Soon No More Lizards? How the Horseshoe Snake Is Hollowing Out Ibiza's Smallest Islands

Soon No More Lizards? How the Horseshoe Snake Is Hollowing Out Ibiza's Smallest Islands

The central question: How do you protect an island world when a swimming invader comes ashore?

On an early morning in Palma, on the Passeig Marítim, the coffee smells strong, motorcycles whir by and holiday-brochure sellers set up their stands. Such everyday scenes stand in stark contrast to what researchers observe on Ibiza: a snake, not originally native, is spreading and eating through the small territories of endemic lizards.

The Centre de Recerca Ecològica i Aplicacions Forestals (CREAF) reports in a study published in Ecology that the so-called horseshoe snake now occupies almost 90 percent of Ibiza’s area and can even reach small neighboring islets. The species apparently arrived about two decades ago with imported ornamental olive trees and has now also been recorded on Formentera, a trend explained in Why Snakes Are Appearing More Often in Mallorca Now — Danger, Causes and What We Should Do.

One case study makes this clear: on a small islet near Santa Eulària, researchers set up traps over two years and captured 58 snakes. Parallel transect counts show a dramatic collapse of the Pityus lizard: in 2016 teams still counted 72 individuals in the comparison sections, in 2023 only three remained, and in 2025 none appeared at all. These numbers are not distant statistics — they represent concrete local population losses.

Critical analysis: where does the system fail? In short: in prevention, monitoring and political urgency. The import of plants as a gateway for invasive animals is not a new problem — but in this case trade laid a biological time bomb for years. Authorities on Mallorca already reacted with an import ban on olive trees; yet bans alone are not enough when controls are lacking, illegal transports continue, or established populations are not dealt with consistently.

Another weak point: many small islands are hard to monitor. Rangers cannot search every rock every day. For the research teams this means setting traps and intensive mapping — expensive and personnel‑intensive. Political decision‑makers often see short‑term costs rather than the long‑term bill: loss of biodiversity, disappearing endemic colors and patterns that are first and foremost part of the island identity. Similar issues have prompted warnings for local islets such as the Malgrats in Alarm at the Malgrats: Invasive Snakes Threaten the Sargantana.

What is missing in public discourse: a clear debate about priorities and risk assessment. It is not just about a pretty reptile; it is about functioning ecosystems, about the disappearance of genetic diversity and about a question that is emotionally charged in the Balearics: what landscape do we want to have tomorrow? So far technical reports about captured snakes dominate; the bigger questions about funding for monitoring, long‑term management plans and prevention chains are asked too rarely.

Everyday scene from Mallorca: at the Mercat de l’Olivar vendors routinely offer small olive trees in pots — compact, ideal for a city balcony. Customers ask for frost‑hard varieties, not realizing that the same plant shipments once brought in animals. A neighbor in the quarter says she saw a snake at night on the finca next door years ago; the reaction then was “doesn’t happen often.” Such apathy helps the invaders.

Concrete solutions: first, targeted checks at points of entry and stricter phytosanitary inspections for ornamental plant imports. Second, a comprehensive monitoring network with local volunteers, ranger pairs and coordinated data collection — citizen science can help if data are passed on in a standardized way. Third, rapid emergency interventions on islets: if a few snakes are enough to wipe out a population, the reaction mechanism must work — traps, targeted removal, follow‑up checks. Fourth, create protected refuges: for particularly unique subpopulations of the Pityus lizard, temporary ex‑situ programs and secured sanctuaries could be sensible. Fifth, information campaigns: buyers of plants should know the risks involved; garden centers and ports must be trained.

The challenges are political as well as practical. Funding for conservation measures is often approved from budgets that solve short‑term problems but do not secure long‑term protection. A coordinated approach by the island administrations is needed, clear priorities — and the willingness to not only decree unpopular measures such as restrictions on plant imports, but to permanently enforce them.

Pointed conclusion: if we continue to watch, we will lose not only lizards; we will lose pieces of island history, colors and behaviors that exist nowhere else. The horseshoe snake is not a local nuisance, but a warning sign for the failure of prevention and coordination. In the Balearics it is currently being decided whether islands remain mere tourist backdrops or living biotopes with their own future.

Whoever boards the ferry from Palma to Ibiza tomorrow morning should take in the coffee aroma and the sound of the sea even more intensely: we can still turn things around — but only if politics, research and society show the necessary resolve.