Science Friday - Inside The Race To Save Wild Axolotls

Episode Date: November 4, 2025

Axolotls are one of the most charismatic and beloved amphibians out there. But did you know that there’s only one place in the whole world where you can find them in the wild? It’s Lake Xochimilco in Mexico City.There, scientists are scrambling to save them from extinction by creating refuges, using environmental DNA to track them down, and tag-teaming with the farmers who work on the lake. Luis Zambrano, one of the world’s leading axolotl experts, and Alejandro Maeda-Obregón, a molecular biologist, talk with Host Flora Lichtman about their work to protect these beloved amphibians.Guests:
Dr. Luis Zambrano is a leading expert on axolotls and an ecologist at the National Autonomous University of Mexico.Dr. Alejandro Maeda-Obregón is a molecular ecologist at University College London who studies rare and endangered species.Transcripts for each episode are available within 1-3 days at sciencefriday.com.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hey, it's Flora Lickman, and you're listening to Science Friday. Today in the podcast, a quest to save one of the world's most beloved amphibians. When you try to collect them and you don't find anything, then you hate them until you start to understand them and start to understand why it's so important for Mexican culture. They're one of the most charismatic amphibians out there. They're crawling all over your social media with those little black guys and that goofy smile. and that poofy red gill scarf.

I know the sci-fri crowd knows what I'm talking about. The axoloddle. What you probably didn't know is that the only place in the world you can find them in the wild is in Lake Sochi-Milko. But their numbers are dwindling, and scientists are working on many fronts to protect them, from collaborations with farmers to creating refuges, to capturing environmental DNA or e-DNA to try to track them down.

Here to tell us about this mission to protect the axolotls are my guests. Dr. Luis Sambrano is one of the world's leading axolotel experts and an ecologist at the National Autonomous University of Mexico. And Dr. Alejandro Maeda Obregone, a molecular ecologist at the University College London, who is studying rare and endangered species. I want to welcome you both to Science Friday. Thank you very much. Hi, Florida. Yeah, thank you for having us. And yeah, excited to talk about our project.

Luis, let's start with you. If axolotls are only living in this one lake, I mean, how big is the wild population at this point? Well, it used to be very large. Actually, when I started to study them, we calculated that there were about 1,000 axolotles per kilometer square. That was in 2004. And 10 years ago, the last census we made officially was 36 per kilometer square.

So in the wild, there are very, very small amount of number of organisms. Okay, so 1,000 axolotls per kilometer squared to just 36 axolotls per kilometer squared in 10 years. Exactly. So the reduction is huge. And it obviously concerns us a lot because this is the only places where the white population exists. The axolotles are around the world in many times. But the only place that they can survive in the wild is this area called such a lot. Mexico. Tell us about this lake. What does it look like? How big is it? And why are axolotl's only living

there? Okay. Well, the lake is in the south part of Mexico City. The lake used to be huge. I mean, it was a five-late system. The other four, actually, they are completely dry out at this moment because the city is above that. So the axolotol used to have a larger population and have a larger range of area that he could occupy. This is a very strange webland because it has been managed for 1,500 years from Nahuatl people, which were part of the socio-chemical culture and the aspect culture, just to manage this system creating square islands, which are called Chinampas. These Chinambas are still because we're still using them as a production

for food. In the edges of the of this islands, they created a maze of canals, and in these canals, they just, they leave the axolotles. So the axolotles have a very, very strange, well-managed system by the human until about 100 years ago when we decided to destroy everything in this valley. And one of the things that we are reducing really, really bad is the habitat of the Absolutely. I mean, many people change the land use, and instead of creating food, they are using it for football courts, so for soccer courts. And there were a lot of football courts at this moment. And also... And these are on the Chinampas on these islands? Yeah. These are on the Chinampas. Instead of the Chinampas, they create this football courts. And also to create a spa and retreat and party areas in which they can last for three days with a lot of loud music. So this is another one. way of urbanization that we don't like because they create a lot of noise and a lot of garbage. Alejandro, how does eDNA fit into this project?

Environmental DNA is these genetic sources that we find in the environment because living organisms are constantly shedding DNA into the world, right? For example, us mammals, right? We live here, skin cells, right? saliva, right? Our own, like, you know, droppings. We have known for quite a while now that in our genetic data,

there are some segments that can be used as barcodes. Just imagine going to your favorite supermarket and, you know, every item has a specific barcode. So the same applies to our genetic code, right? So we have found that with DNA, we can try to obtain information not just of one animal, but of a wider range of animals, right? And more importantly, in the case of Axolot, which are critically endangered,

is a tool that we do not have to manipulate the animals directly, right? Therefore, we don't need to stress them that much. So it's becoming another tool that we can use to deliver important information to the people making decisions. Okay, so basically you go around collecting water samples, And then you see what DNA is floating in there. What did you learn? So, yeah, we are running a project that is trying to restore this system.

