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An iconic salamander species, celebrated and studied around the world, is racing towards extinction.
When biologist Luis Zambrano began his career in the late 1990s, he pictured himself working miles from civilization, maybe discovering new species in some hidden corner of Mexicos Yucatán Peninsula. Instead, in 2003, he found himself counting amphibians in the polluted, murky canals of Mexico City's Xochimilco district. The job had its advantages: he was working minutes from his home and studying the axolotl (Ambystoma mexicanum), a national icon in Mexico and arguably the world's most recognizable salamander. But in that first year, Zambrano couldn't wait for it to be over.
"Let me tell you, I hated the project at the beginning," he says. For one thing, "I couldn't catch anything".
Over time, however, he did catch some axolotls. What he found surprised him - and changed the course of his career. In 1998, the first robust study to count axolotls estimated that there were about 6,000 of them per square kilometre in Xochimilco1. Zambrano - who now is a professor at the National Autonomous University of Mexico (UNAM) in Mexico City - discovered in 2000 that the number had dropped to about 1,000 animals per square kilometre. By 2008, it was down to 100; today, thanks to pollution and invasive predators, there are fewer than 35 animals per square kilometre1.
The axolotl is on the brink of annihilation in the canals of Mexico City, its only natural habitat. But although there might be just a few hundred individuals left in the wild, tens of thousands can be found in home aquariums and research laboratories around the world. They are bred so widely in captivity that certain restaurants in Japan even serve them up deep-fried.
"The axolotl is a complete conservation paradox," says Richard Griffiths, an ecologist at the University of Kent in Canterbury, UK, who recruited Zambrano to the project. "Because it's probably the most widely distributed amphibian around the world in pet shops and labs, and yet it's almost extinct in the wild."
This creates a problem for biologists. Thanks to its unique physiology and remarkable ability to regenerate severed limbs, the axolotl has become an important lab model for everything from tissue repair to development and cancer....