The Natural History and Captive Care of the Mexican Axolotl, Ambystoma mexicanum: Natural History – Part 1

 

Relatively scarce in the pet trade when I first began in the field (admittedly quite awhile ago!), interest in the Mexican axolotl has exploded in recent years, and today it is arguably the most commonly-kept salamander in the USA. Its popularity has soared in other countries as well, and oddly enough, it has become somewhat of a pop culture figure in Japan.

The Mexican axolotl has the rare distinction of being simultaneously one of the world’s most highly endangered amphibians (in the wild) and a common pet and laboratory subject.

Please note: the aquatic larvae of all species of salamanders are termed “axolotls” in some references, i.e. as in “tiger salamander axolotls”. The name as used here refers to young and adult Ambystoma mexicanum only.

Classification
Class: Amphibia
Order: Caudata
Family: Ambystomatidae

A complex of a dozen or more related aquatic salamanders dwell in mountainous lakes in the vicinity of this species’ range. The waters inhabited by one of these, the Lake Patzucuaro salamander (A. dumrelii), are high in dissolved salts. Perhaps as an adaptation to its brackish environment, this salamander sheds its outer skin layer continuously throughout its life.

The family Ambystomatidae, limited to North America, contains approximately 40 terrestrial and aquatic members, including such well known species as the tiger salamander (A. tigrinum), marbled salamander (A. opacum), spotted salamander (A. maculatum) and Pacific giant salamander (Dicamptodon ensatus).

Physical Description
The Mexican axolotl is stoutly built and reaches 9-12 inches in length. The head bears large, bushy red gills and the laterally compressed tail is equipped with a swimming fin. Wild specimens are dark brown in color; albino, leucistic, black and piebald strains are common in laboratories and the pet trade.

Range
This species’ entire natural range is limited to an area of 6.2 square miles in size. It is native only to Lakes Chalco and Xochimilco, adjacent to the southern edge of Mexico City, in central Mexico.

It appears now to survive only in a small fragment of that tiny habitat – the southern remnants of Lake Xochimilco, and perhaps within associated canals and private garden ponds.

Habitat
The Mexican axolotl is entirely aquatic. The high-altitude lakes it inhabits are deep, heavily-vegetated, mud-bottomed and cool in temperature. Axolotls can extract oxygen from air or water, utilizing gills, lungs and skin.

Status in the Wild
This salamander is extremely rare in the wild, and is considered to be among the world’s most endangered amphibians. Recent surveys in its tiny natural range have turned up only 0-42 specimens, despite 1,800 net casts.

Lake Chalco has been largely drained, and no axolotls survive there. Lake Xochimilco has been severely polluted and impacted by flood control measures, and is extensively channelized to accommodate “floating gardens” of flowers and vegetables.

Protected by the Mexican government and listed on Appendix 2 of CITES, Mexican axolotls are none-the-less still collected for the food and medicinal trade, and are also threatened by large populations of introduced fish (Tilapia and carp).

Click: The Natural History and Captive Care of the Mexican Axolotl: Part 2, To read the 2nd half of this article.