Pivka intermittent lakes as a hot spot of biodiversity in Slovenia

The water dynamics of the Pivka lakes are reflected in various ways, and this is reflected in the great biodiversity. We find an exceptional diversity of flora and fauna here due to the intertwining of the water game, the man who cultivates extensive use of meadows and pastures, and the sub-Mediterranean location. We find special ones in a variety of habitats (habitat types), such as wet and dry meadows, shrubs, forests, and karst caves.

The small fairy shrimp (Chirocephalus croaticus), which is endemic to Petelinjsko jezero Lake and its surroundings, should not be overlooked. Another unique species is the olm or proteus, which lives in the Pivka region’s underground (Proteus anguinus).

On the surface, tadpoles and aquatic insects are mostly found in wet meadows during floods, whereas fragrant flowers, colourful butterflies, and birds thrive during the dry season…

Fish would be expected in the lakes, but there are none due to dry periods, particularly during the summer, when the water hides underground.

Herbs thrive in dry karst meadows, which are also useful in home cooking. Many birds, including the rare Barred warbler, fieldfare, and Red-backed shrike, are secretly watching us in the bushes, which are densely forested with thorns of blackthorn, rosehip, hawthorn, and juniper.

Along the lakes are Javorniki forests, which are home to interesting animals such as deer, roe deer, lynx, wolf, and bear. We must not forget the squirrel that greets us along a footpath or the field hare that runs across the path after we have wandered around the landscape.

Meadows of Pivka intermittent lakes and their use

Extensive wet meadows predominate in the basins of the Pivka lakes, which form lakes more frequently, and extensively cultivated meadows are partially represented, whereas only extensively cultivated meadows are present in the basins that form lakes less frequently. In the hollows, which rarely form lakes, there are extensive dry and semi-dry karst grasslands. These are normally found on the slopes of lake basins.

In general, the central parts of the bottom of the Pivka Lake basins have thicker soil, whereas the marginal parts of the bottom have thin soil, and the hollows of Palško and Petelinjsko jezero Lakes have even rocky soil. “Jamči” have been preserved among the fallow lands at the bottom of the lake basins where fields were once cultivated. Fallows (abandoned, grass-covered fields) are typical of basins that are less frequently lake-like, whereas basins that are more frequently lake-like have no fallow lands or are limited to higher, marginal parts of the bottom and higher lying side basins.

The smaller basins of the Pivka lakes are better maintained; their bottoms are completely mowed, and there are no overgrown areas at the bottom (the exception is Kalsko jezero Lake). Plots are typically mowed in June, whereas some lakes are mowed no earlier than in August. Petelinjsko jezero Lakes has the highest proportion of unmown areas, where the Mouse garlic plant predominates, giving cow’s milk a distinct smell and taste, making the lake’s feed preferred for horses. The majority of pastures have been relocated to the slopes of lake basins.

What threatens the meadows of Pivka lakes?

The main threat to the preservation of nature-important meadows at the bottom of some Pivka lakes basins, namely the Palško jezero, Petelinjsko jezero, Veliko Drskovško jezero, and Kalsko jezero lakes, is overgrowth. In addition to water retention and shallow and rocky soils, the icing of lakes in winter can cause the branches of bushes and trees to break, inhibiting overgrowth. Meadow fertilisation is much less prevalent than overgrowth. Rooted-up meadows indicate the presence of wild pigs.

The driving of motor vehicles off the beaten path endangers the Pivka lakes as well. Driving a motor vehicle on the soaked ground causes damage to the turf.

Habitat types

The term habitat type can be interpreted in a variety of ways. We find several different words for the same concept in our and foreign contributions with nature conservation content – living environment, habitat type, habitat, biotope, ecotype. The authors’ goal is always the same: to bring a wider audience closer to the recognisable living environments in nature that we have been following since childhood.

A plant or animal community as a distinctive living part of an ecosystem associated with inanimate factors (soil, climate, presence and quality of water, light, etc.) in a spatially defined area is referred to as a habitat type.

According to Article 31 of the Nature Conservation Act (Official Gazette of the Republic of Slovenia, No. 96/04 – official consolidated text, 61/06 – ZDru-1, 8/10 – ZSKZ-B, 46/14, 21/18 – ZNOrg, 31/18 and 82/20) a habitat type is defined as a biotope or biotically distinct and spatially complete unit of an ecosystem.

