Karst areas like Učka and Ćićarija are particularly valuable and interesting for their subterranean fauna, which is predominantly endemic and protected by law.Approximately 200 caves, pits and other karst phenomena have been registered within the area of Učka Nature Park.
Thirty-five of these have been researched from the biospeleological perspective so far, the most interesting being the natural underground cavern in the Učka Tunnel. This cavern is the only place within the park where an endemic cave beetle has been identified - Croatodirus bozicevici. As many as 10 endemic subterranean specieshave been registered so far in the Učka and Ćićarija areas – particularly important is thedescription of a new species of troglobitic isopod Thaumatoniscellus speluncae.
Because of the sensitivity of the cave fauna, disturbing the environment in the high-altitude areas of Učka and Ćićarija can significantly endanger the survival of individual species, especially of those that are closely related to groundwater. Apart from the study of caves and pits, in the next period particular attention will be given to the study of water sources in the coastal area and in the hinterland of Učka.