The Quest for Giant Treefrog Tadpoles

The Príncipe Giant Treefrog is the largest treefrog in Africa and can only be found on the tiny island of Príncipe. Photo by Andrew Stanbridge.


With the recent discovery of offshore oil, São Toméans will soon face the challenge of reconciling rapid economic development with preserving their natural heritage.  Young Explorer Rayna Bell will return to the island with a team of expert scientists to discover just how many species occupy the habitat and how rare and irreplaceable they might be.


Growing up in northern California, I never had any trouble finding tadpoles, but this past week in São Tomé and Príncipe has made me appreciate how elusive they can be! The little kid version of me would be happy finding just about anything, but on this expedition we’re specifically looking for tadpoles of the largest treefrog species in Africa: the Príncipe Giant Treefrog (Leptopelis palmatus). Although the adults are relatively easy to spot thanks to their size, the tadpoles have evaded biologist Bob Drewes for over a decade. Our motivation for finding them is to help us identify what types of habitat this endemic species relies on, but after many years of coming up short, it’s also become a matter of personal pride for Bob.

Most frogs lay their eggs in or near water and then tadpoles hatch out several days later. So to find tadpoles, all you have to do is find where the adults are breeding. In our case, the Príncipe Giant Treefrog is part of a family of frogs that lay their eggs on land, and when the tadpoles hatch they make their way to a body of water. This means the tadpoles could be just about anywhere, so we spent the past week looking in streams and rivers of all sizes, in ditches, in puddles, and even in water fountains. Nothing.

Biologists Bob Drewes and Rayna Bell searching for tadpoles of the Príncipe Giant Treefrog. Photo by Andrew Stanbridge.
Biologists Bob Drewes and Rayna Bell searching for tadpoles of the Príncipe Giant Treefrog. Photo by Andrew Stanbridge.


Although we may not be looking in the right places, there is also the possibility that this species doesn’t even have tadpoles, which is true of so-called “direct-developing” frogs that skip the tadpole life stage entirely. Instead, fully formed miniature frogs hatch out of eggs. For now, I think we’re ready to throw in the towel and try again next year.

Click here to watch Bob and Rayna take a closer look at what appears to be a tiny tadpole only to discover that it is actually a very small fish. (Video by Andrew Stanbridge)


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Meet the Author
Rayna is a graduate student in ecology and evolutionary biology at Cornell University studying diversification and conservation of African reedfrogs. When she's not in the field or planning her next expedition, Rayna spends her time in the genetics lab and teaching biology to undergrads at Cornell.