Ibiza’s ecosystem is facing an unexpected challenge that has left scientists both fascinated and concerned. In recent years, an invasive species—the horseshoe whip snake (Hemorrhois hippocrepis)—has spread across the island, disrupting its delicate biodiversity. But what has truly astonished researchers is that these snakes are now swimming, crossing stretches of seawater to reach small islets that were once safe havens for the Ibiza wall lizard (Podarcis pityusensis), a species found nowhere else in the world. This phenomenon is not just unusual—it’s a potential ecological disaster.
Originally from North Africa and the Iberian Peninsula, these reptiles have successfully colonised Ibiza, adapting in ways that have surprised scientists. While they are harmless to humans, their growing numbers pose a serious threat to the Ibiza wall lizard (Podarcis pityusensis), a species found only in the Pityusic Islands and a true emblem of Ibiza and Formentera.
But what has truly alarmed experts is their newfound ability to swim long distances, reaching small islets that were once safe havens for the endangered lizard.
Snakes that swim? A shocking discovery
Until recently, researchers assumed that the reptiles spotted on islets had arrived there by accident—perhaps hidden in boats or floating on driftwood. However, recent evidence confirms that they are actively swimming from Ibiza to nearby islets in search of new territory.
Herpetologist and zoology professor Valentín Pérez Mellado describes this as “absolutely astonishing”.
“The horseshoe whip snake is a species that typically inhabits the mainland, and there had never been reports of it actively crossing stretches of seawater. Yet, here in Ibiza, we are witnessing this incredible phenomenon,” Pérez Mellado explained in an interview with Diario de Ibiza.
This adaptation is deeply concerning because many offshore islets around Ibiza hold genetically unique lizard colonies that have existed in isolation for thousands of years. Now, with snakes reaching these remote locations, the survival of these endemic reptiles is in serious jeopardy.
Why are these reptiles thriving in Ibiza?
The horseshoe whip snake was first detected in Ibiza in the early 2000s, likely introduced unintentionally through shipments of olive trees and ornamental plants from mainland Spain. With no natural predators on the island and abundant prey, they have flourished, rapidly increasing in number.
Scientists have noted several alarming behavioural changes in these reptiles:
- Growing in size: specimens found in Ibiza tend to be larger than their counterparts in mainland Spain and North Africa.
- A diet focused on lizards: their hunting instincts have adapted to prioritise feeding on the Ibiza wall lizard, consuming them at an alarming rate.
- Developing strong swimming skills: their ability to travel across open seawater has made them even harder to contain.
“We never expected these reptiles to actively swim in search of food. It’s an unexpected and deeply concerning adaptation,” says Víctor Colomar, coordinator of COFIB (the Consortium for the Protection of Wildlife in the Balearic Islands) for Ibiza and Formentera.
A threat to Ibiza’s wildlife
For many visitors, the Ibiza wall lizard is an essential part of the island’s identity—frequently seen darting across stone walls and even featured on souvenirs, artwork, and tourism campaigns. However, this symbol of Ibiza’s biodiversity is now at serious risk.
If these reptilian invaders continue to spread, the impact could be catastrophic:
- The extinction of endemic lizards: the Ibiza wall lizard, found nowhere else in the world, could disappear within decades.
- Disrupting the island’s ecosystem: the reduction in lizard populations could lead to imbalances in insect numbers and affect bird species that rely on them for food.
- Changing plant life dynamics: lizards play a role in seed dispersal, and their disappearance could alter vegetation patterns.
Can the problem be controlled?
Eradicating these reptiles from Ibiza is no longer a realistic possibility, but scientists are exploring ways to limit their spread and reduce their impact. Some of the proposed solutions include:
- Capturing and relocating individuals to slow their expansion.
- Creating protected areas where lizard populations can recover without interference.
- Stricter regulations on the importation of plants and trees, which have been a major entry point for new snakes.
According to Pérez Mellado, “If conservation efforts are ignored in favour of free trade, we will need to rethink our priorities as a society. Otherwise, we risk losing one of Ibiza’s most iconic species forever.”
What can tourists do to help?
If you’re planning a trip to Ibiza and want to contribute to conservation efforts, here’s how you can help:
- Be mindful of the environment when hiking or exploring the island’s natural spaces.
- Support local conservation projects by visiting nature reserves or eco-tourism initiatives.
- Report sightings of unusual wildlife to local authorities to help monitor population changes.
Ibiza’s stunning landscapes and unique wildlife are part of what makes it such a special destination. While these snakes may not pose a danger to people, their growing presence is a real threat to the island’s fragile ecosystem. Raising awareness and supporting conservation efforts could be the key to protecting Ibiza’s biodiversity for future generations.
A changing ecosystem in Ibiza
The presence of snakes in Ibiza is not new, but their recent adaptations—particularly their ability to swim long distances—have scientists deeply concerned. What started as an accidental introduction has turned into an ecological challenge, threatening one of the island’s most emblematic species.
For now, experts agree that completely eliminating these reptiles from Ibiza is impossible, but urgent measures must be taken to control their spread and protect the island’s unique biodiversity. If nothing is done, the Ibiza wall lizard could vanish forever, altering the delicate balance of nature that makes this island so extraordinary.
Key takeaways for visitors:
- Snakes in Ibiza are non-venomous but pose a serious threat to local wildlife.
- Their ability to swim is a surprising adaptation that is endangering the Ibiza wall lizard.
- Conservationists are working to control their numbers, but challenges remain.
- Tourists can help by supporting conservation efforts and being mindful of the local ecosystem.
