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Course:CONS200/2025FL1/Axolotl reintroduction & conservation in Xochimilco, Mexico City

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Introduction

June 2007 Tourism boating in Xochimilco
Images from Wikimedia Commons can be embedded easily.

Axolotls are a type of salamander that are native to the Mexican Central Valley. Despite captive individuals often bearing pink or light shades, in the wild, they are typically green or brown and sometimes contain silver highlights. Axolotls measure 22-45 cm in size and weigh anywhere from 60-230 grams. Unlike most amphibians, axolotls do not undergo metamorphosis and keep their juvenile features. They are a key indicator species of water quality, temperature, and pollution. Because of this, changes in their abundance often reflect deeper changes in water quality and overall ecosystem health. Axolotls have also held cultural significance in the region for centuries; they were associated with the Aztec god Xólotl and were historically considered an important species in local mythology and daily life[1].

Axolotls are near the brink of extinction, with only 50-1000 adults left in the wild[2]. From 2004 to 2008, the population declined 10-fold, from 1000 to 100, and compared to 1998, they saw a 60-fold reduction from 6000 individuals. They are currently on the IUCN Red List of critically endangered species[3].

Current Threats

The expansion of urban development in Mexico City led to habitat loss that has left the species critically endangered. Urban expansion in Mexico City has caused chemical runoff, water quality issues such as algae blooms, and the introduction of invasive freshwater species, which rely on the same food sources as axolotls. Urban expansion has such a drastic effect on axolotl because they occupy areas that are heavily populated [4]. Their current habitats are Lake Xochimilco, Lake Chalco, and the waterways of Mexico City, which are all subject to chemical and agricultural runoff due to increased industrialization, high population density, and the city's growing demands for water. Increased pollution of these habitats heavily affects the feeding and reproductive mechanisms of axolotls, leading to sharp population declines[5].

Conservation Mechanisms

Many conservation efforts are grassroots and field-based, focusing on habitat restoration. These efforts center around improving water quality and establishing refuges[6]. Starting in 2004, refuges have been created using artificial island plots, water filters, and careful monitoring and removal of invasive fish[7]. In addition, researchers are working on increasing the genetic diversity of wild axolotl populations in order to bolster the population size. Finally, axolotls have received a significant amount of recognition in media and the general public, leading to an uptick in funding for the research and conservation of the species[8]. There's currently a lack of significant and widespread government support, with urban developments continuing to pop up in and around these vital wetland areas[6].

Main Drivers of Species Loss

History and Vulnerability of Axolotl Populations

Axolotls are an endemic species of  Xochimilco, Mexico City, dependent on the unique wetland habitats that the area historically provides[4]. Their ideal habitat flourished during the Aztec empire, beginning in 1428, after an Alliance formed between the Tenochtitlan, Tetzoco, and Tlacopan city-states[4]. During this period of about 100 years, extensive canal systems were built with vast shoreline areas, a conducive habitat for these amphibious salamanders. Such habitats are comprised of cool, deep, and highly oxygenated fresh waters with a wide variety of aquatic plants and tree roots[4]. The vegetation and muddy environment at the bottom of the canals, referred to as floating farms, provide cover for Axolotls to find food, breed, and hide from predators, which are all adapted mechanisms for their survival[4]. With the deep canals built all over the area, Axolotls experienced low disturbances and had ample habitat to thrive, allowing migration and plenty of food to support the entire population. After the empire fell when it was invaded by Spain, there was a major spike in urbanization in major cities such as Mexico City, which led to the deterioration of the Axolotl habitat[4]. The delicate balance of the wetland ecosystem Axolotl population had become accustomed to drastically changed over a short period of time. Following this change in governance, the land systems in Xochimilco, Mexico City, were altered continuously until the present day, providing little time for these Salamander populations to adapt to their new conditions.

Habitat Degradation

The major developing city of Mexico required large supplies of water to support the growing population, industrial developments, and agricultural uses[9]. To fulfil the growing need for freshwater, much of the city's water supply came from draining the rivers and springs that supplied water to the canals, where Axolotls reside[9]. The once thriving wetlands became shallow basins with little water, reducing the vegetation and base ecosystem moss covers that Axolotls depend on for basic survival measures[9]. Because of the shallower depths, the temperatures of the waters slowly rose, and many of the original flora and fauna faced challenges adapting to changing conditions.

