Living at 12,000 feet – Lake Titicaca “scrotum” frog adapted to the high life

Entirely aquatic and one of the largest frogs on the planet, growing up to the size of a salad plate, the Lake Titicaca water frog also makes one of the stranger fashion statements in the amphibian world. Its excessive skin folds, which look like someone put its skin through a taffy-puller and then sewed the result back on, have earned it the whimsical Latin name of Telmatobius culeus – “aquatic scrotum.”

The scrotum frog’s bizarre outfit is actually the perfect adaptation to the cold waters of its high-altitude home. The bottom-dwelling frog is only found in Lake Titicaca, often called the highest navigable lake in the world, sandwiched between Peru and Bolivia. The frog is entirely aquatic, living in the reed beds of the lake and its rivers. Avoiding the oxygen-depleted air, its ornate skin folds and abundance of capillaries allow it to absorb oxygen directly from the saturated water, making up for its tiny lung size and allowing it to stay permanently below the surface – which protects it from the high levels of ultraviolet radiation found in the area. It also benefits from a high number of small red blood cells, which efficiently deliver oxygen and remove carbon dioxide from its body tissues.

Illustration by P. Roetter, Bulletin of the Museum of Comparative Zoology

Illustration by P. Roetter, Bulletin of the Museum of Comparative Zoology

The oddball frog has fascinated people for centuries. Lake Titicaca frogs were believed to have special powers, particularly in bringing  rain: once carried in a ceramic pot to a hillside, the frogs would call in distress, which supposedly sounded to the gods like a plea for rain. Once the downpour began, the pot would overflow and the sacred animals would escape back to the lake. The frog also captured the imagination of its 1876 European discoverer, S.W. Garman – as witnessed by his choice of a name. Jacques Cousteau, searching Lake Titicaca for Inca treasure in the 1970s, was equally enthralled, reporting “thousands of millions” of the frogs, some almost 20 inches long.

These days, such giants are unlikely to be seen. Aside from global threats to amphibians such as the chytrid fungus and invasive species, in this case a trout that preys on its tadpoles, the Lake Titicaca water frog suffers from over-popularity. It is a favorite menu item at tourist restaurants around the lake, and is also taken to Lima markets – where it’s sold as an aphrodisiac. The frogs are skinned and then blended with water, maca (a local root vegetable) and honey into a juice, thought to be the cure for several ailments, including impotence. It is also collected as a pet or curiosity, while pollution, habitat loss, and overfishing of its main prey, the small fish known locally as ipsi, could also be pushing the critically endangered frog towards extinction.

In response, captive breeding programs have been established for the giant amphibians, both around Lake Titicaca and internationally. One possible plan is to farm the frogs for consumption, taking the pressure off those left in the wild, although this could subject the small population to increased risk of disease from large, densely-kept captive populations. Scientists from both Peru and Bolivia are studying the frog, to assess its ecology and feeding habits as a base for captive breeding.

ARKive video – Lake Titicaca frog

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