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The tomato frog

In 1875, a bright red, plumpy frog fell into the hands of French naturalist Alfred Grandidier during one of his many expeditions to Madagascar. A compatriot, who had settled as salesman at the eastcoast, was the one who had brought the frog: A certain Mister Guinet. The well-traveled Grandidier took the animal of this still unknown species to France and described it for the first time. Why he chose the name tomato frog (Dyscophus antongili or Dyscophus guineti) should be clear from first sight: The clumsy, round look and the natural color surely reminds one of a certain red vegetable. In Madagascar, the frog is called “Sahongogogno”, which onomatopoeic represents its calls.

CC BY-SA 2.5 Franco Andreone
Male of Dyscophus guineti, © by Franco Andreone CC BY-SA 2.5

Genders of the tomato frog are easy to differentiate: Only females become beautiful bright red or orange, while males have a yellowish back. The belly is pale in both genders. Females can reach sizes from nose-tip to the butt of almost 10 cm, with impressive weights of a good half pound. Males stay much smaller and with maximally 50 g much lighter, too.

There are exactly three species of tomato frogs: The “normal” tomato frog (Dyscophus antongili, namend after its main site of find, the bay of Antongil), the Sambava tomato frog (Dyscophus guineti, named after the first French man who found him) and the Antsouhy tomato frog (Dyscophus insularis, which is not described in this article). It is yet unclear whether the first two are separate species or if one might be just a color variation from the other species.

Originally, the tomato frog comes from Madagascar’s east coast. It only occurs here and nowhere else on Earth in wilderness. The northernmost habitat is Sambava, the most southern finding described is somewhere between Folagnaro and Farafangana along the southeast coast. Along the coast, you can find tomato frogs up to heights of 200 m onshore. But it is not that easy, because tomato frogs love to hide well, preferably buried in mud or soil. A pond or slow stream nearby building some stagnant water is their favorite habitat. The Sambava tomato frog prefers rainforests, while the normal tomato frog can be found in secondary vegetation, it even lives along garbage of villages, inside gardens and swamp-like areas or human-made ponds. In the night, it is much easier to find tomato frogs, since this is the time for them to go hunting small insects.

© by Franco Andreone CC BY-SA 2.5
Tadpole of Dyscophus antongili © by Franco Andreone CC BY-SA 2.5

Around the end of the rainy season, in February and March, mating time begins. Until them, there was a lot of precipitation yet, so there are optimum conditions for the offspring, which is bound to water. During mating season, the males call loudly from their water holes, and thus attract the females to come close. If one finds a matching female, he clings to her and falls into so-called Amplexus, a clasping reflex.

The sticky, black and white eggs that were fertilized during mating, are deposited in small ponds or other stagnant water and swim like a film on the water surface. One female can accomplish up to 1500 eggs per clutch, most abide more by 1000. Each egg is not larger than 2 millimeters. From these tiny eggs, chubby small tadpoles hatch after 36 hours. They are only a half centimeter in length, and feed by filtering the water around them. Of course, the tadpoles are a welcome prey for larger animals, so only few tadpoles succeed to become a frog. That is why the female lays so many eggs – the more tadpoles there are, the higher is the chance that some of them will survive. After one month, the tadpoles fulfill their metamorphosis into a small, yellow frog and get out of the water to begin life as terrestric animal. The adult colors become visible beginning from a body size of two centimeters. One knows from captive kept tomato frogs that they can live from six to ten years. Their conspecifics in Madagascar might surely not get that old facing all those dangers in the wild.

A sign in Maroantsetra that makes people aware of frog conservation

At IUCN red list, Dyscophus guineti is listed as least concern. It is quite interesting in fact that this tomato frog does not occur in any protected area of Madagascar – he adapts to the conditions his environment offers. Its sister species, Dyscophuis antongili, ist listed as near threatened. According to this, only the Sambava tomato frog is used for export to amphibian friends worldwide. For decades, the species has been popular among hobbyists for easy keeping.

Besides the threats from humans and habitat destruction, snakes and lemurs are another danger for tomato frogs. But the glowing bright colors of adult frogs scares many predators – and if the slightly poisonous secret on their skin is not enough to discourage another animal from eating the frog, it blows itself up to appear bigger. That big, it does not fit well into the predator’s mouth, and maybe is reprieved once again. In Maroantsetra, at the bay of Antongil, people try to do educate others about the tomato frog and get as much as possible locals aware of species conservation efforts. It is a hope to let these lovely red guys get a chance to survive.

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