By the early twentieth century, Western science had determined that giant amphibians other than salamanders were nothing more than a relic of the prehistoric past, until the 1906 discovery of the world's largest frog in remote Africa. The Goliath Frog is a former cryptid that is the largest extant anuran on Earth. Karl Shunker, a world leading cryptozoologist, stated that its discovery was "...one of the most dramatic amphibian discoveries of all time..." The largest known specimens can grow up to 33 cm (13 in) in length from snout to vent, and weighs up to 3 kg (7 lb). It has a relatively small habitat range, mainly from Cameroon to Equatorial Guinea. Its numbers are dwindling due to habitat destruction and its collection for consumption and the pet trade. 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 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. Goliath frogs were considered to be a source of food in some parts of west Africa. They were also highly exported to zoos and animal dealers to be sold as pets. Unfortunately, these frogs fail to thrive in captivity and almost never reproduce there. Due to their classification as an endangered species, the Equatorial Guinean government has declared that no more than 300 goliaths may be exported out of the country per year, due to conservation reasons. The goliath frog can live up to 15 years in the wild. In captivity, they can live up to 21 years. It is preyed upon by snakes, Nile crocodiles, and Nile monitors.