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A pair of researchers with Island Ecology and Evolution Research Group, Instituto de Productos Naturales y Agrobiología, has found that an invasive species of snake has killed off nearly all of the reptiles native to Gran Canaria. In their paper published in Proceedings of the Royal Society B, Julien Piquet and Marta López-Darias describe their comparison of habitats impacted by the importation of an invasive snake species and those that have not.

In 1998, California kingsnakes were imported onto the island of Gran Canaria; subsequently, some escaped or were released intentionally by pet owners. Since that time, the snakes have mated, reproduced and populated the island. In this new effort, the researchers sought to learn more about the impact of the snakes on the island's reptile population.

The California kingsnake is naturally found in western parts of the U.S. and Mexico. They are nonvenomous, come in a variety of colors and grow to 150 cm in length. They are diurnal generally, but have been found in some instances to behave nocturnally when temperatures are hot. Their diet consists of birds, rodents, amphibians and reptiles. The snake is considered to be harmless to humans, despite occasionally biting people, and have thus become a popular pet. And because they are so popular, they have been transported to other parts of the world.

In this new effort, the researchers noted that reptile populations on Gran Canaria—the third largest of the Canary Islands—have been in decline. To find out if it might be related to the invasion of the California kingsnake, they conducted a census of reptiles on Gran Canaria and other islands nearby that have not been invaded by the snakes. In so doing, they found major differences. They found, for example, that the population of giant lizards on Gran Canaria was 90 percent lower than nearby islands, skinks were 80 percent lower and geckos were 50 percent lower.

The findings show the scale of the impact an invasive species can have. The researchers note that their findings also highlight the need for stronger regulations regarding importing invasive species, most particularly in places with sensitive ecosystems such as those found on islands.