management, highlighted a critical hurdle: the lack of comprehensive reporting on management projects. 

EOLIZARD workshop participant
© Photo courtesy of Massimo Recupito (Triton)

Globally, approximately 20 species of invasive alien lizards are currently under some form of management, as highlighted at the EOLIZARD workshop. In Europe alone, where 50-70 species have been introduced or translocated outside their natural range within the region, the primary challenge with invasive lizards often comes from its own native Podarcis species. The Italian wall lizard for example is a remarkably successful and widespread invader, with established populations across much of Europe and beyond, including in Spain, Portugal, France, Switzerland, Greece, Croatia, Albania, Montenegro, Romania, Poland, Germany, Turkey, Tunisia, Libya, Azerbaijan, and the USA. The workshop's outcome was a clear call to action: we must develop effective methods for rapidly detecting and removing invasive lizard threats and, most importantly, implement measures to protect native species. In this context, the importance of the management and research activities carried out within the EOLIZARD project cannot be overstated. Never before has such an ambitious project been designed for a small lizard, neither in terms of the target alien population's size nor the area to be cleared. However, the project isn't without its risks. The complete removal of alien lizards could be quite challenging, especially when targeting the smartest or luckiest survivors, including newborns that may have escaped initial control efforts. Nevertheless, EOLIZARD has the potential to be a model for replication in many other areas.

This is a concrete example of the European Commission's conservation efforts. The Commission's approach is twofold: it aims to facilitate overall policy for alien species while also guiding local action. It achieves this by specifically funding innovative pilot, demonstration, and best practice projects through the LIFE programme, with the goal of encouraging beneficiaries to actively replicate and scale up the results. Furthermore, these efforts align with previous initiatives, such as the detailed management note for the Italian wall lizard. This note, also made for a number of other species, serves as an example of the measures needed to address threats from species that are native to some parts of the EU but invasive in others. These resources provide practitioners with crucial information on prevention, surveillance, rapid eradication, and long-term management. While the LIFE EOLIZARD project and the European Commission's mobilized resources are vital, the workshop's outcomes were clear: we must urgently improve data sharing, foster innovation in management techniques, and collectively raise the priority of addressing the subtle yet significant threat posed by invasive alien lizards. 

In the meantime, without stricter biosecurity measures, the Italian wall lizard will inevitably continue its global expansion. The lizard not only possesses all the ecological traits of a successful invader but is also actively supported by humans from around the world who enjoy having them sunbathing in their yards. So, as a take-home message, if you love Italian wall lizards as I do, don't take them with you abroad. Instead, just enjoy a visit to the Italian peninsula. You'll see plenty of them there and bring home great memories too!

LIFE and alien species: over 30 years of success stories

On 21 May 1992 two “monumental” pieces of nature protection legislation were adopted in the European Union (EU): the Habitats Directive and the LIFE Regulation. The former set the basis for the protection of a number of species and habitats across the region. It also led to the creation of Natura 2000, the largest coordinated network of protected areas in the world, with nearly 27000 sites across the EU. The LIFE Regulation is a financial programme that laid the foundation for the implementation of the Habitats Directive. Since then, the LIFE programme has supported over 5600 projects. They mostly focus on the actual protection of the Natura 2000 network, with its full assemblage of threatened species and habitats, but LIFE also finances projects focusing on a variety of other environmental topics, from climate change to pollution, energy, waste, water, etc. Among them, there are a good number of LIFE projects addressing invasive alien species (IAS). 

On 25 and 26 May 2023 a good representation of such projects convened together in Malaga, Spain, to a workshop on “Exchanging experiences on invasive alien species projects in Europe” organized by the LIFE INVASAQUA project. The workshop was held just a few days after this 31st anniversary of the LIFE programme and the Habitats directive.  Therefore it was not only a fantastic opportunity for invasion biologists and practitioners to meet up, but also a perfect occasion to commemorate 31 years of that successful combination between LIFE and alien species. A quick journey to rediscover how biological invasions were dealt with within the EU since 1992 may be the best way to celebrate this achievement, as this may offer the opportunity to reflect on the actual role of LIFE in shaping the IAS policy within the full region, with LIFE beneficiaries playing – even though mostly unwittingly - a major collective role thanks to the results of their activities, whose impact went well beyond the actual scope designed for the single projects. 

