Yellow–Bellied Toad

Tympanic membrane absent. Transversal processes of the vertebra sacralis notably widened. Pupil of the eye triangular. No male resonators. Skin tuberculate. Dorsal tubercles acute and relatively high. Ventral tubercles small and scarce in number. Dorsal surface dark-olive, with small dark spots. Belly yellow, sometimes orange, with large dark spots, white points absent or rare. On the belly, the bright coloration exceeds the dark coloration in area. The inner surface of the leg is covered with bright spots which are large and fused on the inner surface of the thigh. Tips of toes bright. In contrast with the female, the male has nuptial pads on the 1st, 2nd and 3rd fingers and, during the breeding season, on the inner surface of the forearm. Majority of these characters separate B. variegata from B. bombina. However, morphological characters probably have unequal taxonomic value and only their combined use may be effective for practical identification.

The species inhabits Central and Southern Europe except for the southwestern part. The western margin of the range runs through Germany (Lower Saxony, North Rhine-Westphalia) to The Netherlands (Limburg Province), Belgium and France in the south. The species lives in Switzerland and Italy (a relic population occurs on Etna Mountain, Sicilia). In Greece, the species lives southwards to Peloponnes Peninsula. The northern margin of the range runs from Germany to Czech Republic, Southern Poland, Western Ukraine (Carpathians), Romania and Eastern Bulgaria. Several subspecies are recognized. Bombina variegata variegata inhabits the main part of the range, B. variegata kolombatovici lives in Yugoslavia (Dalmatia and Montenegro), B. variegata pachypus in Italia, B. variegata scabra in Montenegro, Albania, Greece and Bulgaria.There is a contact zone with the related species, the Fire-Bellied Toad (Bombina bombina). This zone extends over the Southern Poland, Czech Republic, Austria, Hungary, Bulgaria, Romania, Yugoslavia, Greece and Western Ukraine.Bombina variegata lives mainly in foothills and mountains: in coniferous, deciduous and mixed forests, bushlands and meadows, floodplains, grasslands etc. At low elevations the toad lives in deciduous forests whereas in highlands it inhabits coniferous forests, highland glades and the upper forest margins. It uses various types of water bodies, including lakes, ponds, swamps, rivers and stream pools (sometimes streams with swift current), springs etc. Its requirements to water quality are relatively low. The toad occurs even in highly polluted wetlands, even waters with high concentrations of hydrogen sulfide and salts.

The Yellow-Bellied Toad is usually not a rare amphibian. Its population density in some suitable sites is higher than one specimen per few square meters, up to one specimen per 0.02 m2. In the Carpathians, it is the most common amphibian species inhabiting the broadest range of habitats.Hibernation begins at the end of September - beginning of October and ends in March - May, depending on elevation. The toads overwinter in burrows, holes under stones and logs. In thermal springs, the toads may be active in winter. Reproduction starts 5-10 days after entering the water and extends to August. Amplexus is pelvic. Amplectant specimens and the spawn are often observed at the same time and in wetlands where conspecific tadpoles undergo their metamorphosis. Along with a wide diversity of breeding pool types, this trait increases the variety of habitats used by the toad populations. Sometimes heavy rains in summer may be followed by intensive spawning of B. variegata in small wetlands. The male mating call is similar to that of B. bombina, but is quieter and higher. The clutch consists of 45-100 (or more) eggs deposited in portions.In contrast to B. bombina, the Yellow-Bellied Toad eats mainly terrestrial arthropods. This composition of diet corresponds with its more terrestrial habits. Aquatic invertebrates, e.g. Gammaridae, are eaten mostly on the stream banks. The diet changes with age during the postmetamorphic period of life and includes an increase in the selection of larger prey. However, no age changes are known in the proportions of aquatic and terrestrial prey in the diet.

During the last 10-20 years anthropogenic pressure has led to the extinction of B. variegata from at least 13 localities in the Zakarpatskaya and Lvov Provinces of Ukraine. Destruction of natural habitats and urbanization leads to population declines.

Evidently, anthropogenic influences are more important in the toad's population declines than natural biotic factors. Nevertheless, the species is common in human neighborhood and occurs even in wetlands highly polluted by humans. It lives there not only in the countryside but also in some urban forest parks, using artificial lakes and ponds. This is related to its opportunistic habits and high tolerance to pollution of environment.