The snakes that have spread across Ibiza and Formentera over the past two decades are now officially considered an invasive species throughout the Balearic Islands, giving the authorities stronger legal tools to stop them reaching new territory.
Spain’s official state gazette, the BOE, published the change to the national catalogue of invasive alien species on Tuesday, following a request made by the Balearic government a year ago. Until now, introduced snakes of the colubrid family were only listed as invasive in Ibiza and Formentera and on uninhabited islets. The new listing covers the entire archipelago, with exceptions for the few species that are native to Mallorca and Menorca.
Why it matters
Being on the catalogue places a species under a specific legal regime for prevention, control and, where possible, eradication. According to the Balearic environment department, the change provides legal backing for the trapping already under way and for a new campaign to keep the snakes out of sensitive areas of Mallorca and its islets, home to vulnerable species such as the Balearic lizard and the ferreret, a tiny native toad.
Ibiza’s cautionary tale
Ibiza shows what is at stake. The horseshoe whip snake is believed to have arrived about 20 years ago, hidden in ornamental olive trees imported from mainland Spain. A study led by the CREAF research centre and published this year found that it now occupies around 90% of the island.
Its main victim is the Pitiusan lizard, the small, often brightly coloured reptile found only in Ibiza, Formentera and their islets, and a symbol of the islands. Lizard populations have collapsed across much of Ibiza and have disappeared from about a dozen islets. On Illa de Santa Eulària, researchers counted 72 lizards in 2016, three in 2023 and none in 2025.
Thousands caught every year
Trapping now runs all year round. According to figures presented at the Consell d’Eivissa this spring, more than 3,600 snakes were caught in Ibiza in 2025, from nearly 2,000 traps, and almost 900 in Formentera. The 2026 campaign has up to 13 specialists, with a focus on the west of the island and the coast.
Anyone who spots a snake can report it through the Balearic government’s Línea Verde app.
