Inside The Race To Save Wild Axolotls

Lake Xochimilco in Mexico City is the only place where axolotls live in the wild, and they face growing threats.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Flora Lichtman?

  Hey, it's Flora Lichtman and you're listening to Science Friday.

• 0:07Flora Lichtman?

  Today in the podcast, a quest to save one of the world's most beloved amphibians.

• 0:13Speaker 01

  When you try to collect them and you don't find anything,

• 0:17Speaker 01

  you hate them until you start to understand them and start to understand why it's so important for Mexican culture.

• 0:27Flora Lichtman?

  They're one of the most charismatic amphibians out there. They're crawling all over your social media with those little black eyes and that goofy smile and that poofy red gill scarf. I know the sci-fi crowd knows what I'm talking about, the axolotl. What you probably didn't know is that the only place in the world you can find them in the wild is in Lake Xochimilco. 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 eDNA, to try to track them down. Here to tell us about this mission to protect the axolotls are my guests.

• 1:08Flora Lichtman?

  Dr. Luis Sembrano is one of the world's leading axolotl experts and an ecologist at the National Autonomous University of Mexico. And Dr. Alejandro Maeda Obregon, a molecular ecologist at the University College London, who is studying rare and endangered species. I want to welcome you both to Science Friday.

• 1:27Speaker 01

  Thank you very much. Hi Flora, yeah, thank you for having us and yeah, excited to talk about our project.

• 1:34Flora Lichtman?

  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?

• 1:42Speaker 01

  Well, it used to be very large, actually. When I started to study them, we calculated that there were about 1,000 axolotls per kilometer squared. That was in 2004. And 10 years ago, the last census we made officially was 36 per kilometer squared. So in the wild, there are very, very... Small amount of number of organisms.

• 2:07Flora Lichtman?

  Okay, so 1,000 axolotls per kilometer squared to just 36 axolotls per kilometer squared in 10 years.

• 2:16Speaker 01

  Exactly. So the reduction is huge. And it obviously concerns us a lot because this is the only places where the white population exists. Axolotls are around the world in many times, but the only place that they can survive in the wild is this area called Suchimil.

• 2:32Flora Lichtman?

  Tell us about this lake. What does it look like? How big is it? And why are axolotls only living there?

• 2:40Speaker 01

  Okay, well, the lake is in the south part of Mexico City. The lake used to be huge. I mean, it was a five lake system. The other four, actually, they are completely dry out at this moment because the city is above that. So the axolotl used to have a larger population and have a larger range of area that he could occupy. This is a very strange way plan because it has been managed for 1,500 years from Nahuatl people, which were part of the Suchimil culture and the Aztec culture, just to manage this system, creating square islands, which are called chinampas.

• 3:22Speaker 01

  These chinampas are still, because we're still using them as a production for food. In the edges of the of these islands, they created a maze of canals. And in these canals, they just they live the axolotls. So the axolotls 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 axolotl. I mean, many people changed the land use and instead of creating food, they are using it for football courts, so for soccer courts.

• 4:06Speaker 01

  And there are a lot of football courts at this moment.

• 4:08Flora Lichtman?

  And these are on the chinampas on these islands?

• 4:11Speaker 01

  Yeah, these are on the chinampas. Instead of the chinampa, they create these football courts. And also to create spa and retreat and party areas in which they can last for three days with a lot of loud music. So this is another way of urbanization that we don't like because they create a lot of noise and a lot of garbage.

• 4:31Flora Lichtman?

  Alejandro, how does eDNA fit into this project?

• 4:35Speaker 02

  Environmental DNA is these genetic sources that we find in the environment because living organisms are constantly shedding DNA into the wild, right? For example, us mammals, right? We live here, skin cells, saliva, our own 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 eDNA,

• 5:18Speaker 02

  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 axolotls, 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.

• 5:49Flora Lichtman?

  Okay, so basically you go around collecting water samples and then you see what DNA is floating in there. What did you learn?

• 5:56Speaker 02

  So yeah, we are running a project that is trying to restore the system. So we have created about 40 different refuges. And the only place that Alejandro found at the eDNA of axolotls were within these refuges. And we are doing at this moment again a third set of samplings. And in the last one, not only we found axolotls within the refuge, but also in two spots that we know that we normally find axolotls. So the axolotls outside of the refuge is still there. There are very, very few, but we still find axolotls in some areas.

