Captive-bred axolotls reintroduced into Mexico City canals survived, gained weight, and showed wild behaviors, offering hope for their conservation.
Captive-bred axolotls released into restored canals in southern Mexico City not only survived but also gained weight and displayed wild behaviors, offering fresh hope for the species’ conservation.
The Mexican axolotl (Ambystoma mexicanum) is famous for its perpetual grin and feather-like gills, yet its wild population has plunged to critically low numbers. Researchers estimate between 50 and 1,000 individuals remain in the wild, largely because urban growth and flood control turned the Valley of Mexico’s lakes into polluted canals. As a result, many axolotls now live only in captivity, where they can lose the skills needed to hunt, evade predators and reproduce.
In response, a team from the Autonomous University of Baja California, led by biologist Alejandra Ramos, tested whether captive-bred specimens could adapt to semi-natural waters. Between 2017 and 2018, they released 18 axolotls—nine females and nine males—into two locations: the historic canals of Xochimilco and the man-made La Cantera Oriente wetland, both south of Mexico City. These sites had undergone habitat restoration to mimic conditions that suit wild axolotls.
Over the next 40 days, the team attached small radio transmitters to each animal and enlisted volunteers to patrol the canals twice every day. To the researchers’ surprise, all 18 axolotls survived the trial period. When biologists recaptured several individuals, three showed notable weight gain. “If we can reintroduce these captive axolotls into a restored wetland where water conditions suit them, they can survive,” Ramos said.
Before the experiment, many feared the axolotls would lack essential survival skills. Captive breeding often fails to teach animals how to identify predators or catch live prey. However, the recovered specimens had gained weight—clear evidence they found and ate natural food and avoided predators. “They were hunting, eating, and avoiding threats. That was a big relief,” Ramos noted.
The study also uncovered unexpected behavioral patterns. Observers recorded that certain axolotls interacted more closely with specific peers, hinting at the ability to form social bonds. In addition, juveniles traveled farther distances than adult axolotls. Ramos suggested adults may better select resource-rich territories, reducing their need to wander: “Adults seem more efficient at choosing areas with food, so they don’t move as much.”
Despite these encouraging signs, risks remain. Researchers documented attacks by great egrets on some axolotls after the observation period ended. To help future releases, the team plans to introduce predator recognition training, teaching captive-bred axolotls to recognize and avoid common local predators before they enter the canals.
This project, published in PLOS One, marks one of the most encouraging developments in axolotl conservation. By proving that captive-bred axolotls can regain wild instincts, the study strengthens arguments for broader reintroduction efforts. Yet experts caution that long-term monitoring and continued habitat restoration are essential. Pollution, invasive species and habitat degradation still threaten the handful of wild axolotls that remain.
Ramos and her colleagues aim to scale up the program. They plan to involve local communities in habitat maintenance and water-quality monitoring. As more wetlands near Mexico City gain protection, conservationists hope to expand reintroduction sites. If these efforts succeed, they could help rebuild a self-sustaining wild population of axolotls in their ancestral home.