Individual habitat types can be distinguished from the environment even by a non-expert who observes nature with keen interest. At a young age, everyone learns to distinguish the forest from the grassland and the rocks from the water while getting to know their surroundings. These are examples of habitat types of the highest hierarchical level. A more detailed division of habitat types is intended primarily for experienced professionals and largely corresponds with the type of vegetation (individual plant communities or groups of communities).

The following sections describe five habitat types found in the Seasonal Lakes of Pivka Nature Park.

The presence of 17 intermittent lakes distinguishes the Pivka Valley area. Intermittent lakes are a rare habitat type because they are associated with areas with karst phenomena. They are only found in Ireland and southern Europe, from Slovenia to Montenegro, in the Dinaric-Karst regions. They are mostly found on the Balkan Peninsula in the form of large karst fields, which are now home to extensive agricultural areas. Intermittent lakes occur in Slovenia’s Dinaric and pre-Dinaric areas, including the Pivka lakes, Lake Cerknica, Planinsko and Radensko polje, and Ponikva pod Krimom.

Intermittent lakes are filled with water for one to six months, usually from autumn to spring, and then drain away in the spring. In the case of heavier rainfall, they can also be filled for a shorter period of time in the summer. The duration of lake formation is also affected by microrelief and the method of lake filling (surface watercourses and groundwater).

The water is nutrient-rich and usually a few metres deep, allowing light to penetrate to the ground and thus allowing the development of terrestrial vegetation to begin in the spring, under water.

Special plant communities have developed on the grasslands of the lake basins as a result of the unique flood dynamics. Because vastly different plant groups thrive in these ecological conditions, this habitat type contains a diverse range of communities.

Intermittent lakes are primarily threatened by interventions in area hydrological regimes (digging ditches, draining, diverting water, filling up depressions, etc.), polluted surface and groundwater, increased uncontrolled tourist and recreational visits, and changes in agricultural use, ranging from abandonment to intensification.

The endangerment factors in the Pivka intermittent lakes area are agricultural abandonment on the one hand and agricultural intensification on the other.

Intermittent lake areas are also covered by a variety of habitat types, including meadows with dominant purple moor-grass on carbonate, peat, and clay-mud soils (Molinion caeruleae). Unfertilised meadows on moist to wet soils characterise this habitat type.

It occurs in areas where there is water stagnation due to poor permeability, proximity to watercourses, or periodic flooding. The soil is nutrient-poor and acidic, with a high proportion of organic matter or humus, and contact with the parent geological base is broken.

The aforementioned habitat type can be found all over Slovenia. It can be found on stream alluvium, the bottoms of larger and smaller valleys, plains, basins, and floodplains, as well as in the Pivka Valley.

Purple moor-grass is one of the most rapidly disappearing habitat types, as it is threatened by a variety of factors. These are primarily different interventions in the existing hydrological regime of (micro) areas that affect the presence of water in the soil (digging ditches, draining, diverting water, filling up depressions and the like). Changes in agricultural use, particularly premature mowing, have a significant negative impact on this habitat type, preventing plant seeding. To improve grasslands, these areas are fertilised, and in some cases, adding lime occurs is used, which affects growing conditions and reduces the diversity of grassland species composition.

The greatest threat factor in the area of the Pivka intermittent lakes is the abandonment of agriculture and the resulting overgrowth of grasslands with woody overgrowth.

The dry and semi-dry grasslands of the Western Balkans are represented by a strip of deciduous sub-Mediterranean forests of beech, black hornbeam, downy mildew, and karst hornbeam along the eastern Adriatic coast from the Trieste Karst to Montenegro. They were formed by human activity (deforestation and mowing) and animal activity (grazing), and some date back to 2500 years.

They grow in the natural habitats of beech and oak forests, particularly on limestone, dolomite, and flysch. The soils on the sites vary greatly – low to medium in nutrients, basic to slightly acidic, and dry to moderately moist – but such grasslands are always the result of extensive use. These habitats were also managed differently depending on their typology. Grasslands, which developed on slightly deeper soils and thus contain more nutrients and are moister, were managed in the same way that meadows were – by mowing. Grasslands on shallow, rocky soils, frequently exposed to bora winds, were managed as pastures. Both have certain ecological and biogeographical similarities, with their plant communities differing from one another. Plants are light-loving and do not tolerate fertilisation, which is common among the communities that inhabit these grasslands.

In Slovenia, they predominate in the sub-Mediterranean area. This type used to predominate there, but it now accounts for only 1 to 5% of the surface.

