Hrvatska posta issued a set of three stamp depicting amphibian representatives of Croatian fauna – fire-bellied toad, fire salamander and olm.
Fire-bellied toad is an amphibian living in lowland habitats throughout central and east Europe. It can be found in lakes, ponds and in flooding lowlands overgrown by thick vegetation. Despite of the adjective "fire-bellied" in its name, the raw skin on the back of an adult toad is usually olive green in colour with big dark patches. Only when it gets into trouble the orange to red colour characteristic for its belly becomes distinct on black background. The toad will turn on its back and push its belly upwards in order to warn the assailant of the poisonous substance it sends out through its skin. Though, in spite of this, some vertebrates feed on fire-bellied toad, especially birds. Although at world scale it is not an endangered species and falls in the category of the least endangered species it is strictly protected in Croatia because it is threatened to disappear from its natural habitat due to urbanization and agriculture development.
Fire salamanders are spread in central and south Europe, north-west Africa and in the Middle East. It is characterized by its black body covered with yellow spots or lines. It lives in moist and shadowy habitats, like deciduous woods, most often on hilly ground and in mountainous areas near water. This slow animal is mainly active during night, though on rainy days it can be seen also at daytime. Salamander feeds on insect larvae, snails, spiders and other invertebrates that live on the ground in woods. In the back of his head and in the four rows along his body it has got venomous glands whose poison serves as protection from assaulters and provokes irritation of nose and mouth but is not dangerous for man. Most animals avoid the fire salamander because of its warning colours. Salamanders are very sensitive to the contamination and destruction of their habitat.
Olm (proteus) inhabits only fresh water of the karst underground of Dinaric Mountains and is an endemic species of Dinaric karst. Though a real underground amphibian, olm can also be found on earth’s surface, when brought by an underground torrent. It is well adapted to specific underground world. Its eyes are undeveloped (rudimentary) and covered with skin layer while its other sensors are very well developed. It is a very interesting fact that this animal, so well adapted to the underground world, when exposed to outside conditions can get darker skin and can develop the sense of sight. Olm is unique in many aspects. It is an amphibian with the longest lifespan − it can live up to 100 years. It stays forever young-looking since it preserves the look of larvae during its whole life. This phenomenon is called neoteny and can be seen in olm on its outer gills. It is the only European amphibian adapted to life underground. About 30 centimeters long, it is the biggest cave animal in the world. In the Republic of Croatia it is strictly protected and globally it is considered an endangered species.