The European fire-bellied toad (Bombina bombina) is a species of fire-bellied toad native to eastern parts of mainland Europe, where it can be found near waterbodies such as ponds and marshes. It is known for its red colored belly used to ward off predators, an example of aposematism, and its distinctive "whoop" call.
Description
The European fire-bellied toad is a medium-sized frog, growing up to approximately .
There is an introduced population of European fire-bellied toads in Lorraine, France, over away from their natural range in eastern Germany. This population was first discovered in 2009 in Moselle but has since been found in several other nearby locations up to away, which suggests they were moved by humans intentionally. They can potentially impact the local yellow-bellied toads through hybridization.
While they are listed as "Least Concern" by the IUCN, this frog has been suffering some losses throughout its range. For example, 15 known breeding populations of these frogs were identified in Denmark in 1974, but by 1988 only 8 of those populations remained. In the Puszcza Romincka Landscape Park in Poland, the fire-bellied toad was described as uncommon, rare in the Coastal Landscape Park, and in an amphibian survey in Warsaw the fire-bellied toad only made up 9% of the observed species. However, in some areas they are recovering through human intervention, such as in Funen County, Denmark, where dozens of ponds were dug for the frogs to live and breed in, increasing their population approximately five-fold in a decade.
Ecology
This frog generally prefers to live in lowland areas such as ponds and marshes without too much woody vegetation. In return, the frogs are preyed on by many other animals such as snakes and birds, while tadpoles are eaten by leeches and fish.
They will typically hibernate once temperatures dip down to , during which they burrow into soil or a rotting log and remain in a state of torpor until spring. and is usually done at night time or early morning, where females will deposit up to 15 to 40 eggs depending on their size. Tadpoles are born in about a week and develop for approximately a month before metamorphosing at a size of about ). They emerged from an ancient divergence event, however they continue to hybridise where they overlap geographically. As the glaciers receded, both species spread out to the rest of Europe but hybridized and competed with each other until B. bombina occupied the lowlands and B. variegata the higher altitudes.
While the two frogs hybridize in narrow hybrid zones of approximately wide, they generally avoid it by differing in their morphology and behavior. B. bombina prefers to breed in lowland seasonal ponds, such as wet meadows and floodplains, but ones that are still close to nearby permanent waterbodies. On the other hand, B. variegata prefers to breed in higher elevations in ephemeral ponds that are quick to dry up. Additionally, B. variegata is unable to sing as loudly as B. bombina due to their lack of internal vocal sacs, which forces them to find other breeding ponds without the other species of fire-bellied toad. and B. orientalis – B. bombina produces bombinins. The H. Michl group in Vienna were the first to study B. bombina and B. variegata, first publishing a partial bombinin amino acid sequence in Kiss & Michl 1962. These two species produce and subsequently other prokineticins have been isolated from other species in the genus, and predicted in Rana temporaria and Pelophylax esculentus.