Axolotls are a type of amphibian – but with a difference. They have been described as the Peter Pan of amphibians because they never grow out of their aquatic phase. As a group of animals, the planet’s amphibians are in trouble. They are the most threatened group of vertebrates, and 41 percent of assessed species are listed as at risk of extinction on the International Union for Conservation of Nature (IUCN) Red List. Axolotls are only found in three isolated sites in the southern part of Mexico City and are very vulnerable to habitat loss. Most of what you read about these beleaguered creatures is bad news, but for once, we have a good news story to share with you! Thanks to a successful translocation program of captive-bred axolotls, these amazing creatures may have a chance to make a comeback.
About Axolotls
The axolotl habitat at Lake Xochimilco is being lost.
©Liz Pichardo/Shutterstock.com
Axolotls (Ambystoma mexicanum) are a paedomorphic salamander, which means that they retain their juvenile features and aquatic lifestyle into adulthood. They are an endemic species of Lake Xochimilco in Mexico, where they have been severely affected by habitat loss caused by urban expansion, environmental degradation, and a decline in water quality. The arrival of invasive species has only made things worse.
The situation became so bad that conservationists had to consider translocation to try to save them. This process involves moving a species from one area to another. It is often combined with a captive breeding program. This method is not without challenges. Not all animals breed well in captivity, and some do not adapt well to wild conditions. More importantly, if the root causes of population decline are not tackled at the same time, you are simply breeding animals to die in the wild.
Restoring and Creating Habitats
During the Aztec era, wetlands surrounding Lake Xochimilco in Mexico were partially transformed into canals surrounding rectangular islands called chinampas. Even though these were established to aid food production, they also supported local biodiversity. However, these habitats have been threatened and degraded over time.
In 2004, the Laboratorio de Restauración Ecológica at the Universidad Nacional Autónoma de México (UNAM), in collaboration with local chinampero farmers, initiated a project to create refuges within chinampas to support native species, including the axolotl.
Ongoing challenges and climate change mean that it is also necessary to create new habitats for species such as the axolotl, which are more likely to remain stable over time. One such area is the La Cantera Oriente (LCO) located in the protected area of the Reserva Ecológica del Pedregal de San Ángel (REPSA). This is an artificial wetland created as a byproduct of basalt mining activities, which brought underground springs to the surface. They have developed into thriving habitats that include potential prey species such as crayfish for adult axolotls and zooplankton for their larvae.
Studying Axolotl Translocation
Axolotls are the Peter Pans of amphibians.
©Iva Dimova/Shutterstock.com
The study was conducted at two sites: a restored chinampa in Lake Xochimilco and a pond in the artificial wetland of La Cantera Oriente (LCO). Previous pilot studies had confirmed that the areas were suitable habitats for axolotls.
A total of 18 captive-bred axolotls (nine females and nine males) were fitted with tiny transmitters so that their movements could be tracked. They were randomly released at the sites over a period of months. Using the transmitters, the researchers were able to monitor the axolotls’ home ranges, hourly travel distances, and daily travel distances. They also recaptured three axolotls to assess their health and condition. Would the released axolotls survive, and how would they behave in their new habitats?
Study Findings – Good News and Bad News
The main study finding was that the released captive-bred axolotls survived and successfully foraged in both habitats. The weight gained by the recaptured individuals demonstrated this. However, predation was still an issue, and the researchers witnessed great egrets attacking adult axolotls. Sadly, predation is the leading cause of translocation failure for many species. Captive-bred animals may not have the anti-predator behaviors that wild-born animals possess. Pre-release training to improve predator awareness could help address this issue.
Analysis of the axolotl movement data also revealed some interesting findings. Those released into the artificial wetlands had larger home ranges and traveled greater daily distances than those in the restored chinampas. The axolotls also seemed to have a narrow thermal preference range.
What Does This Research Mean for Axolotls?
These findings are good news for a species that is at risk of extinction. It has been shown that captive-bred axolotls can thrive and forage successfully after translocation to both protected natural and artificial wetlands. The ease with which they adapted to the artificial wetlands is especially exciting. These habitats provide more stable conditions where habitat degradation and climate change impacts can be mitigated. Finally, the study indicates that future programs should investigate the use of predator awareness training before release, together with ongoing habitat monitoring. Both strategies could improve the survival chances of released axolotls.
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