The animal that’s everywhere and nowhere

A veterinarian holds a salamander called an axolotl inside a fish tank at the ecological restoration laboratory at Mexico City’s Universidad Nacional Autónoma de México in April 2021. While scientists estimate there are roughly 1 million axolotls in captivity, they’re almost extinct in the wild. | Luis Antonio Rojas for Vox

Axolotls are among the most widespread amphibians on Earth. In the wild, they’re almost extinct.

The small salamander known as the axolotl, whose cartoonish face resembles a smiling emoji, is among the most widespread amphibians on Earth. You can buy them as pets online, collect them in the game Minecraft, and watch them perform on Instagram and TikTok. Often pink in color with feathery external gills, axolotls are also popular in laboratories: Scientists love studying them because they can regrow limbs, spinal cords, and even portions of their brains. Roughly 1 million are under human care worldwide, according to some experts.

Yet in their home country of Mexico, where they’re celebrated as cultural icons, axolotls are critically endangered and on the verge of extinction. The only place you can find them in the wild is in a watery borough of Mexico City, the second-largest city in the Western Hemisphere. There are fewer than three dozen per square kilometer here, down from 6,000 in the 1990s.

This paradox — that axolotls seem to be everywhere and nowhere at the same time — raises a vexing question. If an animal is thriving in labs and aquariums, should we worry that it’s dying in its native waters? Or, asked another way: How important is the “wild” in wildlife?

Most searches for wild axolotls now end in failure, Luis Zambrano, a leading axolotl researcher at Universidad Nacional Autónoma de México (UNAM), told me last year. They’re simply too rare. Yet in November, I set out for Xochimilco (pronounced so-chee-MEEL-ko) in the south of Mexico City. I wanted to learn the lessons of axolotls in their natural habitat, and I had a hunch I might get lucky.

Some endangered animals live deep in the rainforest, far from civilization. Not the axolotl. The salamander resides in narrow canals that surround farms called chinampas, or “floating gardens,” and provide water for the crops and a way to travel. With its skinny streets and wooden boats ferrying people around, Xochimilco feels a bit like Venice, but with the added smell of freshly cooked tamales and the crow of roosters.

A farmer moves his wooden boat through a canal in Xochimilco, a borough of Mexico City, in November 2021.

The Indigenous Mexica were among the peoples who built the chinampas hundreds of years ago, when they ruled what Europeans dubbed the Aztec Empire. At a time when the city was home to five large lakes, axolotls thrived in the canals and the Mexicas used them as a source of food and medicine. They also revered the salamanders as spiritual beings and living representations of the god Xolotl — the dog-headed twin of Quetzalcoatl, one of their most important deities. (One creation myth suggests Xolotl transformed himself into different plants and animals to avoid being sacrificed, and his final form before he was found and killed was an axolotl.)

The Spanish invasion and centuries of colonization eroded traditional farming and changed the city’s unique ecosystem. As Mexico City grew, the lakes started drying up, sewage and agricultural chemicals fouled the waters, and two kinds of introduced fish multiplied in the canals. Today, the majority of farmers use fertilizers and pesticides, and most water in Xochimilco can’t support many native species. The animals that survive have to compete with invasive fish, which also eat axolotls.

Wandering the narrow streets of Xochimilco one afternoon, I asked locals where to find the salamanders. I eventually got a lead: I might find them near the intersection of two major waterways to the north. I crossed a few canals filled with dark, fetid water before the directions led me to a dimly lit room. It housed a small owl, turtles, and several tanks of the iconic salamanders. So much for wild axolotls.

As a swarm of tourists gathered around, I thought about the gulf between ecosystems and the human idea of nature. Here we were in the axolotl’s native land, gawking at their features as though they were somehow exotic. It’s easy to forget that these creatures were ever wild and part of a large community when they now live behind glass. It’s easy to forget that Earth’s rarest species share the same web of life as humans.

