Amphibians
Titicaca Water Frog
Telmatobius culeus · also called Titicaca water frog, Titicaca scrotum frog
The Titicaca water frog is a frog that never leaves the water and barely uses its lungs. It lives on the bed of a single freezing Andean lake, breathing through great sagging folds of skin, and it is being pushed toward extinction by pollution and by a market for frogs blended into a “health” drink.
Overview
The Titicaca water frog is found only in Lake Titicaca and a few connected waters on the Peru–Bolivia border, at 3,810 metres. It is one of the most fully aquatic frogs in the world — it lives its entire life submerged, from the shallows down to depths of over 100 metres, and hunts amphipods, snails, insect larvae, and small fish on the lake bottom.
Built for cold, thin-aired water
High-altitude lake water holds little oxygen, and this frog has an unusual set of adaptations to cope:
- Loose, baggy skin folds over the body and legs, maximising the surface for absorbing oxygen from the water
- Reduced lungs — it rarely surfaces
- Small, densely packed red blood cells and the lowest metabolic rate ever measured in an amphibian
- A habit of doing “push-ups” on the bottom to move fresh water past its skin when oxygen drops
Historical reports, including from a 1970s Cousteau expedition, describe frogs up to half a metre outstretched; most seen today are far smaller.
“Frog juice”
In Peru and Bolivia, live frogs are skinned and blended whole into jugo de rana — “frog juice” — sold as a folk tonic for tiredness, low libido, and chest complaints. There is no evidence it works, but demand is high, and frogs are trafficked from the lake by the sackful to city markets.
Status
The Titicaca water frog is Critically Endangered, down an estimated 80%+ in three generations. Alongside the harvest for frog juice, untreated sewage and mining pollution entering the lake have caused mass die-offs — one 2016 event killed an estimated 10,000 frogs — and introduced trout and the chytrid fungus add further pressure. With its whole range confined to one lake, it has nowhere else to go; captive-breeding and community programmes are its main lifeline.
Titicaca Water Frog: common questions
Why does the Titicaca water frog have all that loose skin?
It is a breathing adaptation. The frog lives permanently in cold water nearly four kilometres above sea level, where the air — and therefore the water's dissolved oxygen — is thin. A normal frog would come to the surface to gulp air, but this species almost never does; its lungs are shrunken and it takes up oxygen directly across its skin. The deeply folded, baggy skin dramatically increases the surface area available for that gas exchange, so the more excess skin a frog has, the more oxygen it can absorb. When oxygen gets very low, the frog also bobs up and down on its short legs to push fresh water over the folds.
Is it really the "scrotum frog"?
That is a real, if crude, common name, coined because the sagging, wrinkled skin folds are reminiscent of scrotal skin. Jacques Cousteau's 1970s expedition to Lake Titicaca, which reported enormous frogs on the deep lake bed, brought the animal to wider attention. The name stuck in popular usage, though "Titicaca water frog" is the standard one. The extremely large sizes Cousteau's team described (up to half a metre with the legs stretched) are at the far upper limit and most frogs seen today are much smaller, partly because the biggest, oldest animals have been fished out.
What is "frog juice" and how does it affect the species?
In parts of Peru and Bolivia, live Titicaca water frogs are skinned and blended whole — with ingredients like honey, maca root, and aloe — into a drink called jugo de rana, sold at markets and stalls as a remedy for fatigue, low libido, bronchitis, and "weak blood." There is no medical evidence it does any of this. Demand is high enough that frogs are collected illegally from the lake by the sack and trafficked to cities, and this harvest, on top of pollution, is a major driver of the species' collapse. Conservation groups are working with local communities on captive breeding and alternative livelihoods.
What else is killing the Titicaca water frog?
Lake Titicaca receives untreated sewage and mining runoff from the growing cities and industry around it, and periodic pollution events combined with warm, still conditions have caused mass die-offs — one 2016 event left an estimated 10,000 dead frogs along a single river mouth. Introduced trout eat the tadpoles and young frogs and compete with adults, and the chytrid fungus is present in the population. The frog's entire world is one lake, so it has nowhere to retreat to.