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Wednesday
Jul082015

Unloved And In Danger: The Axolotl (ambystoma mexicanum)

The axolotl is described as the ‘Peter Pan’ of the amphibian world due to its retention of its larval features into adulthood, a phenomenon known as neoteny. It essentially remains in its juvenile form for its entire life cycle as it never undergoes metamorphosis. It is a naturally rare occurring species, being endemic to the eastern Peubla in central Mexico and is found in just one single lake – Laguna Alchichica. This location is perfect for axolotls, providing abundant vegetation known as ‘chinampas’ for both foraging and the attachment of their eggs. Axolotl is a Latin name that stands for water (‘atl) and monster (‘xolotl’) yet despite their odd appearance axolotls are very timid creatures and are the 8th most endangered species in the world.

flickr / francis mckeeCurrent Status

Current population estimates of the axolotl are murky with no accurate range currently unavailable. However what is known is that the wild population surviving in Mexico is very small, particularly in comparison to the numbers of axolotls currently bred in captivity. Recent estimates put the population at somewhere between 700-1200 individuals but conservationists believe a more realistic figure is <100 individuals currently left in the wild. Population abundance surveys have not yielded positive results:

•    in 2006, >18 00 sampling nets covering 39 173m2 recovered just 42 individuals,

•    from 1998-2004 the density of the axolotl population decreased from 0.006 individuals per m2 to just 0.001 individuals per m2,

•    this density reduction from roughly 6000 per km2 in 1998 to just 100 per km2 in 2008 represents a 6-fold decrease in the axolotl population in a single decade

In response to their shrinking population the axolotls were included on the IUCN Red List (2006), being listed as ‘Critically Endangered’.
flickr / mountainamoebaWhat are the Main Threats?

The justification for their inclusion on the IUCN Red List is numerous: first is their very small area of occupancy (i.e. their habitat range) which is less than 10km2. In fact the axolotl can only be found in just 6 isolated areas within one region of Mexico. This demonstrates the level of fragmentation of their habitat and is another key reason why there are listed as endangered. Human development (i.e. dams, farming land) cuts populations off from one another and prevents easy access to resources. Another key factor behind their endangered status is the deteriorating water quality of the canals they inhabit. Again this is caused by anthropogenic activities with the growing urbanisation of Mexican cities leading to increased pollution levels resulting from surface water run-off.

A new threat in the form of invasive species is adding to the pressure currently impacting the axolotl population. In particular the introduction of carp and tilapia fish species is a particular concern to the future of the population. These have been released into the Peubla region due to their importance in controlling aquatic weeds and insects. However both species out compete axolotls for resources and the tilapia fish will also consume axolotl eggs. The latter in particular has shown huge increases in abundance in recent years with one survey finding 600kg of tilapia fish within a single 100m net. Furthermore axolotls are also targeted by local fishermen both for their use in traditional dishes as well as for medicinal purposes.

What is being done?

The axolotl is recognised as a ‘Special Protection’ species by the Mexican government and is listed on the CITES II appendix which restricts trade in endangered species. Conservationists have begun building mini ‘shelters’ for the axolotls in Laguna Alchichica within areas of the highest quality to help them breed in clean waters. These shelters act as permeable cages that can help to protect the eggs from predation by invasive species. Work has also focused on community education and awareness by encouraging locals to take the axolotl off of their menu and explaining how they can get involved with restoration of the surrounding habitats. Whilst there is a large captive breeding project there are no plans to reintroduce axolotls into the wild due to the potential for outbreaks of the deadly fungal disease, chytrdiomicosis. Therefore the only way to stop the axolotl from becoming extinct is to focus on in situ conservation work within Mexico’s canals, the only place that axolotls call home.  

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