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!

Marine mammals on their way to new seas

White whales and grey seals have found a new home in the Black sea. In fact one of the largest organism introduced by humans  outside its natural range is the beluga. This beautiful marine mammal, not to be confused with the homonymous European sturgeon, is also known as white whale (the word beluga derives from white, in Russian). It should be remarked that the name is a bit misleading, as the beluga is a toothed cetacean and as such is rather a dolphin than a whale. Like other dolphins, belugas have been introduced in the Black Sea as a consequence of escapes and/or releases from coastal dolphinaria and oceanaria (where animals are kept in near-shore open-air pens which do not adequately prevent escapes of captive animals into the sea - see also a previous article here). The story of the beluga whale in the Black Sea started in the early 1990s, when one individual captured in Sakhalin Bay, Russia, was transferred to Crimea, Ukraine, where it was immediately released, or escaped, into the sea (actually, it was recaptured once, and then soon after released/escaped again). Another beluga was indeed released (or escaped) at the same time and place, and was also observed and reported in the wild several times. The two beluga whales were often observed in the wild near the Turkish, Romanian, Bulgarian and Ukrainian coasts, but their current status is unknown (more details on Birkun 2002; Reeves & Notarbartolo di Sciara 2006).

Interestingly the list of marine mammals spontaneously released in the Black Sea includes also other species, like the grey seal, the northern fur seal, the Steller sea lion, the harbour seal, the Caspian seal and, possibly, some other pinnipeds. Such cases of escape/release have been known in the Black Sea since the early 1980s, but occurred also in other regions. For example, the escape of a sea lion from an aquarium to the wild is also known in the Canary Islands. Otherwise three sea lions escaped from the Prague zoo after the severe flood of 2002, they were all recaptured within a few days, but one of them managed to roam for hundreds of kilometers along the Elbe river from Prague to Dresden, before being recaptured.

Harbour seals at Copenhagen zoo ©  Photo: Vibe Kjaedegaard

The number of animals escaped and/or released in the Black Sea is unknown (but is likely around a few tens), and also the actual fate and impact of the relevant species is uncertain. It is likely that the marine mammals escaped from dolphinaria and similar facilities did never lead to established populations, however it is known that species may have a very long lag phase before getting naturalised, or showing any impact. Of course this does not mean that in the meantime they do not affect the hosting ecosystem. This is especially true in the case of long-living organisms, in which case also a single animal can have a major impact on the ecosystem. For example there is some concern that they could be a source of infections circulating in dolphinaria. In any case such introductions show that the extent of the problem can be unexpectedly large, both in terms of size of animals moved from place to place, and in terms of size of ecosystem affected.

On the other hand, a recent paper by Gladilina & colleagues (2013) highlighted some positive aspect related to the introduction of an exotic grey seal in the Black Sea. The presence of this North Atlantic species has been regularly recorded in the north-east Black Sea since 2001. Its introduction is considered the consequence of an escape from captivity. Surprisingly, no major conflicts have been recorded with fisheries, as fishermen seem to tolerate the presence of this mammal despite the little damage to fishing gears. In any case, the seal seems perfectly adapted to the new environment. This led Gladilina and colleagues to assume that the long term survival of the grey seal in the Black Sea might indicate the possibility of successful re-colonization of the area by monk seals, the only extant aboriginal pinniped in the Black Sea, disappeared at the end of the 20th Century. Hopefully this will be compatible with the growing "novel" community of marine mammals.

A new code for preventing animal escapes from zoos

Himalayan porcupines and Egyptian fruit bats do not belong to the European fauna, yet a few years ago they were well established in the wild, respectively in Devon (UK) and in the Canary islands. Wildlife managers decided to remove them to mitigate their impact on the new environment. Nevertheless, the problem could be easily prevented, because the introduction of the two species was probably a consequence of zoo escapes.

