• Dominican nuns at a monastery in Mexico have become unlikely conservation heroes, maintaining the world’s largest captive population of critically endangered achoque salamanders, which number fewer than 150 in the wild.
• Scientists developed a microchipping technique to identify individual salamanders and found that the chips remained in place in 97.5% of animals for 175 days, with no negative health effects.
• The nuns’ 150-year tradition of breeding salamanders for the production of traditional cough syrup evolved into a critical conservation program after wild populations crashed in the 1980s due to lake pollution and overfishing.
• Lake Pátzcuaro, the salamanders’ only natural home, is shrinking and increasingly polluted due to sewage, fertilizer runoff, deforestation and climate change, making the captive breeding program and microchipping efforts essential for the species’ survival.

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In a monastery beside a 16th-century basilica in Pátzcuaro, Mexico, Dominican nuns move between rows of aquarium tanks, checking water quality and feeding earthworms to hundreds of brown salamanders with flowing gills.

Sister Ofelia Morales Francisco has cared for the critically endangered achoque salamander (Ambystoma dumerilii) for nearly 20 years. She and her team have mastered the amphibians’ complex reproductive biology, raising generation after generation in tanks that have become an unexpected ark.

This species, the achoque (pronounced ah-choke-eh), is known from only one lake on the planet, Lake Pátzcuaro in Mexico’s central Michoacán state. Scientists estimate that fewer than 150 adults remain in the wild. However, the monastery boasts a colony of around 300 salamanders, representing the largest known captive population in the world.

Scientists from Chester Zoo in the United Kingdom recognized that the monastery’s thriving colony offered an opportunity. They collaborated with Mexican conservationists to determine whether small, rice-sized identification chips could be implanted in captive achoques without harming the animals.

Dominican sisters at the Monastery of Our Lady of Health watch as researchers place microchips in critically endangered salamander. The nuns maintain the largest captive colony of this species of salamander. Photo courtesy of Chester Zoo, UK.

The microchips could enable conservationists to identify individual wild salamanders during catch-and-release health checks. With a quick scan, researchers can access information including sex, health status and approximate age for each animal.

According to their results, published in the Journal of Zoo and Aquarium Research, the microchips stayed in place in 97.5% of salamanders over more than 175 days, with no negative health effects.

“We were chipping them with the nuns watching protectively,” Adam Bland, assistant team manager for amphibians at Chester Zoo, said in a press release. “It’s a real demonstration of how anyone can be involved in conservation. People from all different backgrounds are working to save this species.”

A 150-year tradition becomes a lifeline

The Dominican sisters at the Monastery of Our Lady of Health have used achoques to produce a traditional cough syrup for generations, with some sources indicating the practice dates back 150 years. The syrup, believed to treat respiratory ailments such as coughs, asthma and anemia, became the convent’s main source of income, selling for about 200 pesos (approximately $10) per bottle.

When wild salamander populations crashed in the 1980s due to pollution and overfishing in the lake, the sisters realized both the species and their convent’s livelihood were at stake. In response, they began formalizing their conservation breeding program.

“The nuns have developed skills in a combination of working it out themselves as they have likely been breeding the species longer than other collections, and they have also had support from the University and Centro Regional de Investigaciones Pesqueras,” Bland told Mongabay.

“The best way to get them to copulate is by mating a male with three females,” Sister Ofelia Morales Francisco told AFP. “We have to raise the offspring very carefully, because they try to eat each other.”

Their breeding facility consists of two rooms filled with tanks housing hundreds of salamanders at a time. The nuns feed the salamanders organic earthworms and change water using a nearby well.

“This is probably the first time a religious community has been involved with amphibian conservation,” Gerardo Garcia of Chester Zoo told National Geographic. “They have a fresh environment, freshly harvested food, and they have a fully dedicated staff. It’s just what they need.”

Microchipping project brings high-tech hopes for critically endangered salamanders. Here, an achoque at Chester Zoo eats a worm. Photo courtesy of Chester Zoo.

Gentle handling for a lifetime ID

It is difficult to identify an individual achoque. They lack individual natural markings, and traditional marking methods like toe clipping fail because achoques regenerate lost tissues. Cut off a toe, and it simply grows back.