• 6:39Flora Lichtman?

  So the eDNA is telling you that these refuges that you're creating are working?

• 6:45Speaker 02

  Yeah, that is a very good news. I mean, the good news is that the refuges are working very, very well. We now with the eDNA have the

• 6:53Speaker 01

  They prove to say that this is working.

• 6:56Flora Lichtman?

  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.

• 7:06Speaker 01

  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 Suchemiko to visit, and the large canals are about thirty, forty meters wide, for example. And these canals are one, two 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 there, I mean, we can create some very nice, very important type of filters, but they have to be maintained by the local farmers. Uh, so once the filter is built,

• 7:51Speaker 01

  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.

• 8:04Flora Lichtman?

  And the filter is filtering water that's coming from the farm into the canal?

• 8:09Speaker 01

  No, the filtered water comes from the canals that have not filtered and arrives to the canal that has. I mean, it's the same water from inside than the outside. The only difference is that we filtered it with plants.

• 8:22Flora Lichtman?

  So you filter the water coming into the small canal?

• 8:25Speaker 01

  Exactly.

• 8:26Flora Lichtman?

  Okay.

• 8:27Speaker 01

  And the water is by far more transparent. The water quality, I mean, we measure phosphorus, nitrogen, heavy metals, et cetera, 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 ten meters distance, you will see huge differences.

• 8:55Flora Lichtman?

  Luis, you know, is the solution here to just sort of buy chinampas and, and make them all into refuges?

• 9:02Speaker 01

  Oh, no, no, no.

• 9:05Speaker 01

  I can tell you why this is not a good idea. The chinampas are owned by local people. And these local people has been there for 1500 years. So if we buy a chimp, 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 axolotls, other species, uh, buy a chimp. But these people that has resources. So it's a sort of gentrification of such a meal. So we don't want to do that. We want to help to collaborate with Chinamperos to, to get a better income for them.

• 9:43Flora Lichtman?

  Hmm. Last question. Why have you committed your career to this animal, to conserving this animal?

• 9:51Speaker 02

  Uh, well, uh, I want to work in something that, that people care about. Because as we were saying, axolotls and other species use like a, a, a word, our golden eagle, right, in our flag. They are part of our cosmo vision and many cultures in the country. And I think it's, it's amazing to be part of something that, uh, is going to improve, uh, the standards of, of people living in their home ecosystems, right? And, and while still preserving the resources for, for the future generations, right? For both its animals and its people.

• 10:29Flora Lichtman?

  Luis, what about you? Why axolotls?

• 10:31Speaker 01

  Uh, that is a very good question because if I have an answer that is fast and easily. And I, I think I still don't have an answer. Probably part of the reason is because axolotls are lovely. This, I mean,

• 10:47Speaker 01

  axolotls were like a love in the second date. It was not a first sight love. I mean, the first time I started to work with them, I hate them. Let me.

• 10:58Flora Lichtman?

  How could you hate an axolotl? It's impossible.

• 11:01Speaker 01

  No, yeah, when you try to collect them and you don't find anything.

• 11:06Speaker 01

  I think you hate them until you start to understand them and start to understand why it's so important for Mexican culture. Because cats been around Mexican culture for, again, 1500 years. 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 axolotl. So I mean, you see a lot of draws and actually Diego Rivera has a very important draw of axolotl. The most important writers wrote about axolotls in Latin America such as Julio Cortazar, Octavio Paz, et cetera.

• 11:46Speaker 01

  So axolotls is not only important for pre-Columbian cultures, it has been highly important for Mexican culture.

• 11:54Flora Lichtman?

  Luis Alejandro, thank you so much for joining me today.

• 11:57Speaker 01

  Thank you very much. And if we save the axolotl and we save Oaxaca, which is threatened by a city of 20 million people, we can save anything around the world. Gives a lot of hopes.

• 12:08Flora Lichtman?

  That is an inspiring way to end. Thank you.

• 12:11Speaker 01

  Thank you.

• 12:12Speaker 02

  Thank you very much, Flora.

• 12:14Flora Lichtman?

  Dr. Luis Sembrano is an ecologist at the National Autonomous University of Mexico. And Dr. Alejandro Maeda Obregón 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 Aridi. I'm Flora Lichtman. Thanks for listening.