Are Axolotls Endangered? Wild Axolotls of Xochimilco

What is the axolotl’s conservation status?

The axolotl (Ambystoma mexicanum) has been classed as Critically Endangered by the IUCN since 2006, and the latest assessment, published in 2020, confirmed that status with a decreasing population. It is also listed on Appendix II of CITES, the international treaty that regulates trade in wildlife, and is protected under Mexican law.

The main reason for the listing is its tiny, fragmented range. The axolotl is found naturally only in the Valley of Mexico, and today almost all wild axolotls live in one wetland: the canals and small lakes of Xochimilco, at the southern edge of Mexico City.

How fast has the wild population fallen?

Researchers have surveyed Xochimilco with nets over several decades. Their results show a dramatic decline:

In 2013 a search lasting several months at first found no axolotls at all, before a few were spotted in a network of side canals. Estimates of the remaining wild adult population range from roughly 50 to 1,000. Exact numbers are hard to get because the animals live in murky water and are now very scarce.

Why are axolotls endangered?

Several threats act together:

• Loss of the lakes. The Valley of Mexico once held a chain of large lakes. Draining began in Aztec and colonial times and continued through the 20th century to control floods and supply water. Lake Chalco and most of the other lakes are gone, and Mexico City now covers much of the old lake beds.
• Urban growth. Xochimilco itself is under pressure from new housing and roads that fill in canals, reduce water flow and bring in more waste.
• Water pollution. The canals are topped up with partly treated wastewater, and fertilizers and pesticides wash in from surrounding farms. The result is cloudy, oxygen-poor water. Farm chemicals have been shown to kill many axolotl embryos and larvae and cause abnormalities in survivors.
• Introduced fish. Common carp and tilapia were stocked to support local fishing. These fish eat axolotl eggs and young, compete for the same small prey and stir up the bottom where axolotls lay their eggs. Axolotls also become less active when these fish are around, which leaves them less time to feed and court.
• Small, inbred populations. With so few animals left in isolated patches, genetic diversity is falling, which can weaken the survivors over time.

What is being done to save wild axolotls?

The most promising work is based on the chinampas, the narrow farm islands built between Xochimilco’s canals since Aztec times. Scientists from the National Autonomous University of Mexico (UNAM) work with local farmers to turn some chinampa canals into refuges. Simple filters clean the water, and barriers keep carp and tilapia out, so axolotls can live and breed in safer conditions.

In return, the farmers grow vegetables with fewer chemicals and can sell them as axolotl-friendly produce. This approach protects the animal and also keeps a traditional farming system alive. Similar projects restore water quality, plant native water plants and teach visitors about the species.

Captive breeding plays a supporting role. Groups of axolotls descended from wild Xochimilco animals are kept by Mexican universities, zoos and community ajolotarios (axolotl breeding centers). Trials releasing captive-bred axolotls into protected canals and ponds have shown that they can survive, feed and grow, although some are eaten by herons and egrets.

Aren’t there millions of axolotls in captivity?

Yes, and that is one reason people are surprised the species is endangered. Axolotls have been bred in laboratories since 1863–1864, when a few dozen were shipped from Mexico to Paris. Their descendants now live in research labs, aquariums and homes around the world.

However, these captive axolotls are not a safety net for the wild population. They come from a small founding group, have been bred for generations in tanks, and some carry genes from tiger salamanders that were crossed into lab stocks. Releasing them could introduce disease or unsuitable genes. Saving the species means saving the wild animals and the canals they need.

How does the axolotl compare with other threatened salamanders?

Amphibians are the most threatened group of vertebrates, with about two in five species at risk of extinction, and salamanders are among the hardest hit. Other Mexican mole salamanders, such as the Lake Pátzcuaro salamander, face similar problems from pollution and introduced fish. Elsewhere, the Chinese giant salamander has been devastated by over-collection, and the hellbender of the eastern United States has declined because of dams and silt. Some of the causes are covered in why are amphibians declining?.

Unlike many amphibians, the axolotl appears to resist the chytrid fungus, a disease that has wiped out frogs worldwide. Its problems are almost entirely about habitat, pollution and introduced fish, which means they can still be fixed if the canals are protected.