It is threatened by the cessation of agricultural use (mowing and grazing) and the resulting overgrowth of wood overgrowth, as well as fertilisation. This habitat type is stable in areas where overgrowth is slowed by wind and/or rock. Overgrowth is also slower at higher altitudes. With the abandonment of grazing, particularly the disappearance of transhumance (a type of grazing in which herds of small ruminants with shepherds moved to areas with more vegetation) in Slovenia, this habitat type is prone to an overgrowth in large areas. The overgrowth is not noticeable at first, but the habitat quickly transforms into a bush and pioneer forest. Infrastructure interventions (wind farms), land consolidation, and off-road driving all have negative consequences in this area as well.

The biggest risk factors in the Pivka intermittent lakes area are changes in agricultural use – on the one hand, pasture abandonment, and on the other hand, pasture intensification, as there is significantly more livestock on pastures than their capacity. Additional stressors include the conversion of meadows to pastures as a result of the free-range implementation, as well as uncontrolled tourist visits to the area.

Illyrian beech forests thrive on a carbonate base at an altitude of 600 to 1400 m. They consist of several different communities (Dinaric foothill beech forests, beech forests with fir, high mountain beech forests), which are characterised by greater species diversity than other beech forests.

Illyrian beech forests predominate in the Dinaric world of Slovenia, where they are also the best preserved. They also reach the Alps and the eastern parts of Slovenia (Orlica, Bohor, Kum, Boč, and Donačka Gora).

In the past, they were threatened by coppice forest management, collecting litter as bedding for animals, and forest grazing, but now they are threatened by spruce promotion and difficult rejuvenation due to gnawing.

The threat to this habitat type in the Seasonal Lakes of Pivka Nature Park is posed by difficult rejuvenation due to damage, particularly fir, and climate change.

These are caves and associated water bodies that are not accessible to the general public and are home to specialised or endemic animal species. These include a variety of invertebrates, particularly beetles, crustaceans, and molluscs, which have very limited distribution. Many species of bats hibernate and breed in the caves, which also serve as a habitat for olm.

The majority of caves in Slovenia are found in the Dinaric world.

They are threatened by water pollution, tourist overcrowding, and, in some cases, waste disposal.

The habitat in the Pivka intermittent lakes area is threatened primarily by old landfills and the resulting polluted water, which then flows through the area, both underground and above ground.

Endemics in the Pivka region

  1. Fairy shrimp (Chirocephalus croaticus)

When the researchers inventoried the aquatic fauna in the Pivka intermittent lakes, they discovered that it is not particularly diverse, but it contains a number of interesting species. At least three of the crustaceans found in the Pivka lakes area are endemic, and two species have their only locality in Slovenia here. Petelinjsko jezero Lake is critical for the survival of a 12–15 mm crustacean known as the Karst Fairy shrimp (Chirocephalus croaticus). The shrimp was discovered in puddles in Croatia’s Neretva River’s lower reaches, but it could no longer be found there. They later discovered it in two more puddles near Lake Cerknica, but because they buried the area, they also destroyed the fairy shrimp’s environment. They are currently only found in Petelinjsko jezero Lake and Jeredovce Lake. The species can be found in large numbers under favourable conditions. This Petelinjsko jezero Lake and Jeredovce Lake resident is endemic, which means that this species of shrimp can only be found in the Pivka intermittent lakes area in the entire world.

  1.  Olm (Proteus anguinus)

This area is also important for the olm (Proteus anguinus), which lives in the Dinaric-Karst groundwater from the Soča river basin in Trieste to the river Trebišnica in Herzegovina, earning it the name endemic to the Balkans. It is Europe’s sole representative of cave vertebrates.

The species is listed as vulnerable on the Red List of endangered amphibian species and is also protected by the Natura 2000 network.

Plant and animal species

We go over specific plant and animal species from the Nature Park area in greater detail.

Birds

The warbler family (Sylviidae) includes several genera of songbirds that live in bushes and trees. They are smaller birds, up to the size of a sparrow, with inconspicuous colouration and almost no sex differences. They eat insects, hide frequently, and rarely land on the ground. In addition to Barred warblers, this family also includes leaf warblers, reed warblers, tree warblers and grass warblers.

The Barred warbler is grey, with striped throat, belly, and tail feathers that are especially noticeable in males. A mosaic agricultural landscape with tree-shrub borders and overgrown areas represents the bird’s habitat, which is slightly larger than that of the domestic sparrow (15–17 cm). The female builds her nest in smaller trees, shrubs or blackberries. She prefers thorny shrubs such as hawthorn, rosehip, barberries, blackthorn and blackberries. Her territories often overlap with the territory of the Red-backed shrike. They often work together to protect nests, and they may even nest in the same bush at times. Invertebrates, as well as various berries and soft fruits, provide food for the Barred warbler in late summer and autumn.