Specific and comprehensive analysis regarding invasive alien species (IAS) originated by escapes and/or releases from zoological gardens and aquaria in Europe are lacking, but there are evidences of some IAS populations still thriving and clearly originating from such pathways (even though in terms of relative risk, zoos and aquaria have a limited responsibility compared to other pathways i.e. pet trade, hunting, horticulture, etc.). A famous case is the one of the ruddy duck, a species of North American origin, which represents a major threat to the European white-headed duck, and is now being targeted by costly management programs. Another famous “escape” is the one of the tropical alga Caulerpa taxifolia unintentionally introduced from a public aquarium into the Mediterranean Sea. There is also an episode regarding the transmission of disease, like in the case of the deadly amphibian fungus Batrachochytrium dendrobatidis (Bd) accidentally introduced within the endangered population of the Mallorcan midwife toad (although before Bd was identified as a pathogen, and relevant screening methods were established). Surprisingly, there are also several records of marine mammals (including even beluga whales and sea lions) introduced from coastal dolphinaria and oceanaria, particularly in the Black Sea.

In Poland the Canada goose was unintentionally introduced also through escapes from a local zoo. Photo © Vibe Kjaedegaard

The identification of pathways and the implementation of best practices and voluntary measures to prevent the threats posed by IAS are currently recognised as critical issues in relation to the European policy on IAS. On the other hand, modern zoos are privileged allies of conservationists for the fundamental role they play on biodiversity conservation programs and related awareness raising activities (it is estimated that over 140 million people visit European zoos every year). For this reason, the Bern Convention and the Invasive Species Specialist Group (ISSG) of the IUCN, in collaboration with the European Association of Zoos and Aquaria (EAZA) have developed the European Code of Conduct for Zoological Gardens and Aquaria on Invasive Alien Species.

The publication in English (link updated on 27/11/2016)

The objective of this document is to provide guidance to zoological gardens and aquaria to strengthen their role for biodiversity conservation in Europe, by contributing to mitigate the problems related to the spread of IAS. This should be done through the following measures:

• Prevent the introduction and spread of IAS and related pathogens and diseases;
• Promote the need to raise awareness on biological invasions;
• Support IAS related research projects and other relevant conservation initiatives.

In line with the Convention on Biological Diversity (CBD) targets for 2020, as well as the EU biodiversity strategy to 2020, the code includes five main recommendations:

1. Adopt effective preventative measures to avoid unintentional introduction and spread of IAS;
2. Take into account the risks of IAS introductions in all wildlife and habitat management projects;
3. Proactively engage in awareness raising and outreach activities focusing on IAS and their impacts;
4. Adopt best practices for supporting early warning and rapid response system for IAS;
5. Be aware of all relevant regulations concerning zoological gardens and aquaria and IAS

The code - which includes a description of measure to implement the five recommendations above - has been formally approved at the last Standing Committee meeting of the Bern Convention on 30 November 2012. At the same meeting, with the aim of ensuring responsible and proactive policies and applying these in a coherent manner across Europe, the Standing Committee praised the innovative approach of such voluntary instrument, and adopted the Recommendation No.161 (2012). The aim is to invite all Bern Convention parties to implement the code, by drawing up their own national codes of conduct based on the European version, and by collaborating with zoological gardens and aquaria in implementing good practices aimed at preventing the spread of invasive alien species.

Another major achievement of the new code has been the formal acknowledgement received by the recent 11th Conference of the Parties of the CBD held at Hyderabad (India, 8-19 October 2012) which in its Decision XI/28. Invasive alien species:

“welcomes the development of voluntary codes of conduct on these separate pathways, such as the “Code of conduct on zoological gardens and aquaria and invasive species” developed by the Bern Convention, the IUCN Invasive Species Specialist Group and the European Association of Zoos and Aquaria, and requests the Executive Secretary to compile information and to work with experts to avoid and/or minimize the risks particular to these separate pathways”

Shutting the stable door before the horse bolts.
Drawing © Riccardo Scalera