Because of their “weird biology,” Bland said, “amphibian species have been known to absorb microchips into their body and excrete them or push them back out through their permeable skin over time. Every species is unique, and marking techniques for amphibians often have to be species specific. It’s also crucial that the process doesn’t affect the animals’ health.”

The microchipping technique developed by the research team allows salamanders to be tagged quickly with minimal handling stress. The chip is implanted within a skinfold, where gravity keeps it in place after the animal returns to water. The entry site closes and heals without requiring tissue adhesive or aftercare, and salamanders showed no significant loss or behavioral changes in the months following chip implantation, according to the study.

The entire procedure takes minutes, but the new identifying marker should last for the salamander’s lifetime, said Bland.

Scientists place a small, rice-sized tracking chip beneath the salamader’s skin. This will allow scientists to identify individuals and to gather data during catch and release surveys in Lake Pátzcuaro. Photo courtesy of Chester Zoo

Scientists microchipped salamanders from four locations for the study: Chester Zoo in the U.K., the Regional Center for Fisheries Research, Michoacán University of San Nicolás de Hidalgo and 28 individuals from the monastery.

Conservationists now plan to catch and microchip the remaining wild achoques so their health and population numbers can be reliably monitored within Lake Pátzcuaro.

While microchipping advances identification, researchers in Mexico have also been “actively leading on surveying wild salamanders in order to understand the population,” Bland told Mongabay. “They are surveyed using nets in the lake, often in direct collaboration with local fisherman from the community. This work is already taking place.”

A lake in trouble

The salamanders’ only natural home, Lake Pátzcuaro, sits at 2,035 meters (6,675 feet) above sea level and is considered potentially one of the most studied and important lakes in Mexico, harboring several species found nowhere else on Earth.

The lake sits in an endorheic drainage basin, meaning water flows in but never flows out. So, what enters the lake stays in the lake.

“When pollutants flow into the lake, they stay there,” Paul Bamford, regional field program senior manager for Latin America at Chester Zoo, said in the press release.

The lake is also shrinking. It has “shrunk by 40km2 [15.4 mi2] and reduced its depth by 2.6m [8.5 ft] due to soil erosion in the habitat around the lake as a result of loss of the forested areas,” Bland told Mongabay in an email. “[W]ithout conservation action this will surely continue into the future.”

The study attributes salamander decline mainly to pollution from sewage, fertilizer runoff, soil erosion from deforestation and the shrinking lake.

“The water level is dropping because of climate change, so the contaminants are becoming more concentrated,” Bamford said.

Lake Pátzcuaro, photographed from the top of the Janitzio island in Michoacan, Mexico. Photo by Gengiskanhg via Wikimedia Commons CC BY-SA 3.0

“Amphibians are indicator species: they have permeable skin, so any toxins in the environment are likely to have a rapid negative impact on their wellbeing; their survival depends on good water quality,” Bamford said in the press release. “By monitoring and protecting achoque, we’re also protecting the lake.”

Overharvesting of salamanders, introduced predatory fish species, and parasites have also contributed to the decline, according to the study.

Despite some conservation efforts to clean up the lake and address predators, Lake Pátzcuaro remains polluted.

Looking ahead, researchers may release captive-bred salamanders into the wild to boost their numbers, if necessary, Bland said. However, they first need to finish studying the wild population to determine what conservation efforts are actually needed.

Mexican and U.K. conservationists are collaborating with communities to protect achoque eggs and continue breeding salamanders to ensure the species remains genetically diverse, according to Chester Zoo.

Meanwhile, the monastery remains a secure refuge for the achoques, and the sisters have no plans to curtail their care.

“If we don’t work to take care of it,” Sister Ofelia Morales Francisco said, “it will disappear from creation.”

Banner image of the critically endangered achoque salamander (Ambystoma dumerilii) eating an earthworm. Photo courtesy of Chester Zoo.

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Citation:

Bland, A., Garcia, G., Dominguez, O., Perez, R., & Preziosi, R. (2025). Evaluating retention of Subcutaneous Passive Integrated Transponder (PIT Tag) to individually identify captive Lake Pátzcuaro salamanders Ambystoma dumerilii.Journal of Zoo and Aquarium Research,13(3), 186-191. doi:https://doi.org/10.19227/jzar.v13i3.904