Inside The Race To Save Wild Axolotls

FLORA LICHTMAN: Hey, it’s Flora Lichtman, and you’re listening to Science Friday.

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

LUIS ZAMBRANO: When you try to collect them and you don’t find anything, [LAUGHS] then you hate them until you start to understand them and start to understand why it’s so important for Mexican culture. Ó

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

LUIS ZAMBRANO: Thank you very much.

ALEJANDRO MAEDA-OBREGÓN: Hi, Flora. Yeah, thank you for having us. And yeah, excited to talk about our project.

FLORA 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?

LUIS ZAMBRANO: 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.

FLORA LICHTMAN: OK. So 1,000 axolotls per kilometer squared to just 36 axolotls per kilometer squared in 10 years.

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

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

LUIS ZAMBRANO: OK, 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 dried 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 it could occupy. This is a very strange wetland because it has been managed for 1,500 years from Nahuatl people, which were part of the Xochimilco culture.

And the Aztec culture used to manage this system, creating square islands, which are called chinampas. These chinampas are still because we’re still using them as a production for food. In the edges of these islands, they created a maze of canals. And in these canals, there live the axolotl. 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. [LAUGHS]

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

FLORA LICHTMAN: And these are on the chinampas, on these islands?

LUIS ZAMBRANO: Yeah, these are on the chinampas. Instead of the chinampa, they create these football courts, and also, to create the 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.

FLORA LICHTMAN: Alejandro, how does eDNA fit into this project?

ALEJANDRO MAEDA-OBREGÓN: So environmental DNA is these genetic sources that we find in the environment because living organisms are constantly shedding DNA into the wild. For example, us mammals, we leave hair, 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 every item has a specific barcode. So the same applies to our genetic code.

So we have found that with eDNA, we can try to obtain information not just of one animal, but of a wider range of animals. And more importantly, in the case of axolotl, which are critically endangered, is a tool that we do not have to manipulate the animals directly. 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.

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

ALEJANDRO MAEDA-OBREGÓN: 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 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 the 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 found axolotls in some areas.

FLORA LICHTMAN: So the eDNA is telling you that these refuges that you’re creating are working.

ALEJANDRO MAEDA-OBREGÓN: 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 proof to say that this is working.

FLORA LICHTMAN: And what do the refuges look like? Yeah, just give me a sense of how they’re different, how the refuge is different from other parts of the lake.

ALEJANDRO MAEDA-OBREGÓN: 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 Xochimilco 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 build 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.

FLORA LICHTMAN: And the filter is filtering water that’s coming from the farm into the canal?

ALEJANDRO MAEDA-OBREGÓN: No, the filter water comes from the canals that have not filtered and arrived 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.

FLORA LICHTMAN: So you filter the water coming into this small canal.

ALEJANDRO MAEDA-OBREGÓN: Exactly.

FLORA LICHTMAN: OK.

ALEJANDRO MAEDA-OBREGÓN: 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 by far better in terms of the biodiversity. You will see phytoplankton, zooplankton. You will see crayfishes. So it’s very, very different. You can–

FLORA LICHTMAN: You can see it.

ALEJANDRO MAEDA-OBREGÓN: –take a picture within 10 meters distance. You will see huge differences.

FLORA LICHTMAN: Luis, is the solution here to just buy chinampas and make them all into refuges?

LUIS ZAMBRANO: Oh, no, no, no. [LAUGHS] No, no. I can tell you why this is not a good idea. The chinampas are owned by local people. And these local people have 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 the environment for axolotls, other species, buy a chinampa. But these are people that has resources. So it’s a sort of gentrification of Xochimilco. So we don’t want to do that. We want to help to collaborate with chinampas to get a better income for them.

FLORA LICHTMAN: Hmm. Last question, why have you committed your career to this animal, to conserving this animal?

ALEJANDRO MAEDA-OBREGÓN: Well, I want to work in something that people care about because as Luis was saying, axolotls and other species, just like our golden eagle in our flag, they are part of our cosmovision and 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, and while still preserving the resources for the future generations, for both its animals and its people.

FLORA LICHTMAN: Luis, what about you? Why axolotls?

LUIS ZAMBRANO: That is a very good question because I haven’t answered that very fast and easily. And I think I still don’t have an answer. Probably part of the reason is because axolotls are lovely. I mean, axolotls were like a love in the second date. It was not a first love. I mean, the first time I started to work with them, I hated them, let me tell you.

FLORA LICHTMAN: How could you hate an axolotl? It’s impossible.

LUIS ZAMBRANO: Yeah, when you try to collect them, and you don’t find anything, then you hate them until you start to understand them and started to understand why it’s so important for Mexican culture. Because it has been around Mexican culture for, again, 1,500 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 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 Cortázar, Octavio Paz, et cetera. So axolotls is not only important for pre-Columbian cultures. It has been highly important for Mexican culture.

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

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

FLORA LICHTMAN: That is an inspiring way to end. Thank you.

LUIS ZAMBRANO: Thank you.

ALEJANDRO MAEDA-OBREGÓN: Thank you very much, Flora.

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FLORA LICHTMAN: Dr. Luis Zambrano 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.

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