It is a migratory bird that spends the winter in East Africa before returning to nesting grounds in May.
It nests in Slovenia’s lowlands with a mosaic agricultural landscape, where it lives in areas with bush-tree borders, bushes, and meadows. It lives in both wet and dry meadows in the Pivka region, which are overgrown with thermophilic shrubs here and there.

The species is listed as vulnerable on the Red List of endangered nesting bird species and is also protected by the Natura 2000 network.

It is threatened by agricultural abandonment and the resulting overgrowth of the mosaic landscape into shrublands and pioneer forests that are unsuitable for the species, as well as agricultural intensification, which is reflected in the disappearance of tree-shrub borders, expanding fields, and the like.
The same factors that endanger the Barred warbler apply to the Pivka intermittent lakes area.

The shrike family (Laniidae) is distinguished by a powerful beak with a curved tip and a long tail. Shrikes are fantastic songbirds that behave similarly to birds of prey in that they wait for their prey from a high perch, preferably on freshly mowed grass or macadam roads. If they have too much food, they will stick it on thorns, broken branches, or forked branches. Most European representatives are migrants.

The male Red-backed shrike has a grey head, a black eye mask, a brown back, and a pink chest and abdomen, whereas the female has a brown-grey body with streaks on the hips and abdomen. A mosaic agricultural landscape with tree-shrub borders, bushes, and mowed meadows is the habitat for a bird slightly smaller than a common blackbird (16–18 cm). Females build their nests in thorny shrubs like rosehip, blackthorn, hawthorn, and blackberry. They feed on insects (especially beetles), small mammals, birds and reptiles.

The Red-backed shrike is a migratory bird that spends the winter in East and South Africa before returning in April.
In Slovenia, it lives in a mosaic agricultural landscape with mowed meadows, individual shrubs, and borders, which it uses for nesting and as a perch.

It is still a common nesting bird in Slovenia, with the highest densities in the Pivka region, the western part of the Posavje hills, Bela Krajina, Sotelsko and Voglajnsko hills, and Slovenske Gorice, whereas its numbers in Europe have plummeted due to agricultural intensification (Great Britain).

The species is listed as vulnerable on the Red List of endangered nesting bird species and is also protected by the Natura 2000 network.

The Red-backed shrike is threatened by agricultural intensification, specifically, the expansion of arable land at the expense of meadows, the disappearance of borders and bushes on the one hand, and agricultural abandonment on the other, resulting in an overgrowth of shrubs and pioneer forest in the mosaic landscape.

The risk factors for Red-backed shrike described above also apply to the Pivka intermittent lakes area.

Nightjars (Caprimulgidae) are insect hunters who are active in the evenings and at night. They have a long tail and long and narrow wings, while their legs and beak are short. During the day, they sit motionless on the ground or longitudinally on branches, where the protective colour of their feathers makes them difficult to notice (in the colour of the bark).

The European Nightjar is a striped bird with a sandy and deep brown beak and an extremely wide mouth. During mating season, they make a buzzing sound at night that sounds like a small engine from a distance. The bird, which is about the size of a common blackbird (24 – 28 cm), lives in a dry, semi-open landscape with few trees (such as pine trees), on sunny forest edges, oak bushes, and clearings in the deciduous forest. The female builds her nest on the ground, in the open, or under the cover of shrubs. Insects, particularly moths and beetles, are the primary food of the European Nightjar, which hunts exclusively by sight in flight.

The European Nightjar is a migratory bird that spends the winter in Africa before returning to nesting grounds in April and May.

Vrsta je uvrščena na Rdeči seznam ogroženih vrst ptičev gnezdilcev kot prizadeta vrsta ter varovana tudi preko omrežja Nature 2000.

In our country, the European Nightjar is most common in southwestern Slovenia, but it can also be found elsewhere. It is commonly found in the Pivka region and the northern part of the Reka river valley in the Notranjska region. It prefers to inhabit overgrown agricultural land, coniferous forests, and extensive meadows in the Pivka region, avoiding fields and intensive meadows.

The species is listed as an affected species on the Red List of Endangered Species of Nesting Birds and is also protected under the Natura 2000 network.

It is primarily threatened by food shortages caused by pesticide use, as well as the disappearance of suitable nesting habitats (thermophilic forests, juniper shrubs, and dry grasslands), which also applies to the Pivka intermittent lakes area.