I had more luck in my search when I visited a farm owned by Felipe Barrera Aguirre, a farmer and veterinarian who wears his thick, black hair in a bun. He told me that he was restoring a population of axolotls in a canal on his land. On a chilly morning, I climbed into a wooden boat bound for Barrera Aguirre’s farm with photographer Luis Antonio Rojas.

Farmers travel through the early morning mist on a canal in Xochimilco in November 2021.

A white heron rests by the edge of a canal in Xochimilco.

Mist blanketed the canal as our boat cut through the water and the sun rose through the haze. A large egret resting on the bank took flight as we cruised by.

Half an hour later we arrived at his farm, which was small but exquisite. He led us past tall sunflowers, bright-red cherry tomatoes, and dew-covered spider webs to a small canal filled with aquatic plants. Stay silent and watch, Barrera Aguirre told me.

Axolotls are unusual even when compared to their amphibian brethren. While many salamanders morph into terrestrial creatures when they reach adulthood — losing their gills, fins, and other aquatic features in exchange for a body better suited to land — axolotls usually don’t. Most live their whole lives underwater, as if they never grow up. Fortunately for admirers on land, they still often come up for air.

Waiting for rare wildlife to show up is a test of patience. But in the stillness, I noticed life all around me, from an iridescent beetle scaling a blade of grass to shrimp-like animals zipping through the water. This, I thought, is what biodiversity looks like — countless plants, animals, and microbes all doing their own thing in a complex network.

Felipe Barrera Aguirre, with his camera at the ready, waits for an axolotl to appear in a canal in his chinampa one early morning in November 2021.

A wild axolotl swims to the surface of a canal in Barrera Aguirre’s chinampa.

An hour or so in, just as I was giving up hope, a brown axolotl broke the surface. It drew a quick breath into its open mouth before retreating into the darkness. Then another appeared, about the size of a banana. For a split second, I stared at one of the rarest wild animals on Earth.

If axolotls are so rare in the wild, how did they become common everywhere else? The story begins in the 1860s, when a French expedition, tasked with exploring Mexico’s resources, brought 34 axolotls from Mexico City to a zoo in Paris, according to a history of axolotl research. Scientists and naturalists went on to breed those salamanders and distribute them around Europe, and by the 1870s they were found in all European countries — and eventually the US.

Remarkably, most axolotls under human care descended from that single group of fewer than three dozen (although over the years, scientists have bred a few wild axolotls and even tiger salamanders into the captive population). Wild axolotls are typically dark brown, whereas lab and pet animals are often white or pink. There are also genetic differences between the two groups, according to Randal Voss, an axolotl researcher at the University of Kentucky.

Courtesy of Hani Singer

An axolotl rests inside a piece of PVC pipe in a tank at Jessica Whited’s lab at Harvard University.

Not long after the French expedition, scientists made axolotls a staple of medical research. In fact, “axolotls were already mundane participants in laboratory life” when a scientist named Thomas Hunt Morgan first started studying the iconic fruit fly in the 1910s, according to the historical account. Early on, researchers used these salamanders to study the development of embryos and the hormone thyroxine. Now, they’re common in regeneration research.

More recently, axolotls found fame in Western popular culture. They’re sought-after pets with a massive social media following: the hashtag #axolotl has 1.8 billion views on TikTok. (I highly recommend this video, in which a drawing of a chef’s hat turns an axolotl into a tiny chef.) Axolotls also star in an ever-growing list of websites and games, including the hugely popular game Axie Infinity, in which users collect, breed, and battle cartoon axolotls. Some players have earned more in the game than in their traditional jobs.

Axolotls are no less iconic in Mexico, where they’re depicted in murals throughout Mexico City. The salamander is even the city’s official emoji and appears on the country’s new 50-peso note.

A mural of an axolotl in the Nativitas neighborhood of Xochimilco.

A man walks past a mural of an axolotl in the Caltongo neighborhood of Xochimilco.

