The wealth of habitats that characterize the Karst is also reflected in the high biodiversity of its fauna. This condition is even more accentuated within the Reserve thanks to the greater water availability determined by the presence of the karst lakes of Doberdò and Pietrarossa.
The life of some species that need fresh and humid environments revolves around the wetlands of these lakes. Remarkable the presence of reptiles and amphibians among which we remember the olm (Proteus anguinus), a urodel strictly specialized to live in the underground waters of karst cavities and therefore hardly visible on the surface.
The fish community is characterized by fish, especially cyprinids, capable of withstanding large thermal variations in temperature and strong decreases in dissolved oxygen.
The protected area also represents an important site for a large number of bird species, at least 190 from recent monitoring, many of which are of Community interest under the EC 79/409 Bird Directive. To highlight the presence of 6 species of Picidae, including the green woodpecker (Picus canus) and the black woodpecker (Dryocopus martius).
The population of invertebrates in the Reserve is very rich because, in addition to the communities of terrestrial ecosystems (scrub, heath, rocky outcrops, etc.), there are also those related to underground environments (caves and cavities) and fresh water.
Protozoa, rotifers, crustaceans, molluscs and insects form a basic element of the food chain of each of these ecosystems.
Mammals include some rare or localized species such as the skunk (Mustela putorius), the golden jackal (Canis aureus) and the wild cat (Felis silvestris). The numerous caves, deriving from the phenomenon of karst phenomena, host a rich community of bats. Among these there are common species such as the greater rhinolophus (Rhinolophus ferrumequinum) or the noctule (Nyctalus n. Noctula) others, such as the Blasius rhinolophus (Rhinolophus b. Blasii) are to be considered rare, perhaps extinct.
The symbol of the Reserve is the eastern hedgehog (Erinaceus concolor roumanicus), whose distribution in Eastern Europe finds its western limit in this territory.