Invasive snake wipes out reptiles on Gran Canaria

Researchers have discovered that an invasive snake species is believed to have wiped out virtually all native reptiles on Gran Canaria.

The findings of Julien Piquet and Marta López-Darias, published in the journal Proceedings of the Royal Society B, include a comparison of ecosystems affected by the introduction of invasive snake species with those that were not.

Introduction of the California kingsnake to the island

California kingsnakes were introduced to Gran Canaria in 1998; some later escaped, while others were deliberately released by pet owners. Since then, the snakes have mated, bred and spread across the island, reports Phys.org.

To better understand the impact of the snakes on the island's reptile fauna, researchers launched a new study.

Despite its name, the California kingsnake is not native to either the United States or Mexico. Although not venomous, it can grow up to 150 cm long. They are usually not nocturnal, but have been spotted at night when it is particularly hot.

Among the animals they prey on are birds, rodents and amphibians. Despite their tendency to bite humans, the snake is generally considered a safe pet. And because they are so popular, they have spread around the globe.

Decline in reptile populations

Researchers on Gran Canaria, the third-largest of the Canary Islands, found that reptile populations had declined.

To determine whether this was linked to the invasion, researchers conducted a reptile count on Gran Canaria and on neighbouring islands not yet overrun by California kingsnakes. In doing so, they came across significant discrepancies.

They found that the number of large lizards, skinks and geckos on Gran Canaria was 90% lower than on the neighbouring islands.

The impact of an invasive species can be enormous, as these studies show. Invasive species should therefore be more strictly controlled, particularly in regions with sensitive ecosystems such as islands, the researchers say.

Efforts to eradicate the snakes

The snakes were found in houses, terraces and gardens. People who keep birds in their homes have discovered snakes in their cages, opening them and eating the birds.

This week's meeting of island specialists is part of a four-year strategy to halve the snake population. Restoration work began in 2011 and is expected to cost around €1 million.

One of the biggest obstacles is counting the snakes on the island, says Robert Reed, a USGS researcher visiting Gran Canaria this week. Since snakes spend most of their time underground, this means that even if hundreds of them are successfully caught, there are usually significantly more out there than one would like.

Californian Brian Hinds considers it unlikely that the animal can be eradicated on Gran Canaria. One must intervene quickly, otherwise the snakes will occupy 70% of the island, warns Hinds, who has been collecting and photographing king snakes in their natural environment for 35 years.