The Škocjan Caves,
a well-known and well-explored outstanding natural
phenomenon, have long been recognized as exceptional
due to their extremely varied terrain and exceptionally
diverse flora and fauna. 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.
Alpine auricula (Primula avricula)
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.
Bats are the constant inhabitants
of the Škocjan Caves.
Subterranean life
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?
Sources:
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.
