Axolotl Facts: The Salamander That Never Grows Up

What is an axolotl?

An axolotl is a salamander, which makes it an amphibian, not a fish. Its most striking feature is that it is paedomorphic, or neotenic: adults keep larval traits such as feathery external gills and a finned tail into the reproductive stage of life ^[1]. Axolotls live their entire lives in the water ^[2].

So where does "never grows up" come from? In the wild, axolotls rarely if ever metamorphose into a land-living form. Metamorphosis can be induced in a lab with thyroid hormone injections, but most lab animals die shortly after it ^[1]. A 2022 review also reports that thyroxine-induced metamorphosis reduced regeneration rates by twofold ^[3]. The animal is not stuck as a baby; it simply reaches adulthood without leaving the water.

Color varies. Lab animals range from a dark, mottled brownish-green, called the wild type, to albino ^[1].

How big is an axolotl, and what does it look like?

Animal Diversity Web gives an average length of about 23 cm (9 in), says some axolotls exceed 30 cm (12 in), and lists a mass of 60 to 110 g ^[1]. A 2022 review gives 20 to 35 cm (8 to 14 in) from head to tail ^[3]. The sources differ slightly at the top end, so we use "about 20 to 30 cm" and treat 30 cm as a common size, not a hard limit.

The easiest feature to spot is the gills: three feathery projections on each side of the head ^[2]. The body is long and the tail is finned. Males have an enlarged cloaca, the opening used for waste and reproduction, while females have a smaller one and a rounder, plumper body ^[1].

Fact	Value
Scientific name	Ambystoma mexicanum
Group	Amphibian (salamander)
Length	About 20-30 cm (8-12 in)
Weight	About 60-110 g (2-4 oz)
Native range	Lake Xochimilco, near Mexico City
Conservation status	Critically Endangered
Lifespan in human care	About 5-15 years

Want to see the size against other animals? Try our size comparison tool or the animal vs animal tool.

Where do axolotls live, and are they endangered?

Axolotls are native only to the Valley of Mexico. They were historically found in Lakes Chalco and Xochimilco. Lake Chalco is gone, and Xochimilco remains only as scattered canals and swamps, at an elevation of about 2,274 m (7,460 ft) ^[1]. Because they live in fresh water, we file them under rivers and lakes.

The species is listed as Critically Endangered on the IUCN Red List ^[5] and in Appendix II of CITES, the international wildlife trade agreement. Habitat loss and the introduction of large predatory fish are the main threats ^[1]. A research review describes the animal as near extinction in its native Mexico, even though many axolotls live in labs ^[3].

Most axolotls people meet are therefore captive, and the animals in labs and homes are not a sign that the wild species is safe. Read more about how we think about this on our conservation page.

What can an axolotl regenerate?

Regeneration is the reason axolotls are famous in science. The National Institute of General Medical Sciences says the axolotl can regenerate almost any body part, naming the brain, heart, jaws, limbs, lungs, ovaries, spinal cord, skin and tail ^[2]. A 2022 review lists regenerating tissues including the retina, skeletal muscle, gills and teeth as well ^[3]. One exception noted there: lens regeneration works only within the first 2 weeks of life.

Scientists study this in the hope of learning how humans might better heal wounds or regrow damaged tissue ^[2]. The same article reports the axolotl genome is 32 billion base pairs, about 10 times larger than the human genome. A big genome does not by itself explain regeneration, and the researchers are still working out what does.

How long do axolotls live?

Lifespan depends on whether you mean the wild or human care, and we keep them apart. In human care, Animal Diversity Web reports an average lab lifespan of 5 to 6 years, with some individuals reportedly living 10 to 15 years ^[1]. For wild axolotls we found no reliable lifespan figure in the sources we could use, so we do not give one.

The life cycle starts with eggs. Wild breeding occurs generally from March to June, once a year. A female lays 100 to 300 eggs, one at a time, attached to rocks or plants, and the eggs hatch in 10 to 14 days. Axolotls reach sexual maturity at about one year, and the parents give no care after the eggs are laid ^[1].

What do axolotls eat?

Axolotls are carnivores. In the wild they take whatever small animals they can catch, from worms and insects to snails and small fish ^[1]. Pets and lab animals eat what their keepers provide. We cover prey types, life stages, feeding schedules and the wild versus pet differences on our full guide to what axolotls eat.

Can you keep an axolotl as a pet?

Many people do, and research labs have kept them since at least 1863. They need cool water. The University of Kentucky Ambystoma Genetic Stock Center keeps axolotls at 15 to 18 C (60 to 65 F) and says they should never be kept above about 22 C (72 F) ^[4]. It houses adults individually in bowls or two adults to a ten-gallon (38 L) aquarium as a rule of thumb.

Those are one research lab's practices, not a complete care guide. Axolotls need specific water quality, food and handling, so talk to a veterinarian with amphibian or exotic animal experience before bringing one home, and check the rules where you live. Never release a pet axolotl into local waters.