An albino variety of California kingsnake popular in the pet trade has infested the Canary Islands, decimating native bird, mammal and lizard species that have had no time to evolve evasive patterns in what was once a stable ecology northwest of Africa.
Unchecked by natural predators, the kingsnake population has exploded, say U.S. Geological Survey biologists helping the Spanish archipelago attempt to control the highly adaptive and secretive predators.
"The kingsnakes in question are from a species found in San Diego and bred in captivity," said Robert Fisher, a research biologist with the USGS. "Some of their offspring wound up in the Canary Islands via the international pet trade, and then got loose.
"Now, their densities are going through the roof."
Fisher is among three U.S. experts heading to the Canary Islands in May to advise scientists and government officials on the behavior and potential vulnerabilities of the snakes that first raised alarms in 2007.
Since then, their populations have swelled to thousands per square mile in the eastern and northwestern portions of the 602-square-mile volcanic island of Gran Canaria — a kingsnake haven because of its mild temperatures, moist ocean air and lush terrain teeming with prey that never learned to fear snakes.
Dogs and hawks have been used in organized assaults against the snakes. So far, fewer than 2,000 have been snared, most of them discovered slithering over the ground.
"The trouble is, these snakes spend much of their lives beneath the ground," said Robert Reed, an invasive species specialist with the USGS. "So my message to people in the Canaries will be this: The fact that you're removing hundreds of visible snakes means, unfortunately, that it is likely that there are many, many thousands more out there you can't see."
Brian Hinds, president of the California chapter of the North American Field Herping Assn., will arrive in Gran Canaria with proposals for dealing with what he described as a "monumental task." Among them: plowing up infested areas with earth movers.
"They need to strike back hard and fast," said Hinds, who says he has personally captured more than 3,000 California kingsnakes. "They're not called kingsnakes for nothing."
The Canary Islands are another example of what can happen when an invasive snake gets a foothold in an otherwise balanced ecosystem. Brown tree snakes have established themselves as a breeding species in the Pacific island of Guam. The Florida Everglades have been invaded by Burmese pythons. The venomous wolf snake was introduced to the Indian Ocean island of Mauritius.
In the Canary Islands, albino and striped varieties of California kingsnake, known in scientific texts as Lampropeltis getula californiae, are roughly 30% larger than their wild counterparts in Southern California.
"They are a heck of a generalist predator, so they'll be eating any lizard they can fit in their mouths," Reed said.
Canary Island biologists fear that the snakesmay be nibbling three native species of gecko, skink and giant lizard into extinction.
"The data obtained show that the California kingsnake has a high ability to adapt and its spread to all of the islands is more than likely," said a 2012 study funded by the European Union and published by the International Union for Conservation of Nature. "This snake will quite possibly impact the local reptilian population to the point where we see their total disappearance."
Canary Island officials hope to eventually reduce their numbers by half, if possible.
"Most control programs for invasive reptiles are initiated long after the problem has gotten out of hand," Reed said. "Unfortunately, this sort of thing will probably become more common as international borders fall, incomes rise and more people get interested in owning exotic pets."