Today, IAS and their impact to the environment are one of the key topics addressed by the LIFE programme. But this was not always the case. For example, in 2004, when the first LIFE brochure on IAS was published, the European Commission (EC) realized for the very first time that more than 100 LIFE projects had either partially or exclusively addressed this threat between 1992 and 2002, mobilizing over 27 million euro. This was possible even without the LIFE programme having a specific strategy to support this threat, and in any case well before the EU Regulation No. 1143/2014 on IAS was on the EU policy agenda, showing the pioneering character of the LIFE programme. The key conclusions of that report were not that different from what we would find still relevant today: 

• LIFE is the main EU source of funding for field activities aimed at IAS;
• The high number of LIFE projects dedicated to IAS shows that wildlife managers perceive IAS as a major threat to biodiversity conservation;
• LIFE demonstrated that the threats posed by IAS can be addressed successfully within the Natura 2000 network. 

A new assessment of the contribution of the LIFE programme in facing the problems caused IAS was made in 2010. It was funded by the European Environment Agency (EEA), as Support for a pilot project on “Streamlining European 2010 Biodiversity Indicators”. The report including the result of this work, which also led to a Biological invasions paper, highlighted that during the years 1992-2006, the EC supported almost 200 projects dedicated to reducing or eliminating their threats, for over 44 million euro. The report confirmed that an impressive quantity of data and knowledge supported by hands-on experience had been acquired since 1992. Last, but not least, LIFE projects had been a key tool to inform and raise awareness on IAS and their impact on biodiversity and human activities. The EEA work had also the merit to show that the budget spent for such projects would provide the basis for developing an effective response indicator on IAS management (see here another relevant report and a scientific paper on the issue). Such response indicator may help measure the extent to which efforts are being made to reduce the rate of biodiversity loss due to the spread of IAS, and help laypeople and policymakers understand the relevance and the meaning of the problems linked to this issue. 

In 2014, exactly 10 years after the first brochure on LIFE and IAS, a second report was published. This allowed to update the figures for the full period between 1992 and 2013, with a total of 265 LIFE projects including measures dealing with IAS, and investing a total of some 70 million euro in the problem. 

In other words, the LIFE programme contributed to generate an impressive body of knowledge in terms of innovative actions, lessons learned, experience, best practices, and technical information, and had a key role in paving the way to the development and adoption of the EU Regulation No. 1143/2014 on IAS, which entered into force in 2015. This was a long expected piece of legislation, that the LIFE programme had definitely contributed to shape in many ways, thanks to the number of lessons learned on IAS policy and practices gathered through the implementation of hundreds of projects and measures. The EU Regulation on IAS seeks to address the problem in a comprehensive manner so as to protect native biodiversity and ecosystem services, as well as to minimize and mitigate the human health or economic impacts that alien species can have. For this purpose, the Regulation foresees three types of interventions: i) prevention, ii) early detection and rapid eradication, and iii) management. Basically, the typical measures financed by LIFE programme and implemented through this instrument even before the EU Regulation on IAS entered into force, thanks to the provisions set in the EU Nature Directives, but also to the policy documents developed by the IUCN, the Bern Convention/Council of Europe, the Convention of Biological Diversity etc. 

As a result, starting from the LIFE programme 2014-2020, IAS were formally included as a thematic priority. Therefore, as LIFE continues to finance projects targeting these measures, the programme is considered essential for ensuring a sound implementation of the EU Regulation on IAS, including the risk assessments required to inform the evolution of the list of species of Union concern, which represents the core part of the Regulation. The adoption of the EU Regulation on IAS also led a first pan European Platform meeting on Invasive Alien Species (IAS) organized in December 2017 by the Italian LIFE Integrated Project GESTIRE 2020. Over 120 persons attended the meeting, with representatives from 51 LIFE projects. Moreover, as a key output, a 142 pages booklet describing 62 LIFE projects was published: A catalogue of LIFE projects contributing to the management of alien species in the European Union. The aim was to share the many experiences and case studies, promote the assessment of strength and weaknesses of the LIFE programme in relation to the implementation of the EU Regulation on IAS, evaluate future challenges and opportunities (including links with other nature protection legislation, along with possible synergies with other EU financial resources). At the end of the workshop a document was finalized, to provide the EC and EU Member States with recommendations for improving the performances of LIFE projects on similar issues, to facilitate networking, and to contribute ensuring a sound implementation of the IAS Regulation. The main conclusions were that LIFE has been the main financial tool to deal with the threat posed by IAS in Europe, and provided impressive results in terms of successful case studies with a high replicability potential, hence a dedicated network of LIFE projects focusing on IAS should be promoted at the EU level. This should ensure appropriate information flow and replicability of project results and experiences on IAS management, including ways to involve stakeholders at all scales. 

