The snout-vent length of males and females reaches only 45 (53) mm, with the Central European animals usually remaining smaller. This makes toads the smallest frogs in Central Europe, along with the European tree frog and the more closely related common midwife toad. The flat head with eyes relatively close together, the overall flattened body, the absence of externally visible tympanic membranes and ear glands (parotids) as well as the heart-shaped to triangular pupils are conspicuous in comparison to true Bufonidae. At mating time, males can be distinguished from females by dark nuptial padss on the forearm and first two fingers, and they also possess large throat bladders (unlike the yellow-bellied toad) that are visible when calling.
The upperparts of the body are covered with flat tubercles that have small black horned spines (not as distinct as in the yellow-bellied toad), light to dark gray or grayish brown with dark spots. Many individuals also have green neck spots. The underparts, including the insides of the arms and legs, are dark gray to black with conspicuous orange to red spots, sometimes occupying only one-fifth of the surface, but in extreme cases occupying the largest proportion. Most often, the proportion of reddish spots is slightly less than 50 percent. The darker areas are covered with many white spots. Five types of glands occur in the skin, including venom and mucus glands. The density of glands is greatest in the head area and decreases toward the end of the body. Fire-bellied toads have a color change and can adapt their dorsal coloration to light or dark backgrounds. The color change occurs only in the base coloration, the dark spots do not change.
The innermost fingers and toes, and overall the tips of the limbs, are not spotted with color, unlike the yellow-bellied toad. The ventral pattern of markings is individual like a fingerprint. When threatened, the fire-bellied toad forms a hollow back and bends its arms and legs upwards so that the red coloring of the underside is partially revealed. This so-called "barge position" or toad reflex is intended to serve as a warning signal to predators ("Caution, poisonous/inedible!").
Preferred biotopes are sunny, vegetation-rich, fish-free shallow waters with strong seasonal water level dynamics (seasonal flooding); these are colonized from spring to fall. In September/October, the return migration to the wintering grounds takes place over distances of up to one kilometer. Wintering sites are mainly woody plants with dead wood and foliage and occasionally reading stone piles. Reproductive success is subject to strong annual fluctuations, depending on temperature and precipitation.
The text is a translation of an excerpt from Wikipedia (https://de.wikipedia.org/wiki/Rotbauchunke). On wikipedia the text is available under a „Creative Commons Attribution/Share Alike“ licence. Status: 25 June 2021