The fire-bellied toad (Bombina bombina) is characterised by its orange-black colouration of the belly. The orange spots are small and separated from each other, white spots can be observed on the black-coloured underside. Colour on the back can variate from brown, grey to olive tones. The skin is covered with small warts that are rather rounded than pointed. They have a heart-shaped eye pupil, no external eardrum and no parotid glands. During spring and summer, they are active day and night. During the mating season, males vocalize to attract females by inflating the front of the body and throat while floating on the water surface. The frequency of calls (uuu – uuu – uuu) in fire-bellied toad is 18 times per minute. The fire-bellied toad has internal vocal sacs, so it sounds louder than the yellow-bellied toad. During the mating season, mature males grow brown or black nuptial pads on the first two fingers and the inner surface of the forearms, helping them to better grip females during amplexus. The female may lay more than 300 eggs in a season, which are attached to aquatic plants in small row-shaped clutches that contain up to 30 eggs. Tadpoles are hatched from eggs within a few days and in about a month metamorphose into juveniles that disperse on land.
The fire-bellied toad is widely distributed in Europe, in large parts of Central, Eastern and South-Eastern Europe. Isolated occurrences in Denmark and South Sweden represent its Northern limit. German populations inhabit the most western part of the core area. Slovenian populations are the southwesternmost in Continental Region, where they all form a hybrid zone with a yellow-bellied toad.
The fire-bellied toad is an indicator of preserved lowland habitats, which are important for many plants and animals. They are inhabitants of sunny floodplain meadows, pastures, forest edges in lowland floodplains and river floodplains. They reproduce in larger permanent and stagnant waters like ponds, which do not dry out, have a lot of underwater vegetation and are free of fish. The fire-bellied toad may occasionally be found in temporary waters but prefers places with a good growth of subaquatic vegetation. They hibernate on the land and maybe found under stones and logs and among roots.
Populations of fire-bellied toads are under significant decline in Slovenia, Denmark and Germany. The main reason is due to habitat loss and degradation of wetlands and terrestrial habitats as a result of the intensification of the agricultural land and forests. The species is increasingly threatened by the disappearance and fragmentation of suitable terrestrial and aquatic habitats due to the drying up of floodplains, the regulation of watercourses, changes of water regime, backfilling of stagnant waters, introducing fish in aquatic habitats, water pollution, increased use of pesticides, herbicides and fertilizers in agriculture.
Interesting facts about fire-bellied and yellow-bellied toads
In areas where distributions of fire-bellied and yellow-bellied toads overlap, the two species successfully hybridize so that the entire contact area represents the so-called hybrid zone, where individuals with intermediate characteristics of both species can be found. Hybrids are usually morphologically similar to one of the parent species and are difficult to distinguish from the parent species by unprofessional. The whole Slovenian fire-bellied toad distribution range is in the hybrid zone.
Fire-bellied and yellow-bellied toads have poison glands in the warty skin. Potential predators are warned of their toxicity by the warning colouration on the belly, with the characteristic “unkenreflex” and playing dead. In danger, they throw themself on the back and show a mottled and vividly coloured belly to the predator. The anterior limbs are usually placed over the eyes and the posterior limbs are rigidly stretched upward. If the predator ignores the warning and the skin secretion comes in contact with their mucous tissue, it causes burning, tearing and sneezing, which is likely to be avoided at subsequent meetings.
Interestingly, adult specimens of both fire-bellied and yellow-bellied toads cannot stretch a tongue out of their mouth, so they don’t hunt flying insects. They rather pick up those that fall into the water or predate smaller insects and ground animals at night on land.