All these publications and events, supported by a few other technical papers and reports, stressed the importance of the LIFE instrument in relation to the development and further implementation of EU policy and legislation on IAS. Additionally, several conferences and workshops were organized within the LIFE programme, with a focus on specific IAS related themes and/or regions, along with a number of other media products. Such communication and information activities are an essential component of each single LIFE project thanks to the strong element of outreach that characterizes the programme itself. Their effect has been twofold: from one side it was pivotal to raise awareness on IAS so to change people attitude towards the problem, whereas from the other side it gave the necessary visibility to the LIFE instrument itself, confirming its role as the key financial tool to fight IAS in Europe. At any event, it appeared evident that a dedicated EU network of authorities, scientists, researchers, stakeholders, wildlife managers etc should be promoted. This is key to ensure appropriate circulation of information about results and experiences from projects dealing with IAS management and prevention. 

LIFE has been so far the main and only tool supporting measures to prevent and manage biological invasions, and supported the organization of regular meetings between all actors involved in the topic, in the EU and beyond. A new call for LIFE projects has been launched. Nearly 150 million euro are available for the nature and biodiversity strand alone, plus 6.5 million euro for technical assistance replication projects. This may provide key actors and stakeholders the opportunity to get the financial resources necessary to promptly respond to new challenges, contribute to the sound implementation of the EU Regulation on IAS, and eventually play a synergic role in shaping the current and future policy and legislation on IAS, including in relation to the LIFE programme.

LIFE confirms financial support to alien species policy in Europe

On 18 June 2014 a new LIFE call has been launched, and invasive alien species (IAS) continue to be a priority issue for funding within the European Union (see previous post on the 2013 call here). The new LIFE Regulation, which establishes the EU financial Programme for the Environment and Climate Action, with a total budget set at 3.4 billion euro for the funding period 2014–2020, has been throughly revised. For example, the programme is now subdivided in the two sub-programmes Environment and Climate Action. Besides, to ensures both the necessary flexibility to achieve the LIFE Programme targets and objectives and the necessary stability for potential applicants to plan, prepare and submit proposals, a Multiannual Work Programme for 2014-17 has been adopted. 

LIFE aims at contributing to the achievement of the objectives and targets of the Europe 2020 Strategy, the 7th Union Environmental Action Programme and other relevant EU environment and climate strategies and plans. In this context, and as reported more in detail below, IAS are explicitly mentioned in the list of project topics implementing the environmental policy priorities under the three priority areas covered within the new "Environment" strand: environment and resource efficiency; nature and biodiversity; and environmental governance and information.  It is also worth remarking that now the newly revised programme – which is open to the participation of third countries and activities outside the EU - consists of a number of new categories of projects, including preparatory projects, integrated projects, technical assistance projects, capacity building projects. The project topics set in the multi-annual work programme refer to "traditional" projects in the Environment sub-programme. "Traditional" projects are indeed very similar to the old LIFE+ Nature, Biodiversity, Environment and Information projects, e.g. focusing on best practice, demonstration, pilot, and information projects. 

More in detail, within the  priority area “Nature and Biodiversity” the project topics which are given priority to contribute to Target 1 of the Biodiversity Strategy to 2020 to fully implement the Birds and Habitats Directives, thus under the Thematic priorities for Nature, include:

Projects targeting invasive alien species, where these are likely to deteriorate the conservation status of species (including birds) or habitat types of Community Interest in support of the Natura 2000 network 

Priority is also given to project topics focus on the implementation of Targets 2, 3, 4 and 5 of the Biodiversity Strategy to 2020, thus under the Thematic priorities for Biodiversity, such as:

Projects implementing actions targeting Invasive Alien Species (under Target 5 of the Biodiversity Strategy or in view of contributing to reaching the level of protection set out in descriptor 2 — Non-indigenous species of the Marine Strategy Framework Directive (1)) through actions testing and applying approaches aimed at:(a) preventing the introduction of invasive alien species, in particular by tackling pathways of unintentional introduction,(b) establishing an early warning and rapid response system, and(c) eradicating or controlling established invasive alien species on an appropriate spatial scale.

These projects shall address with their actions the three steps (prevention; early warning and rapid response; eradication/control) in a comprehensive framework, or, where one of the steps has already been addressed, their actions shall at least be clearly situated in a broader framework that links all three steps. They should be set up to improve existing — or introduce new — technical, administrative or legal frameworks on the relevant level; they should aim at preventing the broader establishment of IAS within the EU.

Finally, the project topics listed under the priority area "Environmental Governance and Information", include:

National and transnational awareness raising campaigns on invasive alien species (IAS) targeting the general public and key stakeholders including policy makers, businesses, and local, regional or national authorities.

