The Goliath Frog (Conraua goliath)

Biologist Claude Miaud swabbing skin to determine presence of Chytrid fungus on a Goliath Frog | Photograph by Cyril Ruoso/Minden Pictures/Solent News & Photo Agency

Biologist Claude Miaud swabbing skin to determine presence of Chytrid fungus on a Goliath Frog | Photograph by Cyril Ruoso/Minden Pictures/Solent News & Photo Agency

The Conraua goliath is one of those species that most people with no interest in amphibians will have heard of because of its size. The 'biggest frog' factoid being an almost must for any pub quiz...or perhaps more realistically, for any pub quiz I would certainly enjoy.

I decided to write about it due to a dream. Yes, that's right, a dream. Not long ago I dreamt that I found a large C. goliath specimen in my garden and I was over the moon about it. I mean, a living and breathing Goliath Frog in my garden! In England! The downside of this dream was that in it, I was the only person able to see the frog. The dream version of my husband couldn't see it at all...oh, the frustration! The next day, I was telling my friend Steven Allain about my strange dream. Realistically, he's one of the only people in my day-to-day life who would truly appreciate the frustration that my dream-self was experiencing. We got talking about C. goliath and I then decided that I would write a post about it. Why not? If I believed in such things, I would say the dream was a sign and all that. So, here it it.

C. goliath tadpole | Photograph by Steve Atkin

C. goliath tadpole | Photograph by Steve Atkin

Most people will know that the C. goliath - commonly known as the Goliath Frog or Giant Slippery Frog - is the largest species of living frog on the planet. Records show that adults average at around 12 inches in length and 3 kg in weight. Curiously, although the adults of the species are carnivores, the tadpoles are herbivores. In fact, the C. goliath tadpole's early diet is rather restricted and made up mainly of the Diacraeia warmingii plant. Unfortunately, as the range of this plant is limited, the spread of the C. goliath in the wild is also restricted to parts of Equatorial Guinea and Cameroon. As adults, however, the C. goliath's size means that almost anything is a potential meal. A  few sources indicate that a researcher has found evidence of bats in the contents of a captured C. goliath individual's stomach. However limited the evidence may be, it does suggest that these frogs are able to catch bats to begin with...considering that this species can leap up to 10 feet, catching bats becomes a somewhat more believable feat.

Vendor showing his available C. goliath collection for sale in Cameroon | Photograph taken from The African Gourmet's website

Vendor showing his available C. goliath collection for sale in Cameroon | Photograph taken from The African Gourmet's website

Unlike most frog species, the males are usually bigger than the females. This may help explain another unusual characteristic of the species - males do not possess nuptial pads. Nuptial pads in male frogs are used to facilitate the grasping of the female during mating. Another curiosity in their biology is that although they have an acute sense of hearing, they do not possess vocal cords. Therefore, they do not produce sounds during the mating season as many other species of frogs do. C. goliath males will instead create round pools of shallow water by riverbanks and wrestle each other for the right to mate.

Their short mating season ranges from July to August and females will lay hundreds of eggs. Unlike other frog species, these eggs will receive no protection from the parents and the surviving tadpoles will take between 85-95 days to metamorphose into frogs. They rarely breed in the wild and captive-breeding is unfortunately also rarely successful. Furthermore, the Goliath Frog's meat is part of the diet of many African tribes and considered a delicacy by local people. Combined with the hunt for wild individuals in order to meet the demand of the pet trade, you will not be surprised to hear that this species is listed as endangered. 

To address this issue, Dr. Gonwouo Nono LeGrand and his team at the Cameroon Herpetology-Conservation Biology Foundation (CAMHERP-CBF) are working to tackle the threat of over-harvesting as well as habitat loss. The Global Wildlife Conservation (GWC) also supports the work being carried out by the CAMHERP-CBF and helps spread the word about their efforts. It is lovely to see businesses getting involved. A great example is a Vancouver based company,  Goliath Coffee, that sources all of its coffee from Cameroon showing its support for the cause. They even have an entire section of their website dedicated to it - check it out.  

If like me, you too like reading about this amazing frog, I have listed my main sources below. If you know of any other major projects aimed at the conservation of the Conraua goliath, do let me know! I'd love to hear from you. 

References & Sources:

  • Mikula, P. (2015). Fish and Amphibians as Bat Predators. European Journal of Ecology 1:66-75.
  • Soulsby, D. (2013). Animal Cannibalism: The Dark Side of Evolution. Sheffield, 5m Publishing.
  • Mattison, C. (2014). Nature Guide: Snakes and Other Reptiles and Amphibians. London, Dorling Kindersley.
  • Halliday, T. (2016). The Book of Frogs: A Life-Size Guide to Six Hundred Species From Around the World. Lewes, Ivy Press. 
  • Attenborough, D. (2008). Life in Cold Blood: A Natural History of Amphibians and Reptiles. BBC Books.
  • Dorcas, M. & Gobbons, W. (2011). Frogs: The Animal Answer Guide. Baltimore, The Johns Hopkins University Press.
  • Beltz, E. (2005). Frogs: Inside Their Remarkable World. New York, Firefly Books.