Critically endangered axolotls that were captive-bred then released into wetlands in Mexico City have successfully adapted to the wild, a new study has found, giving new hope to scientists trying to save the species from extinction.
Axolotls (Ambystoma mexicanum), found only in Lake Xochimilco, are one of the world’s most adored — and threatened — salamanders. Between 2017 and 2018, a team of researchers released then tracked 18 captive-bred axolotls in the ancient lake south of Mexico City, and in a nearby artificial wetland, to see how they would fare in the wild.
“The amazing news is that they all survived,” study lead author Alejandra Ramos, a biologist at the Autonomous University of Baja California, told BBC News. “And not only that, but the ones that we recaptured had gained weight — so they’re hunting.”
Axolotls retain juvenile features into adulthood, a rare trait called neoteny, which contributes to their reputation as “incredibly cute” with their wide eyes, feathery gills and smile-shaped mouth.
They can also regrow limbs and organs, garnering interest in the medical world, particularly in antiaging animal experimentation and cancer research. “If an axolotl loses an arm or leg, it grows back within two months, and it functions as before. The same with its eyes or brain,” biologist Vania Mendoza, the 2024-2025 Axolotl Census coordinator, previously told Mongabay contributor Boris Van Der Spek.
Fascination with axolotls has led to a boom in captivity, with most individuals of the species today being kept in homes and labs. Meanwhile, axolotl populations in the wild are estimated to have dropped by more than 80% in less than two decades. The species has been classed as critically endangered on the IUCN Red List since 2006.
Axolotl numbers fell by 99% between 1998 and 2014 in Lake Xochimilco due to environmental degradation and a severe decline in water quality largely driven by sewage and chemical pollution from agriculture.
But efforts to recover the historic lake’s chinampas, a human-made canal ecosystem of raised beds first built by the Aztecs that have historically served as refuges for axolotls, has given the salamanders another chance. Researchers released 10 individuals, five male and five female, into a 500–square-meter (5,380-square-foot) restored chinampa refuge equipped with filters to improve water quality and exclude exotic fish. In the artificial pond, they released four pairs.
In both wetlands, the axolotls could successfully hunt and forage. In Lake Xochimilco, though, two individuals were eaten by great egrets (Ardea alba), a common wetland bird. The study’s authors write that training future batches of axolotls in predator awareness before release could improve survival results.
Study co-author Luis Zambrano, a biologist at the Autonomous National University of Mexico, said that if the axolotl’s population and habitat can be restored in a city of more than 20 million people, “I feel that we have hope for humanity.”
Banner image: A purple axolotl (Ambystoma mexicanum). Image by Raphael Brasileiro via Pexels.
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