LIFE projects focusing on IAS across the years (source: EEA report no.15/2012)

The experience of the last 20 years has shown that LIFE has been crucial to ensure the successful implementation of several activities focusing on IAS management and prevention, including new ways to address the wider IAS challenge (see "LIFE and alien species" report here). In fact, as shown in a recent report on biodiversity indicators (EEA report no.15/2012), both the number of LIFE projects funded and the relevant cost estimates have been markedly positive across the years. The relevant data have been used for the development of a set of response indicators, whose role should be primarily to track the measures being implemented to mitigate pressures and improve the state of biodiversity.  This trend has been interpreted as reflecting an increasing awareness of the IAS problem among EU institutions, wildlife managers, scientific institutions, and citizens, but could also indicate that within the EU, the problem with IAS is increasing.  

Thus, in the light of the recent developments regarding the EU regulation on the prevention and management of the introduction and spread of IAS, the new call and the overall novelties introduced within the new LIFE Regulation, are very welcome. In fact the new EU regulation on IAS seeks to address the problem in a comprehensive manner so as to protect native biodiversity and ecosystem services, as well as to minimize and mitigate the human health or economic impacts that these species can have. The IAS legislation now needs only to be formally approved by the Council of Ministers (see details here), and there is a clear need of dedicated financial resources for the implementation of the foreseen types of provision focusing on prevention, early warning and rapid response, and management.

For the 2014 call 132,8 million euro out of a total budget of 404,6 million euro are for nature and biodiversity only, including related governance and information. The deadline for submitting proposals is 16 October 2014. You can find further information, application forms and all official guidance documents here.

Always look on the bright side of LIFE!

Up to € 278 million are available to EU Member States for projects under the seventh LIFE+ call for proposals recently published, and also this year invasive alien species (IAS) are explicitly mentioned within the “Indicative list of themes for LIFE+ Nature and Biodiversity projects”. This means that biological invasions are one of the themes for which the European Commission (EC) would welcome receiving proposals to be co-financed. In fact, two headings are particularly suitable for addressing the problems of IAS: Nature and Biodiversity (NAT) and Information and Communication (INF). For example, according to the NAT application brochure:

 Within the classic LIFE+ Nature projects most of the priorities listed in the EU Biodiversity Strategy to 2020 may be effectively addressed: e.g. invasive alien species through control and eradication in and around Natura 2000 sites

The LIFE brochure on IAS

Under the NAT heading, two different strands exist, which are characterized by different requirements and approaches. Under the LIFE+ Nature strand, it is possible to submit projects for the control and eradication of IAS affecting either the Natura 2000 network or species covered by the Habitats and Birds Directives. Site-related conservation measures for combating IAS can be planned both inside Natura 2000 sites (insofar as they are not recurring actions and they directly benefit the species/habitats targeted by the project) and outside Natura 2000 sites. In the latter case, such measures should be carried out  on strategic spots near or adjacent to a Natura 2000 site to improve the conservation status of the species/habitats target, and to limit or prevent damage within the site. In case of species-related conservation actions for combating IAS (that are not site-related), they can be eligible insofar as they directly benefit the species of the Birds and/or Habitats Directives targeted by the project. Some special requirements must be considered in such a case. For example, applicants must provide guarantees and commitments that the investments made will be sustained in the long-term. The explanatory notes of pag.53 of the application brochure provide some additional indications on the requirements for the range of actions that can be envisaged, e.g. prevention of introductions through the prioritisation and management of pathways, establishment of early warning and rapid eradication system, and management of established IAS. The important is to show solid scientific evidence regarding the added value of the foreseen actions for the Natura 2000 sites/network, and to include an awareness raising component, particularly towards stakeholders involved in the introduction of IAS.

In case of projects aiming at tackling IAS not necessarily in respect to the Natura 2000 network, it is possible to consider submit proposals under the LIFE+ Biodiversity strand, in which case they must have a clear innovative/demonstrative character. For this particular strand, the application brochure welcomes 

projects addressing the threats posed by IAS (1) by preventing the introduction of invasive alien species, in particular by tackling pathways of unintentional introduction, (2) by establishing an early warning and rapid response system and (3) by eradicating or controlling established invasive alien species (in line with the dedicated legislative instrument which is currently under preparation, see here). 

Also in this case, the explanatory notes of pag.57 of the application brochure provide some useful clarification. In fact, also such proposals should include an awareness raising component, in particular towards stakeholders involved in the potential introduction of IAS, and should have measurable biodiversity benefits as one of their main outcomes. Besides, the foreseen actions should be targeted towards the achievement of the 2020 Biodiversity Strategy.

