January 16, 2021

The Ibiza lizard, a unique species in the world, threatened by invasive snakes

The lizard of Ibiza and Formentera is a unique reptile on the planet with more than twenty different subspecies. For thirteen years, three species of snake that arrived from the Peninsula through the olive trees for nurseries have been decimating their populations. Experts believe that the Ibiza lizard may disappear in twenty years.

The endemic lizard of Ibiza and Formentera (Podarcis pytiusensis) was already present on both islands before man made his appearance on them, about 4,000 years ago. Many animal species have passed through the Pitiusas over the centuries, but one of the few that have always remained there have been its popular lizards, already converted into a symbol of island identity. Now he is in danger for the first time.

The cause of this situation is the invasion of snakes from the Peninsula that the island has suffered for more than a decade. Then, shipments of olive trees arrived by boat destined for the island’s nurseries became, without knowing it, a deadly weapon for the lizard.

These olive trees had stowaways on board: snakes of various species, but especially horseshoe and ladder snakes, common in the Peninsula but never existed in Ibiza and Formentera. They are, therefore, invasive species that compete with the lizard for the same foods and habitats. The popular Ibizan reptile has the upper hand, because until now it had no predators of this level and it has no weapons with which to defend itself.

Ibiza lizard. Source: daysedge productions

Since the local institutions reacted in 2007 and placed the first traps against snakes, thousands of them have been caught, but it is a plague that advances unstoppably, also favored by its exponential reproduction capacity.

They have even invaded the islets, which they swim to, endangering the important subspecies of lizard that exist there. There are more than twenty subspecies, practically one for each islet, all characterized by showy colorations, which differ in each case and thus allow them to be quickly identified.

Lizards have inhabited the island since before man. Photo: Pinterest

Like the finches of the Galapagos

“Before the arrival of man, Eivissa and Formentera had a flora and fauna very different from the current one and the only animal that has survived is the lizard, it is the only truly indigenous one we have. Everyone else has come with the man. Within the world context it is a similar example, within the evolution and adaptation of species, to that of the Galapagos finches that Darwin studied. In each of these Pacific islands there is a different species of finch, with the Pitiusan lizards it happens the same. It is a very spectacular evolutionary and adaptive example”, Declared the Ibizan biologist Antònia Maria Cirer, author of outstanding studies on the species.

The biologist is pessimistic about the situation: “In twenty years the lizard could disappear if the snakes are not eradicated, because they have a brutal reproductive potential. Populations are growing at an exponential rate. Either act fast or if not, this has a very bad omen ”.

Subspecies corresponding to one of the islets of Ibiza. Photo: José Miguel L. Romero

The island has called out against the invading snakes. On one side, the public administrations, which remained quite inactive in the initial moments of the invasion (when it could be stopped), now plan to multiply the number of traps. In the next three years, 2,000 of them will be installed, distributed in houses and private farms, to try to capture as many as possible. It is an initiative of the Ministry of the Environment of the Balearic Government.

Mass distribution of anti-snake traps

The veterinarian of the Consorci per a la Recuperació de la Fauna Salvatge (Cofib) Víctor Colomar, points out that this initiative does not really aspire to eradicate the plague of invasive snakes from Ibiza, “something that is not possible in three years, nor surely in many more ».

The objective, he adds, is “to achieve a sufficiently low density of snakes that allows the survival of the Ibizan lizard.

Since the work to capture these snakes began in Ibiza, in 2007, Around 7,000 have been exterminated “and now we are trying to give this figure a good boost,” Colomar said.

In 2020, 875 specimens were caught on the island of Ibiza and 494 on that of Formentera, according to the figures provided by the Balearic Government.

One of the snakes caught last year. Photo: Diario de Ibiza

But, on the other hand, various environmental and cultural groups on the island have also got down to work and have launched a public campaign to complement institutional action.

These groups remember that the Pitiusan lizard (sargantana) “constitutes a world-class biological heritage that must be conserved by the administrations, providing the necessary resources”.

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