The lack of water available was not the only risk to the Axolotl population, reduced water quality also became a major threat to the vitality of their population. The fast-paced urbanization in Mexico City caused pressure on the fixed hydraulic regime in Xochimilco[9]. With the integration of developed cities, industrial agriculture practices were introduced to meet the needs of the growing population[9]. This change included the use of pesticides and fertilizers on plants at major agricultural developments. The runoff of chemicals eventually entered the canals of the Axolotl habitat and polluted the waterways, killing many invertebrates, like Axolotls[9]. The populations suffered an exponential decline as chemicals entered their freshwater habitat, food, and degraded the health of the surrounding ecosystem.

The introduction of new species into Axolotl's ecosystems is another main driver of their current species decline. Tilapia and Carp were introduced 20 years ago to improve food source availability for local residents, but also introduced survival issues for Axolotls[10]. The high reproduction rates of these two common fish and the lack of established fisheries caused their populations to grow exponentially, completely overpowering Axolotls in their shared habitat[10]. Axolotls and these fish have overlapping diets, drastically reducing the food availability for Axolotls and increasing mortality in their early stages of life[10]. Carp also consume Axolotl eggs in their diet, reducing the abundance in new generations of Axolotl[10]. Due to the lack of diversity in the axolotl's diet, feeding only on organisms such as fish, insect larvae, and oligochaetes, makes them especially vulnerable to ecosystem changes and restricted access to their rigid diets[10]. These habitats, once havens for Axolotl populations, are now not suitable for most Axolotls to live past their first year of life[11].

Urban Solutions and Their Impacts

Not only was there a reduction in water levels and changes to Axolotl's habitat conditions, but water extraction caused the land surrounding the canals to sink[4]. In order to combat the land sinking due to water extraction measures, the city approved the construction of a dam to maintain the water levels in certain areas[4]. Although the dam seemed to introduce a solution to land sinking and low water levels, this structure inhibits Axolotl’s movement patterns to escape predation and other risks. After a drastic decline in the biodiversity that is hosted by the canals, it was clear that the lack of fresh water supplied to the canals was becoming a threat to Xochimilco’s native species, specifically the axolotl[10]. To combat this issue, pipelines were built to replenish the depleted valleys with continuous water[4]. Although it was hoped to be a solution to Axolotl's species decline, it introduced greater issues of water quality. The water being sent through the pipes often fluctuated in quality, causing nutrient fluxes and algae blooms that damage the ecosystem's long term food web[10].

Current Remedial Actions

Captive breeding and Laboratory conditions

Inbred Axolotls in captive populations are very vulnerable to diseases, and wild Axolotls lack genetic diversity, resulting in their small population[12]. To address this, lab scientists continue with their research on the complex biology of the captive Axolotls, while other researchers breed and release Axolotls into controlled ponds and canals to hopefully restore some of their natural genetic diversity and to protect the wild population[12]. After releasing 10 captive-bred Axolotls into artificial ponds and 8 into natural ponds, researchers used trackers to monitor them in both environments[13]. After 40 days with constant monitoring all captive Axolotls were able to survive and gain weight, meaning they were able to hunt and scout good hiding spots in both environments[13]. With these results, researchers now plan to increase the numbers of artificial wetlands[13] .

For this method to work successfully, it requires the special management of water quality, housing strategies, food, and natural reproductivity to happen in laboratories, this also keeps Axolotls safe when they are still in captivity[14]. The housing of captive Axolotls requires them to be held in tanks containing more than 6 L of water, including the addition of natural or artificial plants to act as hiding spaces[14]. Water quality is maintained by the chemical, physical, and biological characteristics as measured by pH levels of nitrites, nitrates, and ammonia, this prevents the Axolotl from developing any skin and metabolic diseases[14]. Pelleted foods that contain high levels of protein are used in laboratory conditions, as live foods are difficult to obtain[14]. To have captive Axolotls successfully breed, timers are used to control the daylight hours, efficient filtering systems, programmable water chillers, and the chemical and physical monitoring of parameters are used, along with a much larger tank allowing 40 L of water per individual[14]. Small stones for spermatophores and artificial or natural plants to collect the embryos or oocytes for cryopreservations are placed, breeding tanks should also be prepared several days or weeks before collecting any biological samples[14].

