Collapse dolines and their surroundings offer shelter to rare and endangered bird species and several bat species, and an extraordinary ecosystem that has developed due to particular geomorphologic and microclimatic conditions has been preserved. The underground is rich with several species of cave animals: both those living on land and those living in water.
As early as in 1887, Carlo Marchesetti provided a botanical description of the Škocjan Caves in a guidebook about this natural valuable feature. The deep collapse dolines surprise phytogeographers with their numerous kinds of frigophilous species and a variety of thermophilic, sub-Mediterranean species co-existing nearby.
In the area of the regional park, we find thermophilic species characteristic of sub-Mediterranean grassy areas and scrubs: karst hornbeam, Centaurea rupestris, Chrysopogon gryllus, Cleistogenes serotina, Digitalis Laevigata, Pulsatilla montana, Potentilla tommasiniana, Ruta divaricata etc.
The Park is the habitat of some endemic, rare or endangered species, which have also been entered in the red list of ferns and seed plants of Slovenia: Orobanche mutelii (the only habitat), Lamium wettsteinii (one of the two habitats), Campanula justiniana ("classical" location or locus classicus), Aconitum anthora, Hyssopus officinalis, Juniperus oxycedrus, Ranunculus pospichalii and Salvia officinalis.
The distinctiveness of the flora in Velika dolina is evidenced by species that grow here, relicts from the previous geological periods in the same sites. Glacial relics (relicts of the Ice Age flora), such as alpine auricula (Primula auricula), crusted saxifrage (Saxifraga crustata) and Kernera (Kernera saxatilis), are concentrated on the bottom of the collapse doline, just above the Reka River sinkhole. Some 40 metres higher, on the ceiling of the Schmidl Hall entrance, thermophilic relics (remnants from warmer periods) grow, i.e. maidenhair fern (Adianthum capillus-veneris), wild asparagus (Asparagus acutifolius), prickly juniper (Juniperus oxycedrus), and Tortella flavovirens moss. It is a unique natural phenomenon that such different relics thrive together.
Plants adapted to extreme light conditions live at the entrance to caves (Schmidl Hall, Tominceva Cave). The most common flowering plants include the common ivy (Hedera helix), wall lettuce (Mycelis muralis), Stellaria montana Pierrat and spreading pellitory (Parietaria judaica). Ferns include maidenhair spleenwort (Asplenium trichomanes) and Hart's-tongue (Phyllitis scolopendrium). The deepest parts of the cave entrance cave are inhabited only by some mosses and algae.
The first birds that one notices in Velika and Mala dolina are rock doves (Columba livia), flying overhead in flocks and nesting under the ceilings of the cave entrances. A small colony of less well-known alpine swifts (Tachymarptis melba) nests in the rock fissures below overhangs. The steep cliffs of collapse dolines offer periodical shelter and nesting places to the eagle owl (Bubo bubo), the peregrine falcon (Falco peregrinus) and the common raven (Corvus corax). The overhanging walls are a wintering site for coloured wallcreeper (Trichidroma muraria), otherwise an Alpine species, which feeds on spiders and small invertebrates hiding in rock fissures.
The co-existence of diverse habitats in the Park is evidenced by the presence of numerous forest and meadow bird species. Here we can find hygrophilous species of birds, such as the winter wren (Troglodytes troglodytes) on the bottom of collapse dolines, entirely thermophilic bird species, such as different kinds of yellowhammer (Emberiza), shrike (Lanius), larks and other open landscape bird species, the existence of which is nowadays greatly endangered due to rapid overgrowth on the once bare Karst hills.
Among mammals, we can see dormice occupying the caves or treetops that are very common in these parts. The fox and the badger have their places on the slopes of the Reka River gorge and the Sušica stream. Many bat species live in the Škocjan Caves, the most numerous being the Schreiber's long-fingered bat (Miniopterus schreibersii), the colony of which migrates between the Škocjan Caves and Predjama, as well as the long-fingered bat (Myotis capaccinii). In the past, each of these two colonies numbered over 1,000.
There are also some habitats underground. These spaces include rock fissures, underground Karst caves and narrow but interconnected spaces between grains of sand or gravel. All these spaces may be relatively dry or covered with water.
