90% of Ibiza, conquered by the horseshoe snake

Palm Horseshoe snakes have become an exponentially growing problem in the Balearic Islands. In 2024, in the Pitiusas Islands—where this species has been classified as invasive since 2013 and, therefore, specific campaigns are carried out to eradicate it—the regional government captured 3,878 snakes, compared to 2,007 the previous year. "Specimens of up to almost two meters have been found in the Islands, although the normal length of an adult snake is between one and one and a half meters with a weight of 500 grams," explains Tomàs Bosch, head of Species Protection at the Ministry of Agriculture, Fisheries and Natural Environment.

In Ibiza, where snakes are currently found on 90% of the island, according to Bosch's estimate, the first recorded sighting dates back to 2003. "It is suspected that they entered the island hidden in flowerpots and olive saplings brought from elsewhere to be planted in villas. During those years, farmers from other regions, such as Andalusia, would take old olive trees due to their low productivity and sell them at cheaper prices as ornamental trees. The demand for this crop in the Balearic Islands grew thanks to the increase in rural hotels and luxury estates that used them for decoration."

The entry of ornamental trees into the Balearic Islands began to be regulated in 2023. The regulations apply to olive, carob, and almond trees with a trunk diameter greater than 40 centimeters. Furthermore, they only allow their entry into Balearic ports during the periods from April 1st to June 15th and from June 15th to June 15th. September to October 15 (inclusive). This prevents the introduction of ornamental trees during the egg-laying season. However, government sources acknowledge that until 2016, the Balearic Government did not carry out "an intensive and powerful control and eradication campaign" in the Pitiusas Islands. In 2016, 145 traps were installed in Ibiza, compared to 1,564 in 2014, according to government data.

Current regulations also require nurseries, commercial establishments selling these trees, and owners to set traps at least between April 1st and October 30th. Mateu Morro, president of Vivers Santa Maria, confirms that they have snake traps, but haven't caught any. Despite complying with the protocol established by the regulations, he believes that "there are fewer snakes in nurseries; they're in forests, pine groves, and ravines."

Meanwhile, a gardener who prefers to remain anonymous believes that companies selling ornamental trees don't want to admit to finding them. "If they catch one, they handle the cage, take the snake out, and nobody knows if they actually caught it or not," he says. He adds that the problem "is very difficult to control because you can't see the snake inside the stump through the small holes in the trunk or in the soil." Furthermore, he points out that in addition to entering the islands through trees, snakes can also travel with imported olive wood. "They shovel it into a container, and you can also catch small snakes that might be there," he says.

And in Mallorca?

Unlike in the Pitiusas Islands, this species is not listed as invasive in Mallorca, so targeted actions are carried out in more sensitive areas, such as the Parc de Llevant, rather than large-scale control campaigns. In 2025, the Balearic Government installed 375 traps on the island. However, the number of horseshoe snakes is increasing, and the regional government has asked the Spanish government to include the snakes (with some exceptions) in the Spanish Catalogue of Invasive Alien Species. "This inclusion would allow the control plans and campaigns carried out in the Pitiusas Islands to also be implemented in Mallorca. If nothing is included, the legal framework is not as robust, and, in general, a comprehensive eradication plan cannot be implemented," warns Bosch. On the other hand, he is pleased that in Menorca, this species "doesn't seem to have arrived yet; there is the white snake, which does not cause serious problems for the native fauna."

What dangers does the snake pose?

The reptile poses a danger to native fauna such as the lizards of the Pitiusas Islands and specific areas of the islands. But it's not only this species that is threatened; it also affects shrews, specifically the grilled rat, a subspecies endemic to Ibiza, and mice. The president of GEN-GOB, Juan Carlos Palermo, points out that years ago, shrew and even rat bones were found in the droppings expelled by owls, something that is "practically no longer seen" where snakes are present. In this regard, he asks: "What will they eat when these animals are gone?"

"Currently, lizards are no longer seen, and neither are shrews," he laments. If species are not declared endangered, "a recovery plan is not usually implemented," Palermo notes. Therefore, he calls for a plan with clear objectives to save the lizard.