Ambystoma mexicanum

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AMPHIBIA	CAUDATA	AMBYSTOMATIDAE

Scientific Name:

Ambystoma mexicanum

Species Authority:

(Shaw, 1789)

Common Name/s:

English	–	Axolotl
Spanish	–	Ajolote

Taxonomic Notes:

The taxonomic validity of this species is confirmed, on the basis of morphology, allozymes, and mtDNA (H.B. Shaffer pers. comm.).

Assessment Information [top]

Red List Category & Criteria:

Critically Endangered B2ab(iii,v) ver 3.1

Year Assessed:

2006

Assessor/s

Luis Zambrano, Paola Mosig Reidl, Jeanne McKay, Richard Griffiths, Brad Shaffer, Oscar Flores-Villela, Gabriela Parra-Olea, David Wake

Evaluator/s:

Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)

Justification:
Listed as Critically Endangered because its Area of Occupancy is less than 10km2, its distribution is severely fragmented, and there is a continuing decline in the extent and quality of its habitat and in the number of mature individuals.

History:

2004	–	Vulnerable
1996	–	Vulnerable
1994	–	Rare (IUCN)
1990	–	Rare (IUCN 1990)
1988	–	Rare
1986	–	Rare (IUCN Conservation Monitoring Centre 1986)

Geographic Range [top]

Range Description:	This species is known only from central Mexico, on the southern edge of Mexico City, in canals and wetlands in the general vicinity of Xochimilco (including outside the Xochimilco city limits, around the Chalco wetland). The animals are not homogeneously distributed through their range, and congregate in particular places. Records from close to downtown Mexico City in the Chapultepec Lake could refer to either this species or Ambystoma velasci, and require confirmation. It was originally found in Lakes Xochimilco and Chalco (and presumably in the connecting lakes Texcoco and Zumpango), but it has disappeared from most of its range.
Countries:	Native: Mexico
Range Map:	(click map to view full version)

Population [top]

Population:	The surviving wild population is very small. Although populations are difficult to assess, recent surveys covering almost all of its known distribution range have usually captured fewer than 100 individuals (e.g., during 2002 and 2003, more than 1,800 net casts were made along Xochimilco canals covering 39,173m² and this resulted in a catch of only 42 specimens). A recent scientific survey revealed no Axolotls, although wild-caught animals are still found in the local market, which indicates that fishermen still know where to find them. There has not been a density study of the Chalco population, but evidence suggests that the population there is small and, furthermore, Chalco is a highly unstable system that runs the risk of disappearing in the near future.
Population Trend:	Decreasing

Population:

The surviving wild population is very small. Although populations are difficult to assess, recent surveys covering almost all of its known distribution range have usually captured fewer than 100 individuals (e.g., during 2002 and 2003, more than 1,800 net casts were made along Xochimilco canals covering 39,173m² and this resulted in a catch of only 42 specimens). A recent scientific survey revealed no Axolotls, although wild-caught animals are still found in the local market, which indicates that fishermen still know where to find them. There has not been a density study of the Chalco population, but evidence suggests that the population there is small and, furthermore, Chalco is a highly unstable system that runs the risk of disappearing in the near future.

Population Trend:

Decreasing

Habitat and Ecology [top]

Habitat and Ecology:	This species is native to the ancient system of water channels and lakes in Mexico City. It requires deep-water lakes (both natural and artificial canals) with abundant aquatic vegetation. Structures such as plants are needed to lay eggs. It is a paedomorphic species, living permanently in water, and does not undergo complete metamorphosis.
Systems:	Freshwater

Threats [top]

Major Threat(s):	The desiccation and pollution of the canal system and lakes in Xochimilco and Chalco, as a result of urbanization, as well as the traditional consumption of the species by local people, is threatening the survival of this species. It is also captured for medicinal purposes. The harvesting is targeted at animals that are less than one year old. It was formerly also captured for the international pet trade, although probably all animals in the international trade are now of captive origin. Introduced fishes (tilapia and carp) have increased to high abundances (a recent study collected 600kg of tilapia in one small channel using a 100m net) and have also impacted axolotls through competition and predation. The animals are also being affected by disease, probably spread by invasive species, and as a result of poor water quality. Although the water regime has changed in the last 10 years, and it is reported that pollution levels are decreasing, factors such as very high levels of bacterial contamination could still pose a serious threat.

Major Threat(s):

The desiccation and pollution of the canal system and lakes in Xochimilco and Chalco, as a result of urbanization, as well as the traditional consumption of the species by local people, is threatening the survival of this species. It is also captured for medicinal purposes. The harvesting is targeted at animals that are less than one year old. It was formerly also captured for the international pet trade, although probably all animals in the international trade are now of captive origin. Introduced fishes (tilapia and carp) have increased to high abundances (a recent study collected 600kg of tilapia in one small channel using a 100m net) and have also impacted axolotls through competition and predation. The animals are also being affected by disease, probably spread by invasive species, and as a result of poor water quality. Although the water regime has changed in the last 10 years, and it is reported that pollution levels are decreasing, factors such as very high levels of bacterial contamination could still pose a serious threat.

Conservation Actions [top]

Conservation Actions:	Conservation action is focusing on raising the profile of Lake Xochimilco through conservation education and a nature tourism initiative, coupled with work on habitat restoration and bioremediation. A species action plan has been drafted. There are several captive colonies around the world, since the species is used in physiological and biomedical research, as well as in the pet trade, but the re-introduction of captive-bred axolotls is not recommended until threats can be mitigated, and disease and genetic risks to the wild populations assessed. This species is protected under the category Pr (Special protection) by the Government of Mexico and is in process of being amended to a higher risk category. Although this species is currently on CITES Appendix II, it is currently under the process of "Periodic Review of species included in CITES Appendices".

Conservation Actions:

Conservation action is focusing on raising the profile of Lake Xochimilco through conservation education and a nature tourism initiative, coupled with work on habitat restoration and bioremediation. A species action plan has been drafted. There are several captive colonies around the world, since the species is used in physiological and biomedical research, as well as in the pet trade, but the re-introduction of captive-bred axolotls is not recommended until threats can be mitigated, and disease and genetic risks to the wild populations assessed. This species is protected under the category Pr (Special protection) by the Government of Mexico and is in process of being amended to a higher risk category. Although this species is currently on CITES Appendix II, it is currently under the process of "Periodic Review of species included in CITES Appendices".

Citation:	Luis Zambrano, Paola Mosig Reidl, Jeanne McKay, Richard Griffiths, Brad Shaffer, Oscar Flores-Villela, Gabriela Parra-Olea, David Wake 2006. Ambystoma mexicanum. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on 07 November 2009.
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