A new scientific study has raised fresh concerns about Ibiza's growing invasive snake problem, finding that the spread of the horseshoe whip snake is accelerating and that native lizard populations are disappearing far more quickly in areas newly colonised by the predator.

The horseshoe whip snake (Hemorrhois hippocrepis) is not native to Ibiza. Researchers believe it arrived on the island in the early 2000s, most likely hidden among imported ornamental olive trees brought from mainland Spain. Since then, the species has expanded across much of Ibiza, creating one of the island's most serious threats to native biodiversity.

The latest research, published in Proceedings of the Royal Society B, reconstructs the invasion using around two decades of observations and field data. The researchers found that the relationship between the invasive predator and its native prey has become increasingly concerning as the snake continues to establish itself in new parts of the island.

From Imported Olive Trees to an Island-Wide Invasion

The story began more than 20 years ago.

Horseshoe whip snakes were first recorded in Ibiza in 2003. Researchers believe the most likely route of introduction was the movement of mature ornamental olive trees from mainland Spain. The trees, often transported for landscaping projects, can contain hollows and cavities where snakes or eggs can remain hidden during transport.

Once established, the snakes encountered an ecosystem that had evolved without this type of large terrestrial predator.

The result has been a rapid expansion. Research published earlier this year found that horseshoe whip snakes now occupy more than 90% of Ibiza.

The Native Lizard at the Centre of the Crisis

One of the species most affected is the Ibiza wall lizard, or Pityusan wall lizard (Podarcis pityusensis).

The lizard is endemic to the Pityusic Islands, meaning it is naturally found in Ibiza, Formentera and their surrounding islets. It is also considered an important keystone species within the local ecosystem and was reclassified as Endangered by the IUCN in 2022.

The problem is particularly severe because the lizard makes up more than half of the horseshoe whip snake's diet within its invasive range in Ibiza.

For an island species that evolved without this predator, the arrival of the snake has created a completely new ecological pressure.

The Time Between Snake Arrival and Lizard Loss Is Shrinking

One of the most concerning findings from the latest research is how quickly the impact appears to be occurring.

Researchers found that the interval between the arrival of horseshoe whip snakes and the local disappearance of lizard populations has shortened from more than 10 years in earlier-invaded areas to approximately three years in more recently invaded areas.

That suggests the ecological impact is not simply continuing at the same pace. The invasion is becoming increasingly efficient at reaching new areas and affecting vulnerable lizard populations.

The researchers also found evidence that natural snake movement is not the only factor driving the expansion. Human activity can help transport snakes into new areas, creating additional opportunities for the species to establish itself.

The Snakes Can Even Swim Between Islands

The threat extends beyond Ibiza itself.

A separate study published in Ecology in 2026 documented horseshoe whip snakes swimming between Ibiza and nearby islets. Researchers found that the snakes were capable of crossing stretches of sea in search of new territory and prey.

The discovery is particularly concerning because the small offshore islets have historically provided important refuges for native lizard populations.

Researchers documented the disappearance of local lizard populations on around 10 islets after the snakes arrived, highlighting how quickly an isolated ecosystem can be transformed when a new predator reaches it.

More Than 12,000 Snakes Have Been Removed

Authorities and conservation teams have been attempting to control the invasion for years.

More than 12,000 invasive snakes had been removed through control efforts since 2016, according to the 2026 Ecology research. Despite these efforts, the horseshoe whip snake continues to expand across Ibiza.

The scale of the challenge has made complete eradication increasingly difficult. Conservation efforts are therefore focused on slowing the spread, protecting remaining lizard populations and preventing the snakes from establishing new populations on vulnerable islets.

A Warning About Human-Made Introductions

The Ibiza snake crisis is also a reminder of how easily human activity can alter an island ecosystem.

What began with the movement of ornamental trees has developed into a long-term conservation problem affecting species found nowhere outside the Pityusic Islands. The case demonstrates the risks associated with transporting mature plants and other materials between ecosystems, particularly when they can harbour animals, eggs or other organisms.

For Ibiza, the consequences are no longer theoretical. An invasive predator has established itself across most of the island, while an endemic species is facing an increasingly severe decline.

A Threat to Ibiza's Natural Heritage

The horseshoe whip snake is not venomous and is not considered a significant danger to people. The concern is ecological.

For residents and visitors, the story is ultimately about protecting a part of Ibiza that is just as distinctive as its beaches, coastline and cultural heritage. The Pityusan wall lizard has been part of the islands' natural environment for thousands of years, and scientists are now racing to understand whether remaining populations can survive the continuing spread of an introduced predator.

The latest research provides a clearer picture of how quickly that change is happening. It also highlights the importance of early detection, controlling human-assisted spread and protecting the remaining strongholds of Ibiza's endemic wildlife.

For an island whose identity is so closely connected to its unique Mediterranean landscape, the fight to preserve that natural heritage is becoming increasingly urgent.