Spanish researchers have confirmed that horseshoe whip snakes are swimming from Ibiza to nearby islets, posing a new threat to the endemic Ibiza wall lizard. A video shot in April 2024 captured a snake swimming 450 metres from Ibiza's east coast to the islet of Santa Eulària, providing the first concrete evidence of this behaviour.
The horseshoe whip snake, a non-venomous species from mainland Spain, has colonised at least 90% of Ibiza since arriving two decades ago, likely via imported olive trees. The snakes have devastated the lizard population, which is now listed as endangered by the International Union for Conservation of Nature.
Biologist Oriol Lapiedra of the Centre for Ecological Research and Forestry Applications noted that the snakes on Ibiza are thriving, with some exceeding 2 metres in length and weighing 2.5 times more than mainland counterparts. Increased competition for food may be driving them to swim to islets.
Researchers observed a dramatic decline in lizards on Santa Eulària, from 72 in 2016 to just three in 2023. Unique lizard populations on ten islets have gone extinct. A captive breeding programme at Barcelona zoo aims to preserve the species, but the situation remains critical.