It is also possible to present projects dealing with the IAS issue within the INF heading. In relation to this Information and Communication strand, it is worth mentioning that the LIFE+ programme has developed a logical framework useful to design an effective communication campaign, likely to achieve some measurable impact on the environmental problem targeted (e.g. the impact of IAS) and on the level of awareness (about IAS and their threat), by addressing a specific target audience and gaining the support of specific stakeholders, and by monitoring such impact through specific indicators. More details are included in the LIFE+ INF 2013 Application Guide.

Invasives creeping out of place

To find the first and only "original" remains of a snake in the Canary islands, in the Atlantic sea, we need to go back to the late Miocene, a geological epoch especially renowned for the repeated desiccations of the Mediterranean sea. Paleontologists have found just one vertebra of what was something like a boa living in the archipelago 5-10 million years ago. As far as we know, since then no snakes lived in the Canary islands, at least until the early 2000, when the archipelago has experienced the very unfortunate introduction of the California kingsnake (Lampropeltis californiae). This species, probably escaped or released from captive facilities, is now an important environmental problem in the archipelago due to the enormous social alarm among the population not accustomed to the presence of snakes, and the damage caused to many endemic reptile species, such as the Gran Canaria giant lizard (Gallotia stehlini). To remove this major ecological threat, over 1000 snakes were captured since 2007, and now thanks to the 1 million euro Lampropeltis project supported by the EU through the LIFE+ programme, the authorities expect to set up the conditions for the eradication of the species.

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California kingsnake (striped albino pattern). Photo © Ramón Gallo Barneto

The lucrative trade of species for pet amateurs carries the inherent risk of escape or abandonment of animals kept in captivity, and as a consequence the potential establishment of wild self-sustaining populations of a number of invasive alien species. In fact the California kingsnake is only one of the many species known to have succeeded in getting naturalized outside their native range as a side effect of the pet industry. Another major example among the snakes is the Burmese python (Python molurus bivittatus) in the Everglades, Florida. The spread of this species is a major concern in the region, because it is a predator that can grow over 5 metres long, and as such is able to eat nearly any native animal, possibly even panthers and alligators.

Snakes are often introduced also as cargo stowaway. In this way many species manage to colonise even remote oceanic islands, where they can represent a serious threat to some of the most and unique living creatures of the world. A renowned case of accidental introduction concerns the brown tree snake (Boiga irregularis). Soon after World War II this native of the Solomon islands, northern Australia and Papua New Guinea, was transported as stowaway by military cargos to the island of Guam, Mariana Islands. In this western Pacific island this ecologically disrupting predator is having a dramatic ecological and economic impact. In particular is negatively affecting several species beside having killed off at least 8 of the island’s 11 species of native birds, as well as some indigenous lizards and bats. Now there is a growing concern that the species could take advantage of the frequent aircraft flights from Guam to the Hawaii and make its way to this archipelago in central Pacific, where its ecological and economic impact would be even greater (according to some studies it might cost over 1.7 billion dollar per year if successfully introduced).

Brown Tree Snake. Photo © Daniel O'Brien

Accidental introductions linked to military activities are likely to have occurred also in ancient times: perhaps snakes were used to frighten enemies even during Roman assaults. As suggested for the origin of the viperine snake (Natrix maura) in the Balearic, Spain, some introduced populations of snakes in the Mediterranean islands could be actually linked to such battle related events. Also this snake is having a major ecological impact in terms of loss of indigenous species, and changes in community structures and function. In fact in the Balearic Islands, the introduced viperine snake is known to represent a serious threat for the endangered endemic Mallorcan midwife toad or ferreret (Alytes muletensis) in Mallorca, and was probably involved in the extinction of the species in Menorca.

Other than inflicting ecological harm, non-indigenous snakes can be dangerous to humans, as some species are also poisonous. A typical poisonous snake introduced outside its natural range is the habu (Trimeresurus flavoviridis), a Japanese native viperid introduced in Minnajima, Okinawa Island. Also the brown tree snakes is well known for its venomous bites: in Guam the estimated cost for hospitalisation and intensive care for people affected by snakebite (especially infants) is about 25,000 dollars per year. Along with the ecological damages and the health problems, the brown tree snake can also provoke significant economic impacts, like frequent power outages and damage to the electric lines due to the attitude to crawl along the wires: yearly cost for direct damages and lost productivity is conservatively estimated at 1 million dollars.

Thus, nothing to do with the notorious old rumor, still very popular in countries like Italy, according to which snakes, and particularly vipers, are recurringly broadcasted by helicopters - by either environmentalists or parks authorities - to restore their wild populations. Here the problem for nature conservation professionals is how to prevent the further release or spread of snakes and other harmful alien species outside their natural range, where they clearly represent a key driver of biodiversity loss.