It's disturbing news for an admittedly ugly creature, which has a slimy tail, plumage-like gills and mouth that curls into an odd smile.

The axolotl is known as the "water monster" and the "Mexican walking fish." Its only natural habitat is the Xochimilco network of lakes and canals — the "floating gardens" of earth piled on reed mats that the Aztecs built to grow crops but are now suffering from pollution and urban sprawl.

Biologist Armando Tovar Garza of Mexico's National Autonomous University said Tuesday that the creature "is in serious risk of disappearing" from the wild.

Describing an effort last year by researchers in skiffs to try to net axolotls in the shallow, muddy waters of Xochimilco, Tovar Garza summed up the results as "four months of sampling — zero axolotls."