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Subterranean habitats

Subterranean habitats of Velebit

Even though deep pits are among the National Park’s greatest treasures, they remain hidden from most visitors. A number of speleologists, from a variety of speleological societies from Croatia and abroad, continuously explore the pits of Northern Velebit. Every year, their explorations result in new findings about the values of our karst underground.

The subterranean areas have conditions completely different from those on the surface. The normal temperature is several degrees above zero, the moisture content is high and it is completely dark. All these conditions are very stable, which is the main feature of the underworld. The part of the subterranean area close to the entrance is a transitional zone influenced by the conditions on the surface, so the variations here are greater than in deeper areas.

The underground of Velebit

Plants and other organisms that receive energy directly from the sun are not adapted to underground life. However, some plants, mosses and algae which do not require much light can be found underground close to the surface where some light enters the underworld. Since there are no plants underground, all food in subterranean habitats comes from the surface.
Animals use subterranean spaces with varied intensity. Some use them as shelter from predators and adverse weather, like some bat species that use the underground for hibernating in the winter and for spending the day. Other animals living in underground spaces can also be found in other dark, damp places.

However, the true subterranean animal species live exclusively in caves and pits, and can be immediately recognized by missing or weak eyes and body colouration, because pigments and organs of vision are redundant in total darkness. At the same time, food is very scarce and it is therefore extremely important for underground animals not to squander food and energy on production of unnecessary molecules and organs. These animals often have very slow metabolism, which allows them to survive with minimal amounts of food and prolonged starvation. A slow metabolism leads to a long life and slow breeding. Subterranean animals are coping well in the dark thanks to a highly developed sense of smell and touch. These senses are often manifested in form of prolonged antennae and legs that carry more sensory hairs.

Brown long eared

Almost all underground features discovered in the area of the Park are pits – vertical underground spaces. They are not as convenient for bats as caves, which is why no maternity colonies have been discovered here. However bats were found to hibernate in pits during the winter, although pits are not used as mass hibernation sites. Some of the recorded species are the lesser mouse-eared bat, the brown long-eared bat and the northern bat.

The majority of true underground animals are invertebrates. These are different groups of animals, often unfamiliar to the general public, such as beetles, earwigs, springtails, spiders, pseudoscorpions, isopods, polychaetes and others. They live in several different habitats within the underground: on land, in a thin layer of water that trickles down the walls and never dries out, in water, and on bat droppings or guano, a special type of underground habitat.


A wealth of fauna in the deep pits of Northern Velebit has been discovered in sporadic explorations to date. Given the distinctiveness and isolation of their habitats, a great majority (around 70%) of the subterranean species are endemic. Thirteen aquatic and 23 terrestrial organisms, all of them exclusively subterranean, have been identified in Lukina jama – Trojama alone. Unsurprisingly, given that the area is still unexplored, many new species have been identified.

Spelaeodromus pluto en

The Meštrov´s leech (Croatobranchus mestrovi), so far discovered only in four deep pits in Northern Velebit National Park, is an endemic species. These leeches grow up to 4.5 cm and are probably predators like their aboveground counterparts. Surprisingly, another leech species was discovered in Lubuška jama and in Lukina jama – Trojama, whose analysis is still in progress. The Dinaric tube worm (Marifugia cavatica) is the only freshwater subterranean tube worm in the world, and a species endemic to the Dinarides. A colony of Northern Dinaric Cave Clam (Congeria jalzici), a tertiary relict endemic to north-western Dinarides, was discovered in the syphon of Lukina jama – Trojama. This is the only freshwater bivalve species adapted to subterranean life. The discovery of the Ogulin Cave Sponge (Eunapius subterraneus), widely present around the city of Ogulin, in Lukina jama – Trojama was also surprising. The only freshwater subterranean sponge in the world, this species is also endemic to Croatia. Geophilus hadesi, a new centipede species, was also discovered in Lukina jama – Trojama, at the depth of almost 1000 m, which makes it the world’s deepest-dwelling centipede. The dipteran Cave Hajdi (Troglocladius hajdi) is the first known flying troglobiont (an organism fully adapted to subterranean life), found at depths greater than 800 m, also in Lukina jama – Trojama. This is the only known insect fully adapted to subterranean life that has also retained the ability to fly.

Velebit amphibious babura

The Park’s underground fauna is explored intensively, and new species and genera are discovered all the time.

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