A New Threat to the Galapagos Tortoise: Mosquito Bites

By Eliza Strickland | June 2, 2009 10:11 am

Galapagos tortoiseThe mighty tortoises that roam the Galapagos Islands may not have many predators, but a new study suggests that the giant reptiles could run into serious problems due to the diminutive black salt marsh mosquito. Researchers genetically analyzed the mosquito, and found that it was not introduced recently by humans but instead arrived about 200,000 years ago. Since then the insect has evolved so much it is practically a distinct species from the mainland variety. For one thing, the insect has adapted to be able to feast on the blood of lizards, tortoises and other reptiles and not solely on mammals, as it does on the mainland [The New York Times].

That diversity of diet is what has researchers worried. If the black salt marsh mosquito picks up a disease like avian malaria or West Nile fever, it could quickly spread the disease to the Galapagos’s rare tortoises and marine iguanas. Says study coauthor Andrew Cunningham: “With tourism growing so rapidly the chance of a disease-carrying mosquito hitching a ride from the mainland on a plane is also increasing, since the number of flights grows in line with visitor numbers…. If a new disease arrives via this route, the fear is that Galapagos’ own mosquitoes would pick it up and spread it throughout the archipelago” [Telegraph].

When the mosquitoes first arrived on the islands about 200,000 years ago, the only mammal making its home on the island was the sea lion, says study coauthor Arnaud Bataille. “It [the mosquito] was looking for some blood. What it was going to find is these huge reptiles and marine iguanas, so I think it gave it a go and liked it a lot,” he said [BBC News]. The study, which will be published in the Proceedings of the National Academy of Sciences, also found that the mosquito has adapted to living and breeding not just in coastal swamps, but in inland areas at higher altitudes, increasing the chance that the insect could spread diseases across the islands.

Researchers say protective measures should be taken now, before outbreaks are detected. In an effort to cut the risk of mosquitoes and other insects being transported to the islands, the Ecuadorian government now require planes flying to the Galapagos to be sprayed with insecticide [BBC News]. But similar rules have not yet been introduced for the tourist ships that are making more frequent stops at the islands.

Related Content:
80beats: On the Galapagos Islands, an Evolutionary Puzzle That Darwin Missed
80beats: Lonesome George, the World’s Rarest Tortoise, Isn’t Ready to Be a Dad
80beats: Careful Crossbreeding Could Resurrect Extinct Galapagos Tortoise

Image: flickr / sly06

  • torres

    I thought mosquitos originally fed on reptile blood, then, as mammals became more prevalent, started feeding on them. Is there any data that suggests mosquitos stopped feeding on reptiles? Is feeding on reptiles just a latent ability of mosquitos? Couldn’t they do that anywhere, not just in the Galapagos?

  • Jenita

    Spraying passenger planes with insecticides? Someone’s getting rich off that deal and it’s the chemical companies which are jeopardizing the health of travelers.


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