Raising awareness

As the threat towards Axolotls grows, some conservation efforts are seen as controversial[8]. Although amphibians don't meet the criteria that flagships demand, the Axolotl was chosen as a flagship in Mexico as a conservation program[8]. This effort was aimed to promote nature based tourism by providing local boatmen with training in environmental interpretation[8]. The results after training showed that the boatmen's jobs satisfaction and incomes increased and that the environmental interpretation improved relevant knowledge and awareness of Axolotls in visitors[8]. This project was supported both regionally and internationally from zoos with captive Axolotls, providing publicity, funds, staff expertise, training support, and educational activities[8]. Dedicating the first and second day of February for the National Day of the Axolotls called El Día del Axolotl, offers workshops and activities focused on education and conservation[15]. Started in 2018 and has been going strong for five consecutive years, visitors participate in creating their own Axolotls with clay, watching documentaries such as Water Monster, and touring the Axolotl souvenir store and restaurants[15]. This raises awareness in children and adults regarding protecting and safeguarding this species[15].

Using entertainment and media presence, Axolotls have grown in popularity due to their adorable features[16]. From being able to adopt them online, to being seen in video games such as Minecraft, Axolotls are now among one of the most famous amphibians on Earth[16]. In their home country Mexico, the Axolotls are the official emoji in Mexico City, in Western popular culture, the Axolotl is a desired pet and receives billions of views on TikTok[16]. Even though fame has done little to help with the conservation of the Axolotls, their global popularity was able to create a campaign by the National Autonomous University called “Adopt an Axolotl”[17]. This campaign was created to raise money to create new artificial wetlands after the success of the released captive Axolotls in both natural and artificial wetlands, this campaign was able to raise nearly $30,000, able to maintain 40 artificial wetlands[17].

The Path Forward

Restoration projects following a “bottom-up” approach are being developed to revive local habitats within the Xochililco ecosystem. [6]These initiatives focus on recreating high-quality ecological niches that support the axolotl reproduction while protecting them from predatory fish. This strategy effectively aligns the values of the local economy with the long-term survival of the axolotl, as both the species and the surrounding communities depend on the availability and quality of clean water. Water quality is essential not only for irrigation and crop production, but also for maintaining a healthy lacustrine ecosystem. [6]To ensure these conditions, researchers plan to collaborate with farmers to establish local axolotl refuges equipped with semipermeable barriers positioned at the entrance of canals. These barriers reduce sediment flows and prevent the entry of invasive and predatory fish species, creating safer breeding environments. Such refuges also work to promote biodiversity by allowing non-predatory species, such as crayfish and silverside fish, to flourish. [6]Population analysis suggests that these restoration zones will counter the rate of previously predicted decline of axolotls in Xochimilco.

Government-led efforts have been difficult to implement, likely due to a limited understanding of urban wetland restoration and the need for consistency following long-term policies that prioritize ecological integrity and environmental stewardship. Counterproductive projects, such as high construction over the wetlands, threaten to increase water and air pollution and accelerate further urbanization, endangering the habitat. [6]The restoration of this ecosystem ultimately depends on policy shifts that prioritize environmental health, conservation ethics, and the protection of Xochimilco unique native species.

Darwin Initiative Project

An action plan for the conservation of the axolotl in Xochimilco was part of a 3-year UK Government Darwin Initiative Project, “Aztecs and Axolotls: Integrating Tourism and Conservation at Xochimilco, Mexico City”. Partners CIBAC (Centro de Investigaciones Biológicas y Acuícolas de Cuemanco) and DICE (The Durrell Institute of Conservation and Ecology), began the project in 2002 and held workshops in 2004 with representatives of the key government, NGO, and local stakeholder organizations as participants. [18]Activities during the workshops consisted of presentations and activities, such as identifying the key elements affecting surrounding axolotl ecosystems: one of the species was first identified and categorized into broad subject areas. The key subject areas that emerged were: the biology of the species; ecological interactions; environmental factors; use and exploitation; legislation; social factors; political factors; and education. [18] These elements were each sorted based on priority, planned future actions and timeline, and provided the framework for the Plan.

For example, one goal of guaranteeing a suitable habitat for the axolotl includes actions such as obtaining hydrological maps of canals that detail the main affluent and current flow, performing analyses to determine the water quality in the canal system and promoting its cleanup and control, regularly investigating and monitoring water quality, and regularly monitoring the quality of sediment.[18]

Priority areas include the scaling up of the refuge creation, addressing the water pollution and hydrology, engaging and supporting local agriculture and livelihoods, interaction across scales (local to landscape to policy), and mining and adaptive management.[18]

Implementation of Restored and Artificial Habitats

In Mexico, a study observed the difference between movement patterns, home range, and habitat use of axolotls due to a change in habitat conditions. VHF telemetry was used to capture how releasing captive-bred axolotls into either restored or artificial wetlands influences their behaviour and abundance.

