Things aren’t going swimmingly for Telmatobius culeus. First, there’s its common name: the frog species is known as the Lake Titicaca scrotum frog because of its loose skin, which draws in the limited oxygen of the lake waters. The frogs, which can grow up to two pounds, are already listed as critically endangered by the IUCN, the international body that assesses threatened species. But Peru's wildlife ministry recently reported that over 10,000 of the frogs were found dead along a 30-mile stretch of the Coata River, from the Cacachi Bridge to its mouth at Juliaca on the shores of Lake Titicaca.

Pollution in the Lake Tititcaca basin, the frog's only home, and predation of its eggs by invasive trout have reduced their numbers by 80 percent over the last three generations, reports Dan Collyns at The Guardian. Because of its size—it’s the world’s largest water frog—poaching for food also takes a toll.

It's not known exactly what caused the mass die-off, but Max Blau at CNN reports authorities found sludge and solid waste flowing into the river, and many locals believe pollution from Juliaca was the cause of the deaths. Authorities have collected water samples from the river, which will be tested by Denver Zoo amphibian specialists Roberto Elias and Enrique Ramos.

Elias tells Collyns that his preliminary investigation showed that villagers recently began cleaning garbage out of the river, which may have stirred up contaminated sediment and could have impacted the frogs.

Whatever the case, it’s not an isolated incident. Pollution in Lake Titicaca is a growing problem.

Carlos Valdez at the Associated Press reports that industrial waste and heavy metals from cities has poisoned and killed off a large percentage of the lake's fish and amphibians. Farmers claim the water is so contaminated it stunts their crop growth. Runoff from mining operations in the mountains also contributes to the problem.

Peru and Bolivia, the two nations that straddle the 3,200-square-mile lake, have created a 30-person agency to monitor Titicaca. But it receives little funding to manage clean-up projects. Valdez says people are worried that the poor water quality will soon impact the tourist industry, which draws 750,000 visitors to the area every year.

Collyns reports that local environmental activist Maruja Inquilla Sucasaca took 100 dead frogs to the square in the city of Puno on the banks of the lake to bring attention to the problem. “No one took the pollution problem seriously until I showed them the dead frogs,” she says. “Lake Titicaca used to be a paradise, now we can’t use the water and our livestock die if they drink it.”

Stephanie Pappas at LiveScience reports that since 2010, the Denver Zoo has been breeding scrotum frogs confiscated from markets around the lake. The hope is to learn more about their biology and breeding behavior to better inform conservation plans and to keep a population of the frogs alive if the situation at Lake Titicaca worsens.