Axolotl (Ambystoma mexicanum) Fact Sheet: Population & Conservation Status

Wild population estimates

• Populations extremely small (Contreras et al. 2009; IUCN SSC Amphibian Specialist Group 2020)
• Only 50–1,000 adults remaining (IUCN SSC Amphibian Specialist Group 2020)
  • But many thousands housed in research laboratories, zoos, or personal collections as pets (e.g., Recuero et al. 2010; Reiß et al. 2015; Vance 2017)

Population structure (in the wild)

• Overall, low genetic diversity (Recuero et al. 2010; Parra-Olea et al. 2012) — but genetically similar to other tiger salamanders living in Central Mexico (Everson et al. 2021)
  • Live in unconnected aquatic habitats
• Large ancestral populations buffered the species from some negative effects of inbreeding, genetic drift, and past genetic bottlenecks (Parra-Olea et al. 2012)
• Evidence of some regional population structuring (Recuero et al. 2010)

IUCN

• Critically Endangered (2019 assessment) (IUCN SSC Amphibian Specialist Group 2020)
  • Population trend: decreasing
• Previous assessments (IUCN SSC Amphibian Specialist Group 2020)
  • 2010: Critically Endangered
  • 2006: Critically Endangered
  • 2004: Vulnerable
  • 1996: Vulnerable

CITES

• Appendix II (UNEP 2022)

Government laws and regulations

• Protected as an endangered species by the Mexican government (Sciences et al. 2006; NOM-059-SEMARNAT 2010; SEMARNAT 2018; IUCN SSC Amphibian Specialist Group 2020)

Habitat designations

• Lake Xochimilco
  • Inscribed as a UNESCO World Heritage Site (Griffiths, Graue, et al. 2004; Zambrano et al. 2009)
  • Part of a protected wetland Ramsar site (Griffiths, Graue, et al. 2004; Bride et al. 2008; SEMARNAT 2018)

Habitat loss and degradation

• Drying out and pollution of canal systems (Zambrano 2006; IUCN SSC Amphibian Specialist Group 2020)
• Driven by urbanization and tourist activity
• Poor water quality (Schaffer 1989; Griffiths et al. 2003; Mazari-Hiriart et al. 2008; SEMARNAT 2018; IUCN SSC Amphibian Specialist Group 2020)
• High concentrations of bacteria, excessive nutrients, and heavy metals (Griffiths, Graue, et al. 2004; Zambrano et al. 2009)
• Sewage enters waterways after large storms (Zambrano et al. 2010a; Vance 2017)
• Lake Xochimilco fed with water from a single treatment plant (Voss et al. 2015)
• Continued urbanization in the Xochimilco district (Schaffer 1989; Adamson et al. 2022)

Introduced fish

• Tilapia and carp prey on and compete with axolotls, possibly over all life stages (egg, larvae, adult) (Zambrano 2006; Zambrano et al. 2007; de Jesus Chaparro-Herrera et al. 2011; Vance 2017; SEMARNAT 2018; IUCN SSC Amphibian Specialist Group 2020)
• Introduced by Mexican government in the 1970s and 1980s to reduce hunger and support new industry (Tapia and Zambrano 2003)
• Axolotl had no significant predators other than humans before the fish introductions

Trade

• Assumed all international trade today uses individuals reared in managed care (IUCN SSC Amphibian Specialist Group 2020)
• Former illegal local trade for human consumption, medicine, pets (IUCN SSC Amphibian Specialist Group 2020), and less commonly, for biomedical research (Sciences et al. 2006)
• Presumed to have ceased due to few remaining wild individuals
• Also see McKay (2003)

Habitat programs

• Conservation biologists and farmers (chinamperos) are working to improve water quality and exclude introduced fish in canals (Zambrano et al. 2009; Valiente et al. 2010; Zambrano et al. 2020)
  • Traditional agriculture practices encouraged (to not use fertilizers or pesticides) (Zambrano et al. 2015b, cited by Voss et al. 2015; Wanderer 2018)
  • Products certified as using axolotl-friendly practices if farmers use water from restored canals for irrigation and crop washing (Zambrano et al. 2015b, cited by Voss et al. 2015; Zambrano et al. 2020)
    • Certification program: Etiqueta Chinampera
• Artificial wetlands used to house and breed a small number of axolotls for reintroduction (Vance 2017; Ramos et al. 2021)
  • Offers ability to control water conditions, such as temperature, pH, and oxygen
• Larger pond area in Chalco region due to restoration efforts (Zambrano et al. 2006)

Reintroductions

• Creation of axolotl refuge areas, beginning in 2014 (Zambrano et al. 2020)
• Rewilding project at Lake Xochimilco (Cenisio 2022)
  • Reared at National Autonomous University of Mexico
    • Genetic stock from 1990s collecting
• Individuals released into Lake Chapultepec and appear to be breeding (IUCN SSC Amphibian Specialist Group 2020)
• Chalco system considered “unusable”; population may disappear in the near future (IUCN SSC Amphibian Specialist Group 2020)
  • Approximately 10,000 individuals released in 2012 to establish a stable population
• Also see Distribution

Awareness raising

• Ecotourism efforts to conserve Lake Xochimilco, along with habitat restoration (Griffiths, Graue, et al. 2004; Griffiths, Graue, et al. 2004; Bride et al. 2008; Griffiths et al. 2008; IUCN SSC Amphibian Specialist Group 2020)
  • Trained boat guides (remeros) interpret axolotl natural history during weekend tours (Bride et al. 2008)
• Training for artists in creating axolotl-themed souvenirs (Griffiths, Graue, et al. 2004; Griffiths et al. 2008)
• Education and art competitions at local schools (Griffiths, Bride, et al. 2004; Bride et al. 2008)
• Fundraising by scientific institutions
  • E.g., "Adopt an Axolotl" Campaign (National Autonomous University of Mexico Foundation)
    • Campaign website [in Spanish]

Axolotl conservation groups

• Laboratorio de Restauración Ecológica, Instituto de Biología (IB-UNAM)
• Centro de Investigaciones Biológicas y Acuícolas de Cuemanco (CIBAC)
• Centre for Biological and Aquaculture Research
• Axolotl breeding facility near Xochimilco
• GIA-X (The Axolotl Research Group-Xochimilco)
• Universidad Autónoma Metropolitana Unidad Xochimilco (UAM-X)
• Durrell Institute of Conservation and Ecology (University of Kent, UK)
• IUCN/SSC Amphibian Specialist Group

Xochimilco's waterways have been degraded by urbanization — but endure as important sites for recreation, tourism, and wildlife conservation.

On weekends, boat operators (remeros) punt visitors along lake canals in colorfully decorated traditional boats (trajineras).

Some remeros present stories about Mexican history and axolotl conservation in their tours. One study showed this approach improved people's appreciation of axolotls and boosted income for remeros.

Image credits: top: © rebeccanineill via Flickr. Some rights reserved./bottom: © Ronald Woan via Flickr. Some rights reserved.