Cabinet of Freshwater Curiosities: Lake Titicaca ‘scrotum’ frog adapted to the high life

If you’re a long-time follower of the Freshwater Blog, you might remember our Cabinet of Freshwater Curiosities project from more than a decade ago. That website has since washed away down the rivers of time, but we thought it was the right moment to showcase our collection of curious freshwater plants and animals again. So keep your eyes peeled over the coming months as we dust off the Cabinet and celebrate the wonderful world of freshwater life!

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One of the largest frogs on the planet, the Lake Titicaca water frog makes one of the strangest fashion statements in the amphibian world. Its excessive skin folds have earned it the whimsical Latin name of Telmatobius culeus, or ‘aquatic scrotum’.

The ‘scrotum frog’s’ bizarre outfit is actually the perfect adaptation to the cold waters of its high-altitude home. This bottom-dwelling frog – which can live at depths of 100 metres – is only found in Lake Titicaca, 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. This adaptation protects the frog from the high levels of ultraviolet radiation found in the area. The species also benefits from a high number of small red blood cells, which efficiently deliver oxygen and remove carbon dioxide from its body tissues.

This 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.

Jacques Cousteau, searching Lake Titicaca for Inca treasure in the 1960s, was equally enthralled, reporting “thousands of millions” of the frogs, some almost 60cm 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 is 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.

In 2018, Bolivia and Peru signed a bilateral agreement to recover Lake Titicaca and protect the Titicaca water frog , outlining the priority actions that will protect the species across its range. In 2016, the Titicaca water frog was included in Appendix I of the CITES Convention, which restricts international trade of the animal.

“There have been some amazing champions working on the ground both in Bolivia and Peru to prevent the extinction of this species and to inspire the political will to join these efforts,” said Ariadne Angulo, co-chair of the IUCN SSC Amphibian Specialist Group.

“And we have been inspired by both governments working collaboratively with one another and hand-in-hand with conservation groups in recent years. Given the threats that the species continues to face, however, the efforts to date are the building blocks for what it is going to take to save the Titicaca water frog in the long-term.”