Axolotls were released into either a restored chinampa wetland or an artificial pond. Although axolotls survived in both sites, those released into an artificial pond exhibited larger home ranges and travelled greater distances than those released into the restored chinampa. The artificial pond in La Cantera Oriente also revealed that females tend to travel significantly greater distances than males, with an average of 86.75 meters daily for females and 54.33 meters daily for males.[7] In contrast, daily distance decreased with age in Xochimilco, without significant sex differences. Additionally, this study contributed further understanding of axolotl ecology and provides new approaches to improved conservation outcomes. Many other projects, including Project Chinampa Refugio, work to restore artificial wetlands with the help of local farmers. Conservation International has joined this project by installing biofilters built from volcanic rocks and reedy plants, improving water quality, keeping out pollutants and invasive fish, and creating an environment for axolotls to breed and thrive safely.

These findings suggest that more implementation of artificial habitats can benefit the endangered axolotls and create stable habitats, releasing some of the pressures as climate change accelerates. Blending restored native wetlands and managed artificial habitats alongside ongoing habitat monitoring may improve the axolotl's long-term survival prospects and prevent further decline of the species' abundance.[7]

Conclusion

Axolotls are vital to the wetlands in and around Mexico City. They serve as an indicator species for the region and are important secondary consumers in their ecosystem. Axolotls maintain the balance of their environment by controlling the population of small organisms such as crustaceans, smaller fish, and insects. Urban expansion, a decline in water quality, and increasing competition for food sources have decimated populations, leaving the species critically endangered. Current conservation mechanisms focus on habitat restoration through improving water quality and creating refuges, as well as laboratory work focused on captive breeding and genetic testing. Their status as a flagship species has helped conservation efforts garner additional support; however continued research and work are needed in order to preserve this critically endangered species, specifically to expand and protect the limited and threatened habitats they still have.

Conservation efforts are promising, with both grassroots and research-based initiatives focused on preserving their habitats. Ground-up efforts are focused on the restoration of water quality in the wetlands occupied by axolotl. In addition, groups are working to create protected areas, which allow for safer breeding and protection from predation[6]. Furthermore, adoption as a flagship species, along with widespread public support, has been vital to raising awareness and funding for the species[8]. Researchers have discovered that artificial wetlands can successfully be implemented as supplemental habitats, and current work is underway to increase the genetic diversity of axolotl in an effort to increase their population size[19]. Most important of all is curtailing urban expansion in these sensitive areas. However, continued urban expansion and associated pollution remain significant barriers to long-term recovery[3], by restricting the over-development in and around Lake Xochimilco, Lake Chalco, and the waterways of Mexico City, wild populations can start to rebound. The conservation outlook for the axolotl ultimately depends on coordinated management of the Xochimilco wetland system, including hydrological planning, habitat protection, and regulation of land use. Effective collaboration between researchers, local communities, and government agencies is considered essential to stabilize existing populations and improve the species survivability in the wild[3].

