Conservation report
This month, shines the spotlight on the largest frog in the world.
The Goliath frog
What is known about the species?
This uncommon and skittish amphibian is found in southern Cameroon and Equatorial Guinea, and lives in and along rainforest streams. It is threatened by hunting for the bushmeat trade, and its natural habitat is becoming more degraded and fragmented. Our study was focusing on the food of Goliath frog tadpoles when we heard about the adults’ nest-building behaviour.
What did your research reveal?
Rather than relying on one plant (as was previously reported), tadpoles feed on various food sources. Of course, our most spectacular discovery was that Goliaths construct nests for spawning, most likely to create predator-free breeding sites. It is the first example of pond-building in an African amphibian that we know of and could explain why they are so large.
How big are these frogs?
Males can weigh 3kg and measure up to 34cm in body length (60cm if you include their legs). We think the frogs remove leaves and large stones from nest sites before the female lays eggs, to check for predators. The species is capable of moving objects that weigh up to 2kg, but most items they remove are small. They likely build their nests near torrent rivers to ensure their offspring escape predation by fish and shrimps.
Why were the nests clustered?
We don’t know yet, but our speculation is, that they may belong to one male attracting different females to the nest. Goliath frogs most likely use different nests during different parts of the season. Depending on fluctuating levels of the river, nests may become nonfunctional because the river floats them. The amphibians use three different nest types, probably to adapt to changing conditions throughout the season.
What next?
We would like to know how they make their decision to use which nest type and when; if it is always the same or different frogs using the nests; if it is the male or female guarding the nests and also if this behaviour can be observed in all populations or if other populations behave differently. Jo Price
MARK-OLIVER RÖDEL is curator of herpetology at the Berlin Museum of Natural History.
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