What are the living conditions like underground?
Darkness reigns and nothing is seen. There are other consequences as well: there are no green plants here that produce organic food on the surface. The food reaches the underground in small quantities in the form of detritus, organic particles resulting from the disintegration of dead organisms on the surface. Thus, a considerable scarcity of food is characteristic of the underground. However, such an enclosed space has its advantages, too. The general belief that the underground is cold is erroneous; there may be no summer there, but there is no winter either, and the temperatures are stable. Furthermore, the air is constantly humid which is advantageous for animals.
And who or what lives underground?
Bacteria and fungi are, of course, present in great numbers underground as they can be found every where there is something organic. Several modest and specially adapted animals feed on bacteria and fungi as well as the detritus. Atrophied useless parts, such as eyes and pigmentation are c characteristic of these animals. Sensory organs that do not require light, such as organs of smell, palps and others, are enlarged. In the same vein, some adapted subterranean animal species, known as troglobionts, mostly have elongated legs and palps. Low metabolisms and stable living conditions enable very slow reproduction and greatly extended life spans. Troglophiles are those species which can also be found above ground or migrate between the two habitats (either on a daily or seasonal basis).
Given the living conditions, subterranean fauna is much poorer than that above ground. With the exception of troglophile species, such as bats that feed outside and only rest in the caves, all land cave animals are tiny, rarely reaching the length of one centimetre.
Beetles (Coleoptera) are the most numerous, such as the Carabidae, Anophthalmus spp., Leptodirus hochenwartii and other, even tinier relatives. Many species in the underground belong to the orders Araneae (spiders) and Pseudoscorpionida (pseudoscorpions), while the snow-white Titanethes albus is one of the most commonly seen troglobionts.
The situation in underground waters is similar, the only exception being that troglobionts are here represented by the "giant" cave salamander (Proteus anguinus) that can exceed 20 centimetres in length. Otherwise, various kinds of crustaceans prevail in the waters, both in terms of species number and distribution density. The crayfish (Astacus astacus) is only an occasional migrant, the most numerous being copepods (Copepoda), the body size of which is around a millimetre, followed by isopods (Isopoda) and amphipods (Amphipoda). Blind amphipods are the most varied group; the smallest species are only two millimetres long while those that of two millimetres or longer are comparatively quite large.
At the entrance of the Reka River into the Škocjan Caves, the water contains Oligochaeta worms, tiny Cyclops, but, above all, water larvae of numerous insects, especially mayflies and gnats. These animals supersede the real cave animals. In deposits and guano, mites are found as well as springtails, troglophile spiders and cave grasshoppers.
When filtering the rainwater at the entrance parts of the Škocjan Caves, 23 species of tiny millimetre-long copepods were found. Elaphoidella Keifer or Škocjan is known only in these parts. The Škocjan Caves are a typical habitat of further five species of copepods. The cave salamander (Proteus anguinus) has also been discovered in Mejame, which are situated precisely on the border of the regional park.
The moth Scoliopteryx libatrix can often be seen on the walls near the entrance to the caves. This moth from the Noctuidae family hides in the caves from the scorching sun and remains in the cave throughout winter months. Geometer moths or the Geometridae are also occasional inhabitants of cave entrances.
Geographical and historical conditions enabled the research of underground organisms in the Slovenian Karst in the wider Postojna area. The first scientifically described troglobiont was the cave salamander or Proteus anguinus in 1758. This was followed by the blind cave beetle (Leptodirus hochenwartii) in 1832. We now know that Slovenia boasts one of the richest land cave faunas with approximately 200 species and the richest aquatic troglobiotic fauna by far with over 200 species in the world – that is among similarly large areas. Yet a question remains: will we be able to protect this heritage?
Slapnik, Rajko, 2002: Flora in favna (Flora and Fauna), Škocjan Caves Monograph, published by the Škocjan Caves Park, pp. 78-84;
Sket, Boris 2005: Življenje v podzemlju (Life in the Underground), accompanying text in the museum collection at the Delez Homestead;
Pipan, Tanja 2005: Podzemeljska favna Škocjanskih jam (Škocjan Caves Subterranean Fauna), accompanying text in the museum collection at the Delez Homestead.