The world’s largest frog and the largest frog in Poland

Frogs are the most numerous group of amphibians on Earth – more than 7,800 species are known and new ones are still being discovered. They inhabit almost all continents, from the tropical forests of the Amazon to the mountain streams of Asia. Among them you will find both frogs smaller than a coin and true giants. The record holder in this world is the African shy goliath – the largest frog in the world, which can reach the size of a cat and weigh more than 3 kg. In Poland, we also have our own record-holder: the laughing frog.

The world’s largest frog – the shy goliath

The goliath frog – also called the giant slippery frog or Conraua goliath – is the largest anuran amphibian in the world. It can be found in the moist rainforests of West Africa. Its natural range includes southwestern Cameroon and the northern part of mainland Equatorial Guinea (Río Muni). There, among fast-flowing rivers, waterfalls and old-growth forest banks, goliaths have ideal living conditions – clean, well-oxygenated and slightly acidic water with a temperature of about 19.4°C.

What a goliath frog looks like, what it eats and how it reproduces

This African giant grows up to 32 cm in length (body, without legs), and its weight can exceed 3 kg, In goliath frogs it is usually the males that reach a larger size, which is an exception in the amphibian world. Their coloration is distinctive – the green-brown back, often with dark spots, contrasts with the intense yellow-orange underside of the body. Strongly muscled limbs and wide amniotic membranes enable this frog not only to swim effectively, but also to leap up to 3 meters.

The body of the goliath is flattened, the head is broad and triangular, the eyes are up to 2.5 cm in diameter, and the eardrum – important for the sense of hearing – reaches a diameter of 0.5 cm. Males, despite the lack of resonant sacs, are able to emit soft whistles, with which they attract females during the mating season. Goliaths lead a nocturnal lifestyle – during the day they are submerged in water, exposing only part of their heads to the surface, and after dark they come out on land in search of food.

Their diet includes a variety of prey – from insects, worms, spiders, scorpions and fish to other frogs and small mammals. In captivity, they have even been observed eating white mice. An interesting fact is that goliath tadpoles are strictly herbivorous and feed on only one aquatic plant: Dicraeia warmingii. This dependence on a specific food source means that their larval development can only take place under very specific environmental conditions.

The reproductive cycle of the goliath is equally unusual – males are polygynous and territorial, so they fight among themselves for dominance. During the mating season, males build special nesting pools: they clear stones and remove litter, and sometimes even dig hollows. Sometimes they move stones weighing half as much as they do. Females lay hundreds of eggs, which attach themselves to rocks or aquatic vegetation. After about 85-95 days, the tadpoles undergo transformation, and reach sexual maturity at 10-12 months of age. Goliaths can live 10-15 years in the wild, and up to 20 in captivity.

Goliath frog in danger of extinction

The goliath frog is a seriously endangered species. It has been on the IUCN Red List since 2004. Its population has dramatically declined – by more than 70 percent between 2004 and 2019. – mainly due to hunting, illegal trade, habitat degradation, logging, water pollution (especially pesticides) and dam construction. Although the export and harvest of frogs in Equatorial Guinea and Cameroon are regulated, local hunting pressure continues. The positive news, however, is that in 2022 they were rediscovered in Monte Alén National Park – they had been unseen there for nearly two decades.

The largest frog in Poland – the laughing stock

The laughing frog(Pelophylax ridibundus) is a true giant among Polish amphibians. It is the largest species of frog found in our country – adult females reach up to 17 cm in length. Although in terms of size it resembles the water frog ( Pelophylax cl. esculentus ), is noticeably more massive than it: it has a more stocky body, a broad head and stronger limbs. Its body is covered with olive-green or brownish skin with irregular dark spots, and a distinctive light line runs across its back.

The common pochard inhabits almost all of Europe, Asia Minor, Iran and northern Africa. In Poland, it is found primarily in the lowlands – in large numbers in Pomerania, Greater Poland, Mazovia and Lesser Poland. It prefers large, standing bodies of water, especially with lush vegetation. It falls into winter dormancy from September or October, burrowing into the bottom silt of bodies of water. It wakes up in spring – usually in March or April.

It leads a diurnal lifestyle. During the mating season – from April to June – males call females with a loud retching, using resonators at the head. They lay their eggs on the bottom of the tank or on aquatic plants, and the tadpoles metamorphose in autumn. Females are usually larger and more intensely colored than males.

The role of the laughing frog in nature

The laughing frog plays an important role in the aquatic ecosystem – it hunts insects, larvae, small invertebrates and even tadpoles and other amphibians. Interestingly, it belongs to the so-called green frog complex and can interbreed with other representatives of the genus Pelophylax, forming hybrids, such as the water frog. As a result, this species has a lot of adaptability and copes well in different environmental conditions. Nevertheless, the laughing frog needs clean, natural bodies of water, which we are running out of. In Poland, it is under strict species protection, and providing it with habitat is one of the key conditions for it to continue to occur in our landscape.

MAIN PHOTO: Sarawut/Adobe Stock