The goliath frog otherwise known as goliath bullfrog or giant slippery frog (Conraua goliath) is the largest living frog on Earth. Specimens can grow up to 33 centimetres (13 in) in length from snout to vent, and weigh up to 3.25 kilograms (7.2 lb). This species has a relatively small habitat range in Cameroon and Equatorial Guinea. Its numbers are dwindling due to habitat destruction and its collection for food and the pet trade.
In a sample of 15 individuals, weights ranged between 600 and 3,250 g (1.32 and 7.17 lb), and snout-vent lengths were between 17 and 32 cm (6.7 and 12.6 in). Their eyes can be nearly 2.5 cm (1.0 in) in diameter. The conspicuous tympanum has a diameter around 0.5 cm (0.20 in) and is separated from the eye by about 5 cm (2.0 in) in adults. Goliath frog eggs and tadpoles are about the same size as other frogs despite their very large adult form.
A lateral fold extends from the eye to the posterior portion of the tympanum. Toes are fully webbed, with large interdigital membranes extending down to the toe tips. The second toe is the longest. The skin on the dorsum and on top of the limbs is granular. Dorsal coloration is green sienna, while the abdomen and ventral part of the limbs are yellow/orange. They have acute hearing, but no vocal sac, and also lack nuptial pads.
Distribution and habitat
The goliath frog is normally found in and near fast-flowing rivers with sandy bottoms in the Middle African countries of Cameroon and Equatorial Guinea. These rivers are usually clear and highly oxygenated. Their actual range spans from the last 200 km (120 mi) of the Sanaga basin in Cameroon to the north to the last 50 km (31 mi) of the Benito River basin in Equatorial Guinea to the south. The river systems in which these frogs live are often found in dense, extremely humid areas with relatively high temperatures.
Ecology and behavior
Like most amphibians, water is vital for their reproduction. Because the goliath frog lacks a vocal sac, it does not produce mating calls, a behavior generally present in frogs and toads. Males construct spawning and breeding areas alongside and within rivers by pushing rocks into semicircular patterns. The egg masses consist of several hundred eggs, approximately 3.5 mm (0.14 in) each, attached to vegetation at the bottom of rivers. The need to construct nests for spawning in the slower pools of fast-moving water may also explain the goliath frog's large size, as larger frogs may be more successful at moving heavy objects when constructing their nests. Adults have also been shown to guard the nests at night. Larval development takes between 85 and 95 days.
Goliath tadpoles are herbivorous and feed on a single aquatic plant, Dicraeia warmingii (Podostemaceae), found only near waterfalls and rapids, which may help explain their restricted range. Adult goliath frogs feed on spiders, worms, and insects, such as dragonflies and locusts. They also eat smaller frogs, crabs, baby turtles, and young snakes. A bat reportedly was found in a goliath frog's stomach.
The primary threat to the goliath frog is hunting, as it is considered a food source in its native range. The IUCN has highlighted the need for conservation measures, in cooperation with local communities, to make sure the hunting is at sustainable levels. To a lesser extent they are also threatened by habitat loss and degradation. They were extensively exported to zoos and the pet trade, but have proven shy and nervous in captivity. Although captives may live longer than their wild counterparts, the species has not been bred in captivity. Due to their classification as an endangered species, the Equatorial Guinean government has declared that no more than 300 goliaths may be exported per year for the pet trade, but few now seem to be exported from this country.
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- "Goliath Frog". The American Museum of Natural History. 2007. Retrieved 9 February 2012.
- Sabater-Pi, J. (1985). "Contribution to the biology of the Giant Frog (Conraua goliath, Boulenger)". Amphibia-Reptilia. 6 (1): 143–153. doi:10.1163/156853885x00047.
- "True Frogs: Ranidae – Goaliath Frog(conraua Goliath): Species Accounts". Net Industries. 2008. Retrieved 9 February 2012.
- Mikula, P. (2015). "Fish and amphibians as bat predators". European Journal of Ecology. 1 (1): 71–80. doi:10.1515/eje-2015-0010.
- Indiviglio, Frank (31 January 2013). "The World's Largest Frog – Working with the Massive Goliath Frog". thatpetplace. Retrieved 4 November 2017.
- "Goliath Frog is a Disappearing Giant". Frogsource. Retrieved 4 November 2017.
Data related to Conraua goliath at Wikispecies
- Photos of goliath frogs with people at Queensland Frog Society
- Conraua goliath in the CalPhotos Photo Database, University of California, Berkeley
Media related to Conraua goliath at Wikimedia Commons