Conservationists in the Balearic Islands have received what they describe as 'irrefutable proof' of a significant new threat to native wildlife, following the capture of a video showing a horseshoe whip snake swimming between Ibiza and a nearby islet. The footage, filmed in April 2024, depicts the invasive snake navigating the 450-metre stretch of turquoise water separating the east coast of Ibiza from the islet of Santa Eulària. This discovery confirms long-held suspicions among Spanish researchers and wildlife experts that the snakes are capable of colonising new, previously inaccessible areas, posing an existential threat to the critically endangered Ibiza wall lizard.
The horseshoe whip snake (Hemorrhois hippocrepis) is not native to the Balearics. It is believed to have been introduced to the islands inadvertently through the import of mature olive trees from mainland Spain, primarily for landscaping purposes in villas and tourist resorts. Since their arrival, the snake population has proliferated rapidly, particularly on Ibiza, where they have already decimated local lizard populations in many areas. The ability of these snakes to swim to offshore islets significantly expands their potential range and the scale of the ecological damage they can inflict.
The Ibiza wall lizard (Podarcis pityusensis) is an endemic species, meaning it is found nowhere else in the world. It plays a crucial role in the island's ecosystem and is a protected species under European law. Its vibrant green and blue colouration makes it a distinctive part of the Balearic natural heritage, and it is a popular sight for tourists and residents alike. The insatiable appetite of the horseshoe whip snake for these lizards has already led to drastic declines in their numbers on the main island, and the threat of the snakes reaching isolated lizard populations on smaller islets is a major concern for biodiversity.
Wildlife experts have described the situation as a 'tragedy' for the islands' unique biodiversity. Efforts to control the snake population have been ongoing, primarily through trapping programmes. However, the discovery of their swimming capabilities underscores the immense challenge in containing their spread. The implications extend beyond the immediate threat to the lizards, as the loss of a key prey species can have cascading effects throughout the delicate island ecosystem.
The Balearic government, in collaboration with environmental organisations, has been implementing measures to mitigate the impact of the invasive snakes. These include public awareness campaigns and increased efforts to intercept and remove snakes. However, the sheer scale of the problem and the snakes' adaptability mean that a comprehensive and sustained long-term strategy will be essential to protect the future of the Ibiza wall lizard and the broader ecological balance of the Balearic Islands.