But fame has done little to save them. The animal that most people know and love isn’t wild, but a captive creature, which doesn’t help them in Xochimilco. “Everybody says we have to save the axolotl, but they don’t care much about the ecosystems in which they live,” Zambrano said.

For 15 years now, Mexican scientists like Zambrano have been teaming up with farmers like Barrera Aguirre to rebuild populations of axolotls in their native waters. They aim to restore canals and revive traditional farming practices; for example, by planting a wider range of crops and spraying fewer chemicals. The ultimate goal is to release axolotls back into the wild where they can survive and breed.

On a hot November afternoon, I met Crescencio Hernández at his farm in a neighborhood of Xochimilco called San Gregorio. Not long ago, Hernández used chemical fertilizers and pesticides to grow his crops, which polluted the canals surrounding his farm. Then he started working with Carlos Uriel Sumano Arias, one of Zambrano’s colleagues. Sumano Arias helped Hernández use fewer chemicals, adopt natural fertilizers, and build a rudimentary filter that cleans the canal and prevents the unwanted fish from entering.

Carlos Uriel Sumano Arias checks the clarity of the water from a canal in Xochimilco in November 2021. He helps farmers in the area clean up their canals and build refuges for axolotls.

I made sure not to step on young stems of broccoli and kale as I walked along the canal. A green frog croaked and jumped into the water and, on the far bank, I saw a small water snake — hardly thicker than a string of yarn — slip into the grass.

Sumano Arias, a man in his 30s wearing a Panama hat, pulled up a few aquatic plants with roots that looked like glass noodles. “They smell good,” he said, lifting them to his nose and then passing them to me. That means the water is clean, he added. Sumano Arias plans to follow in Barrera Aguirre’s footsteps and introduce axolotls here in April.

Seedlings growing in a chinampa in Xochimilco.

A butterfly rests on a marigold in a chinampa in Xochimilco.

Sumano Arias checks the roots of aquatic plants from a canal bordering a chinampa.

A rudimentary filter keeps pollution, sediment, and unwanted fish out of a canal.

Axolotls don’t directly benefit farmers or ecosystems in some grand or obvious way. Rather, they’re an indicator species, almost like a canary in a coal mine. No axolotls probably means dirty water. And like other native animals, they’re part of a complex system. Their absence is like a broken cog in a finely tuned machine.

What’s bad for these salamanders is also bad for people, Zambrano added. Farmers in Xochimilco have a hard time selling produce because “the public believes these products are polluted,” he wrote in a recent paper. That’s pushed many of them to use more agrochemicals and prioritize quantity over quality, or to abandon their farms altogether. Those who take over the abandoned plots often dump sewage into the canals, he wrote, which makes the water even dirtier and feeds a vicious cycle of habitat loss.

The flip side is that restoring the ecosystems here — fixing many faulty cogs at once — also benefits farmers and those who buy their crops. An ecosystem that sustains axolotls can produce clean water for healthier, better-tasting produce, said Esperanza Hernández Flores, Crescencio’s sister, who also works on the farm.

“Water availability and quality are as important to axolotls as they are to local people who grow crops within Xochimilco,” Zambrano wrote in 2015.

Returning axolotls to the land is also a kind of cultural revival, Agustin Galacio Gonzalez, another farmer who participates in the UNAM program, told me. “It’s an important species for the heritage of the area.”

Luis Zambrano, an ecologist at UNAM who leads a project to create refuges for axolotls in Xochimilco, at his office in Mexico City in November 2021.

Zambrano aims to get at least 200 farmers to join the project, but that may be a challenge: Farmers told me that the market for natural products in Mexico is small and hard to access, and that eco-friendly methods tend to produce fewer crops. There are also other kinds of waste, such as sewage and pollution from new buildings, that dirty the canals, Zambrano acknowledged.

Nonetheless, Zambrano and his team have hope for Xochimilco’s axolotls. Just 15 years ago, relatively few people knew about these salamanders, he said, and now they’re showing up in the news and popular culture. That’s put Xochimilco on the map, he said. The urbanites of Mexico City are starting to realize that important species live in their own backyard, not just in distant protected areas, Zambrano added.

