A recent study from the National Autonomous University of Mexico (UNAM) shows in 1998 there were 6,000 axolotls per square kilometer in Xochimilco. By 2008 that figure had plummeted to 100. And in 2014 researchers found less than one per square kilometer.

There are at least three major causes for its decline: urbanization, water pollution and the massive invasion of exotic predator fish like carp and tilapia, introduced by the Mexican government in the 1980s to help feed local communities. From the first few thousands they introduced, there are now an estimated 900 tons of fish in these canals.

“It’s an amazing amount. About 98 percent of the biomass in the water is made up of just these two fish, and they destroy everything,” said professor Luis Zambrano, an ecologist at UNAM who studies Mexican salamanders and the deterioration of their environment. “The government didn’t know what they were doing. They’ve altered the food chain and the whole ecosystem.”