In addition to the threat of snakes snakesIn addition to the threat of snakes, the Balearic Government has announced that this year it will invite tenders for a rat extermination project on the islets of Tagomago, Es Vedrà and Es Vedranell, in Ibiza, and in s’Espalmador, in Formentera.
This initiative seeks to improve the survival of seabird species that nest in the area, such as the Balearic shearwater, the Balearic shearwateran endemic species, as well as being part of the efforts to protect the Pitiusa lizard.
Although it is more socially normalized, the rat is “a species that is also classified as exotic, invasive. People see a mouse or a rat and are not so shocked,” explains the manager of the Consortium for Fauna Recovery of the Balearic Islands(COFIB), Miquel Puig, to La Voz de Ibiza. However, it is an animal that is not natural to these lands. “Rats have been among us for centuries, although they should not be here. We have introduced them, involuntarily, as in many other areas of the world, and we are no exception. It is a species that is not natural in the islets of Pitiusas, it is not its area of distribution,” he adds.
In this context, while on some islets a kind of “balance between flora, local fauna and rats” has been achieved, on others the overpopulation of these rodents “causes other species, including sargantana, flora or seabirds, to have fewer resources, suffer more disturbance and have conservation problems caused by the rats”.
An unexpected competitor
Although a rat will not directly eat a lizard, it is an important factor in the risk of extinction of this emblematic animal of Ibiza and Formentera. “The danger of rats is that they can eat a sargantana egg or a seabird egg or even a chick of some protected species of bird. Or it will simply occupy the territory and compete for resources, which in the end is perhaps not as direct a statement as in the case of ophidians, but it is a competing species and a species that also gives many problems to the sargantana,” Puig explained to La Voz de Ibiza. Therefore, the possibility arose, with funding from the European Project, “to undertake the deratization of these emblematic islets: Tagomago, Es Vedrà, Es Vedranell and s‘Espalmador, which are perhaps the largest and best known islets we have in Ibiza and Formentera, to try to eradicate rodents”. The bidding period ended this week. “There are a number of companies that have already presented themselves, the Contracting Committee will have to evaluate the offers and a company will be appointed. This is scheduled to be done throughout 2025,” says Puig. In any case, the COFIB manager clarified that this process of deratization of the islets “would begin at the end of summer to avoid disturbing the seabirds that breed. Obviously it is taken into account to cause the least possible harm to wildlife species. That is why the idea is to start that at the end of summer, August or September, also depending on other climatic and environmental factors”. The rat extermination method included in the contract specifications is by means of specific rodent poisons. “These substances have been shown not to affect sargantanas,” Puig explains. In addition, the active ingredient is distributed in specific primers so that other species cannot access them.
Research
Two British scientists conducted an investigation entitled “Regenerated lizard tails as a possible indicator of predation of Podarcis pityusensis by rats”. The main thesis of the study was that the regenerated tails of lizards are a clear indication that they are being attacked by rodents.
Invasive flora
Likewise, on the islet of s’Espardell, in Formentera, an intervention will be carried out to eradicate invasive flora, where 1.5 hectares of noon flower, 500 prickly pears, several dozens of pitas and about 70 square meters of lion’s claw have been detected.
