The invasive snakes already occupy 90% of Ibiza and threaten to extinguish the Balearic lizard
The research confirms that these snakes are capable of swimming in the sea and are also extirpating populations on nearby islets
PalmaA study led by the Centre for Ecological Research and Forestry Applications (Creaf) warns that the horseshoe whip snake (Hemorrhois hippocrepis), an invasive snake that already occupies 90% of Ibiza and can swim to islets, "threatens" to extinguish the Balearic lizard (Podarcis pityusensis).
The study, published in 'Ecology', states that these snakes "have not only devastated" the lizards on the main island, but, being able to swim across the sea, are also extinguishing populations with unique colorations on the nearby islets.
The study analyzes the evolution of the horseshoe whip snake invasion in Ibiza, a species that arrived on the island almost 20 years ago through the importation of olive trees and has now also been detected in Formentera.
The researchers, who have been conducting this work for six years in the Balearic Islands, point out that the Balearic lizard has suffered a "drastic reduction" in the last 20 years and could disappear entirely from the island.
To carry out the study, in the case of the islet of Santa Eulària, 12 traps were installed and up to 58 snake specimens were captured between 2023 and 2025; they also compared lizards observed in the same transects – a virtual fixed strip used for research – with a census from 2016: While 72 lizards were recorded that year, in 2023 only three were detected and in 2025 no specimens were observed.
Thus, they have confirmed the extinction of this lizard's populations on a dozen islets, including Santa Eulària and s'Ora. Being small islets, this extinction happens very quickly because, as they explain, just a few snakes can wipe out the entire population in a matter of months.