References

  1. ↑ Malacinski, George (1 May 1978). "The Mexican Axolotl, Ambystoma mexicanum: Its Biology and Developmental Genetics, and Its Autonomous Cell-lethal Genes". American Zoologist. 18: 195–206 – via Silverchair.
  2. ↑ "Appendices I, II and III". IUCN. 7 February, 2025. Retrieved 11/02/2025. Check date values in: |access-date=, |date= (help)
  3. ↑ 3.0 3.1 3.2 Contreras, Victoria (December 1 2009). "Recent decline and potential distribution in the last remnant area of the microendemic Mexican axolotl". Biological Conservation. 142: 2881–2885 – via Science Direct. Check date values in: |date= (help)
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 Voss, Randal; Zambrano, Luis; Woodcock, Ryan. "A Tale of Two Axolotls".
  5. ↑ Chaparro-Herrera, Diego (October 21 2013). "Effect of water quality on the feeding ecology of axolotl Ambystoma mexicanum". Journal of Limnology. 72: 46. Check date values in: |date= (help)
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 [Randal]; [Ryan]; [Luis] (2015 Nov 1). "A Tale of Two Axolotls". PubMed Central. BioScience. 65: 12. doi:10.1093/biosci/biv153 – via PMC. Check |author-link= value (help); Check |author-link= value (help); Check |author-link2= value (help); Check |author-link2= value (help); Check |author-link3= value (help); Check |author-link3= value (help); Check date values in: |date= (help)CS1 maint: date and year (link)
  7. ↑ 7.0 7.1 7.2 Ramos, Alejandra (30 April 2025). "Movement ecology of captive-bred axolotls in restored and artificial wetlands: Conservation insights for amphibian reintroductions and translocations". PLOS ONE. 20 – via Public Library of Science.
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 Bride, I.G; Griffith, R.A; Meléndez-Herranda, A.; Mckay, J.E (04 November 2008). "Flying an amphibian flagship: conservation of the Axolotl Ambystoma mexicanum through nature tourism at Lake Xochimilco, Mexico". International Zoo Yearbook. Retrieved 2 November 2025. Check date values in: |date= (help)
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 Zambrano, Luis; Rivas, Miguel Igancio; Uriel-Sumano, Carlos; Rojas-Villaseñor, Ruben; Rubio, Maya; Mena, Horacio; Vázquez-Mendoza, Diana; Tovar-Garza, Armando. "Adapting Wetland Restoration Practices in Urban Areas: Perspectives from Xochimilco in Mexico City".
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 Zambrano, Luis; Valiente, Elsa; Vander Zaden, Jake. "Food web overlap among native axolotl (Ambystoma mexicanum) and two exotic fishes: carp (Cyprinus carpio) and tilapia (Oreochromis niloticus) in Xochimilco, Mexico City".
  11. ↑ Zambrano, L; Vega, E; Herrera M., L.G.; Prado, E; Reynoso, V.H. "A population matrix model and population viability analysis to predict the fate of endangered species in highly managed water systems".
  12. ↑ 12.0 12.1 Vance, Erik (15 Nov 2017). "Biology's beloved amphibian — the axolotl — is racing towards extinction". nature. Retrieved 7 Dec 2025.
  13. ↑ 13.0 13.1 13.2 Gibbs, Anna (12 June 2025). "Captive-breeding axolotls may help avoid their extinction". ScienceNewsExplore. Retrieved 7 Dec 2025.
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 Servín, Erika; Alcantar-Rodriguez, Alicia; Medrano, Alfredo (13 Aug 2025). "Experiences with the management and breeding of Mexican axolotl (Ambystoma mexicanum), for research and biobanking purposes, in a vivarium". Frontiers. Retrieved 7 Dec 2025.
  15. ↑ 15.0 15.1 15.2 ContentEngine LLC, a Florida limited liability company (2 Feb 2025). "National Day of the Axolotl". ProQuest. Retrieved 7 Dec 2025.
  16. ↑ 16.0 16.1 16.2 Jones, Benji (25 Jan 2022). "The animal that's everywhere and nowhere". Vox. Retrieved 7 Dec 2025.
  17. ↑ 17.0 17.1 Kim, Juliana (27 Nov 2023). "To save axolotls, a campaign in Mexico asks people to virtually adopt them". npr. Retrieved 7 Dec 2025.
  18. ↑ 18.0 18.1 18.2 18.3 Griffiths, Richard; Bride, Ian; Meléndez, Alejandro; Álvarez-Romero, Jorge; Olivera-Avila, Carlos; Steck-Cortés, Amanda; Servin, Erika; Pérez Gil Salcido, Ramón; Arroyo-Quiroz, Inés (2004). Bride, Ian (ed.). The conservation of the axolotl (Ambystoma mexicanum) in Xochimilco, Mexico City: a species/habitat action plan. ResearchGate: Darwin Initiative, Durrell Institute of Conservation and Ecology (DICE). pp. 2, 14. doi:10.13140/RG.2.1.3173.3208.
  19. ↑ Ramos, Alejandra G; Mena, Mena; Schneider, David; Zambrano, Luis (April 2025). "Movement ecology of captive-bred axolotls in restored and artificial wetlands: Conservation insights for amphibian reintroductions and translocations". Retrieved 2 November 2025.

[1]

This conservation resource was created by Course:CONS200.
  1. ↑ Vance, Eric (15 November 2017). "Biology's beloved amphibian — the axolotl — is racing towards extinction". nature. Retrieved 2 November 2025.
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