So we have created about 40 different refuge. And the only place that Alejandro found, the DNA of Axolotons were within these refuges. And we are doing at this moment, again, a third set of samples. And in the last one, not only we found axelotons within, the refuge, but also in two spots that we know that we normally find at solotol. So the axolotals outside of the refuge is still there. There are very, very few, but we still find Akrodotas in some areas. So the EDNA is telling you that these refuges that you're creating are working.

Yeah, that is a very good news. I mean, the good news is that the refugees are working very, very well. we now with the EDNA have the proof to say that this is working. And what do the refuges sort of look like? Yeah, just give me a sense of sort of how they're different, how the refuge is different from other parts of the lake. Well, first of all, yeah, we have, I mean, the canals are by far smaller. Canals in which the tourists, the people that goes to So Chameco to visit,

and the large canals are about 30, 40 meters wide, for example. And these canals are 1, 2 meters wide. So they are by far smaller. After we built the filter with the local farmers, funny fact about that is that the farmer decides how the filter is created. And I mean, we can create some very nice, very important type of filters, but they have to be maintained by the local farmers.

So once the filter is built, you will see really, really fast that the water quality increases because the transparency is larger. I mean, you can see the bottom of the lake within the refuge and outside of the refuge. You won't see that, for example. And the filter is filtering water that's coming from the farm into the canal? No, the filter water comes from the canals that have not filtered and arrive to the canal that has, I mean, it's the same water from inside than the outside. The only difference is that we filtered with plants.

So you filter the water coming into this small canals. Exactly. Okay. And the water is by far more transparent. The water quality, I mean, we measure phosphorus, nitrogen, heavy metals, etc. And it's by far reduced. You will see a lot of submerged plants also. I mean, it's well by far better in terms of the biodiversity.

you will see phytoplankton, zooplankton, you will see cryfishes. So it's very, very different. You can take a picture within 10 meters distance. You will see huge differences. Luis, you know, is the solution here to just sort of buy Chinampas and make them all into refuges? Oh, no, no, no. I can tell you why this is not a good idea.

The Chinapas are owned by local people. And these local people has been there for 1,500 years. So if we buy a Chinampa, it's also, I mean, because I've seen that lately a lot, a lot of people that has resources to buy Chinampas, to try to create an environment for Axelope with other species, buy a Chinampah, but these people that has resources. So it's a sort of gentrification of such a milton. So we don't want to do that.

We want to help to collaborate with Chinamperos to get a better income for them. Last question. Why have you committed your career to this animal, to conserving this animal? Well, I want to work in something that people care about because as we were saying, Axolotos and other species used like our golden eagle, right, in our flag. They are part of our cosmobition, many cultures in the country. And I think it's amazing to be, part of something that is going to improve the standards of people living in their home ecosystems, right, and while still preserving the resources for the future generations, right, for both its animals and its people.

Luis, what about you? Why axelotles? That is a very good question because I have an answer that very fast and easily. And I think I still don't have an answer. probably part of the reason is because axolotles are lovely this i mean axolotles were like a love in the second date was not at first like love i mean the first time i started to work with them i hate them let me how could you hate an axolotl it's impossible yeah when you try to collect them and you don't find anything you hate them until you

started to understand them and started to understand why is so important for Mexican culture. Because it has been around Mexican culture for, again, 15 hundred years. So, for example, they are considered the twin god of the most important god of Aztecs. So the twin ugly god of the most important god was the Axel. So, I mean, you see a lot of draws. And actually, Diego Rivera has a very important draw of Axel. The most important writers wrote about axolotles in Latin America, such as Julio Cortasar, Octavio, Paz, et cetera.

So axolotles is not only important for pre-Colombian cultures, it has been highly important for Mexican culture. Luis Alejandro, thank you so much for joining me today. Thank you very much. And if we save the axoloccal and we save out Sochi Milko, which is threatened by a city of 20 million people, we can save anything around the world. gives a lot of hopes. That is an inspiring way to end. Thank you.

Thank you. Thank you very much, Florida. Dr. Luis Sambrano is an ecologist at the National Autonomous University of Mexico. And Dr. Alejandro Maeda Obregone is a molecular ecologist at University College London. Thanks for listening. Don't forget to rate and review us. If you like the show. And you can always leave us a comment on this segment on Spotify. We'd love to hear from you.

Today's episode was produced by Rasha Airedi. I'm Flora Lichtenen. Thanks for listening.