In recent years, the overpopulation of snake overpopulation has taken over Ibiza and the pitiüsa lizard(Podarcis pityusensis) is facing extinction. However, a new alert is being raised about this environmental risk: they have begun to colonize the islets.
This has been warned by the Department of Agriculture, Fisheries and Natural Environment of the Balearic Government, which this week has launched a video to raise awareness among both the local population and tourists about the delicate situation of the lizard of Ibiza and Formentera. This migration from the main island to the islets by the snake began to be detected last year, as explained to La Voz de Ibiza the manager of the Consortium for Fauna Recovery of the Balearic Islands(COFIB), Miquel Puig. https://www.youtube.com/watch?v=cQvgWIIT25A “The colonization of what are the Pitiusas islands dates from 2003-2004, especially in Ibiza which was the first site. This invasion was growing as the first years of this century passed. But last year there were the first traps and first captures in the islets peripheral to the island of Ibiza,” he explains. For this reason, inspections have been carried out on all the islets. “Fortunately, we have not found snakes on all of them. In some we have found and trapped snakes, in others we have seen signs of the presence of snakes, such as a drop in the population of sargantana, that is, that the densities of sargantana have dropped a lot; or you can find a molt, which is the skin that snakes shed when they grow, “explains the specialist. Thus, COIF has detected three areas where “we have the most serious or complicatedissues” due to the presence of the snake: Murada, Santa Eulalia and S’illot de s’Or
. “ These three islands or islets are the most dangerous, where we have had more problems, with more snake captures,” said Puig.
How to reach the islets
The snake, mainly the horseshoe snake, which is the most problematic in the Pitiusas, “is a very good swimmer. It is an animal that does not mind swimming and can cross relatively large expanses of water, open sea,” according to the COFIB manager. Although it is unknown why it started this migration, COIF believes that it could have been “accidentally falling into the water” or in search of “food or resources that are thrown into the sea and cross these small stretches of water between the main island of Ibiza and these small islets”.
In these small areas of reduced dimensions, where the population density of lizards is high, the risk of extinction is even higher. “Sargantanas are found on that islet without natural predators, they are found without competitors. Therefore, they occupy the entire surface or all the useful space of the islet. Then, when a predator arrives, it finds that it has no competitor either, it has no other super predator to control the snake population and, therefore, two species that have never coexisted come into contact: the horseshoe snake and the Pitiusa sargantana,” explains Puig. Thus, the only vertebrates available on these islets are lizards, in addition to some seabird. ”
Therefore, the snake, obviously, as a food resource, has little to choose from. So, it preys on the sargantana. And the sargantana, in turn, has little space in which to flee or hide. “.
High risk of extinction
In this context, the lizards are practically cornered in a hostile and unfavorable scenario. “This problem is generated and can lead to the local extinction of the sargantana, if nothing is done. The risk on the islets is very high,” he warns. For this reason, “visual surveys are carried out in these areas, that is, these islets are visited with a boat that has also been purchased with European funds. The island is divided into small areas and is systematically visited to make a first sighting, a census, that is, we try to see what number of sargantanas there are and compare with previous censuses”.
“If we consider that the sargantana population is the same or better than the previous census, you are a little calm. The moment we have any indication, we put some traps on these islets to see if any animal falls. If there is clear evidence of colonization of these islets by ophidians, or if we see one directly, then we do systematic trapping. We call it intensive trapping and we try, obviously, to control the snake population and, if possible, eradicate them all, which is the idea,” explains Puig.
The collaboration of neighbors
Through the Consortium for the Recovery of the Fauna of the Balearic Islands, under the General Directorate of Natural Environment and Forest Management, citizens are urged to report the presence of snakes in the application Línea Verde COFIB – Invasive Species (www.lineaverdecofib.es). “Citizen collaboration is basic.
Our work has little meaning without society behind it. In the end, they are usually the first alerters, they are usually the people who give us clues, who guide us, who call us or who indicate us. And, obviously, we have found a very good response from the general part of the Pitiusa society”, says Puig.
“We are always grateful and I take this opportunity to thank the citizens for their collaboration, the notices they give us, the support and, above all, the impulse. It is satisfying to be able to count on the help of all the people and it makes our work easier,” he adds. In addition, he remarks that the lizard is a “very emblematic animal for the whole autonomous community and, especially for the Pitiusas, very dear, very valued. And, on the other hand, the snake, obviously, is not so much. It is not an animal that has such a good reputation, unfortunately”. “The snake does not have a good press. I always say the same thing: what’s its fault? It has simply arrived here and fulfills its vital function in the ecosystem, which is to live, survive and reproduce,” concluded the COFIB manager.
