A small success is being hailed as a big step forward for conservation efforts to protect the world's largest aquatic frog, the critically endangered Lake Titicaca frog (Telmatobius culeus). For the first time, frogs in captivity in their native country of Peru have laid fertile eggs, and although the resulting tadpoles did not survive, scientists trying to save the species have now overcome a "major obstacle," says Tom Weaver, area supervisor at the Denver Zoo, which is assisting with the project.
The frogs had only spawned in captivity previously at the Bronx Zoo in the 1970s, where the few tadpoles produced also died. That zoo's adult specimens died out in the 1990s.
Biologically unique, the Lake Titicaca frog is covered by loose folds of skin that allow it to breathe indefinitely underwater by absorbing oxygen from the water. Found only in the vicinity of South America's largest lake, straddling the Peru–Bolivia border, the species has seen its population drop precipitously since it was first brought to the world's attention by a Jacques Cousteau documentary in 1971. The frog, which at full size weighs nearly a kilogram and measures more than 50 centimeters, was listed as critically endangered by the International Union for Conservation of Nature and Natural Resources in 2004 after scientists observed an estimated 80 percent drop in frog counts over its last three generations.
Like most endangered species, threats to the Lake Titicaca frog include habitat loss and pollution. But the worst threat has been overharvesting of the frog for so-called medicinal purposes to "cure" all manner of diseases and enhance male virility. Unlike traditional Chinese medicine, "this is relatively new to their culture," Weaver says. "There was a doctor in the 1950s who was recommending that frogs were good for treating TB." Now frogs are consumed, usually after being turned dropped into a blender and turned into what the locals call "frog soup."
The Denver Zoo got started with conservation efforts in Peru a few years ago and has since made the species its top conservation priority. One of the first things they did was conduct interviews to find out why people were consuming the frog. "Everybody does it for a different medical reason," says Weaver. Although the zoo doesn't want to go in as Americans and tell the Peruvian people that their culture is "wrong," "we just want to tell people we're helping the frog to not go extinct," Weaver says.
"Our goal is to go in, get the animal in captivity, and see if we can reproduce it there," he says. This would create an assurance population in case the species continues to decline in the wild.
Toward that end the Denver Zoo helped design and fund an amphibian exhibit at the Huachipa Zoo in Lima. The exhibit, which aims to educate the public about the plight of South American amphibians and teach guests what they can do to save them, includes some wild-caught Lake Titicaca frogs.
Weaver says the Denver team came to Lima in December 2010 to help with final preparation for the exhibit. "The frogs had previously been kept in a lab at a constant temperature and pH," Weaver says. But after making a few adjustments for the exhibit to raise both the temperature and pH slightly the specimens started to reproduce. One of the frogs laid eggs, and five tadpoles hatched. "We did lose the tadpoles, but from an amphibian biologist point of view, getting them to produce eggs and spawn is a huge obstacle to get over, and we did that," Weaver says. "We can learn and replicate and hopefully get to the point where captured propagation is figured out."
Getting the right conditions for breeding and tadpole survival is difficult because there is so much variety in the conditions different amphibian species require for successful reproduction. "Sometimes we have no idea how species reproduce," Weaver says. "We try to replicate what we see in their natural habitat," but even that is a bit of a guessing game.
"We probably didn't have the perfect conditions for the tadpoles," he says. "It's a learning curve. The water could have been too clean. You have to figure out the right conditions." He says the fact that only a small number of eggs hatched indicates that they were close, but not quite there. "The tadpoles did last for two weeks," he says. "Next time we're going to have better success."
The Denver Zoo will continue to assist with the captive breeding program, and later this year will help to survey Lake Titicaca and the surrounding area to identify local species and their ranges. They will also be looking for evidence of the deadly chytrid fungus, which is devastating amphibian populations worldwide but has not yet been seen in the Lake Titicaca frog, although it has been found in nearby toad species.
Photo: A young Lake Titicaca frog, courtesy of the Denver Zoo