When helping animals also helps humans, these kinds of projects can work, he told me. When efforts to save species pit environmentalists against local communities, they fail. “You have to work with the people inside,” Zambrano said. “They have to own the project.”

Two axolotls that morphed into land-based salamanders in a fish tank at UNAM’s ecological restoration laboratory in November 2021.

Zambrano has an axolotl aquarium at his lab at UNAM. When I visited, I noticed two salamanders that were out of the water and seemed to be missing their external gills. Sometimes axolotls follow their amphibian cousins and transform into land-based creatures. It’s a response to stresses like changes in water quality, Voss, of the University of Kentucky, said. While salamanders may look fragile, they’re actually pretty resilient. Maybe they do stand a fighting chance.

Jessica Whited, a professor of regenerative biology at Harvard, has a thing for axolotls. Her office in Cambridge, Massachusetts, is decorated with axolotl paintings, and a cloth cape embroidered with an axolotl hangs in the corner. On a coffee table near the door, there’s a small jar filled with axolotl feet next to a glass container of Tootsie Pops.

Whited leads one of the largest axolotl labs in the country. She met me on a cold and rainy fall morning, talking rapidly about salamander science and often erupting into laughter. There were thousands of axolotls a few floors below us, she told me, in a room she calls “the baby factory.”

Courtesy of Hani Singer

Researcher Jessica Whited in the lab she leads at Harvard, where she studies limb regeneration in axolotls.

Whited is chasing what she calls a “holy grail”: the regeneration of human limbs. “People losing limbs in the United States due to disease is an ever-increasing problem,” she said. “There’s simply nothing that would be as perfect as coaxing the human limb to regenerate.” Her own grandfather underwent several amputations linked to peripheral artery disease before he passed away in his early 60s.

This work is possible because the anatomy of an axolotl is surprisingly similar to our own, Whited said, holding the jar of salamander feet to the light. “We are discovering how these animals actually regenerate limbs,” she said. “Then we can take this information and say which parts of this process are not happening in humans.”

Whited has no doubt that humans will eventually be able to regenerate their own limbs. “The question is just when,” she said. Now, her team is trying to identify what part of the axolotl genome — which, curiously, is about 10 times the size of the human genome — controls regeneration.

“The biggest discoveries are yet to come,” she said.

Courtesy of Hani Singer

An axolotl limb five days into regeneration.

Courtesy of Hani Singer

An axolotl limb 35 days into regeneration.

In Whited’s brightly lit lab, thousands of axolotls live in hundreds of containers on shelves. The young ones, which were around 2 inches long and wriggled in small plastic tubs, had partially transparent skin — I could see right through to their intestines, which looked like brains.

We were far from the wild axolotls that still live in the canals of Xochimilco. But I knew that these two worlds were deeply connected. Whited’s research — and so much of what we know about human and animal biology — wouldn’t have been possible without the wild animals that Mexican scientists and farmers are racing to save. What other secrets does the vast, wild world hold?

Cutting-edge medical research may one day give people a healthier life. But if Zambrano and Barrera Aguirre are right, so will reviving some of the traditional farming methods in Xochimilco. We need both the old and the new — the chinampas and the Harvard labs.

Felipe Barrera Aguirre takes an early morning walk through his chinampa in Xochimilco.

On Barrera Aguirre’s farm, every plant and animal served a purpose. Bees from his hives pollinate the crops, fennel attracts wasps that scare away insect pests, and axolotls keep the aquatic food chain in balance by feasting on smaller organisms, he told me.

Biodiversity wasn’t a concept for him — it was a way of life. “It’s very easy to understand the importance of biodiversity,” Barrera Aguirre said while stacking fresh-picked cherry tomatoes. “Each tomato is like a piece in a tower. When it becomes unstable, it falls.”

Luis Antonio Rojas contributed reporting to this article.