In our country, the Euroasian hoopoe (Upupidae) is the only representative of the hoopoe family. It is easily identified by its large, upright tuft, thin and curved beak, and highly visible black and white wings in flight. On the ground, however, it is surprisingly unobtrusive while looking for food.

It gets its name from the stench of their young’s secretions, which repel predators. It makes a gentle “hup-hup-hup” sound, hence the common name “hoopoe”. The bird, which is slightly larger than a common blackbird (25–29 cm), lives in a warm, mosaic agricultural landscape with many stalks (trees, bushes, and piles of stones), extensive meadows, and meadow orchards. It builds its nest in hollowed trees, frequently in old meadow orchards or willows. It forages for large insects, their larvae, and beetles in mowed meadows, grassy farmyards, cart tracks, road edges, pastures, and occasionally manures or around grazing animal excrement.

It is a migratory bird that spends the winter in Africa and the Mediterranean south of the Sahara and returns to nesting areas in April.
The Eurasian Hoopoe can be found in Slovenia’s Karst, Vipava Valley, and Pivka. It lives in a mosaic agricultural landscape.
The species is listed as an affected species on the Red List of Endangered Species of Nesting Birds and is also protected under the Natura 2000 network.

It is threatened by the disappearance of meadows as a result of conversion to fields or overgrowth, the disappearance of meadow orchards, urbanisation and related changes in house landscaping, and possibly the use of anti-European mole cricket toxins, which can be lethal to birds. It has declined dramatically in Europe as a result of agricultural intensification (lack of suitable nesting sites and food), and in some places has even disappeared.

The bird is endangered in the Pivka intermittent lakes area, primarily because of overgrown areas that have turned into bushes and pioneer forests, which do not suit the species.

Owls (Strigidae) are predators that are active primarily in the evening and at night. They have a large head with large, forward-pointing eyes, a downwardly curved beak, and soft feathers that allow them to fly almost silently. Owls do not build their own nests, but instead lay their eggs in tree hollows, nests built by other birds, or on the ground.

The Eurasian scops owl is a small owl, smaller in size than a common blackbird (19-21 cm) and is best known for its monotonously repetitive “tjü” sound. While avoiding fields and dense forest, it inhabits a mosaic agricultural landscape with borders, meadow orchards, extensive meadows, fallow land, and abandoned vineyards. It can also be found in urban areas, city parks, and tree-lined avenues.

It nests in Slovenia in extensive orchards, tree borders, and holes in stone houses and rocky walls. It primarily feeds on large insects (beetles, moths, and Orthopteroidea like grasshoppers) and vomits indigestible food debris. We can tell which species they belong to, based on their vomit, specifically their size, shape, and colour.

It is Europe’s only true migratory owl, spending the winter in Africa and returning to us in early April.
The Eurasian scops owl is most common in Slovenia’s southwestern region, specifically the Karst, the Koper hills, Pivka, the southwestern part of Javorniki and Snežnik, and Banjšice massif.

The species is listed as an affected species on the Red List of Endangered Species of Nesting Birds and is also protected under the Natura 2000 network.

It is threatened by the disappearance of meadows as a result of conversion to fields or overgrown forest, the decay and disappearance of meadow orchards, urbanisation and related changes in house landscaping, and the use of poisons against European mole cricket and snails, which can be harmful to birds.

The bird is endangered in the Pivka intermittent lakes area, primarily due to agricultural intensification and a lack of suitable nesting areas.

Butterflies

The Scarce large blue is a representative of the butterfly in the family Lycaenidae. It is a diurnal butterfly with a wingspan ranging from 33 to 37 mm.

This species, like other large blues, has a complex life cycle and specific requirements, such as moist extensive meadows with Great burnet (Sanguisorba offincinalis) and anthills of the genus Myrmica. When the Great burnet’s flowers are not fully developed, the female lays one egg in the flower head. The caterpillars first feed on developing seeds, then after 3 to 4 weeks (with less than 10% of their final weight), they fall to the ground and await the worker ants of the main host species, Myrmica scabrinodis. Or other species of ants from the same genus. Many of them are killed by predators at this stage. The ant worker recognises the caterpillar as “one of its own” and brings it to the anthill, where it becomes a predator of the ant brood. In the summer, the caterpillar burrows into the anthill and matures into an adult butterfly, which the host ants no longer recognize “as their own,” so it may become their prey as it crawls out of the anthill. It has one generation per year.

In Notranjska and Primorska regions, the species is found distinctly locally.
The Scarce large blue butterfly is listed as a vulnerable species on the Red List of endangered butterfly species and is also protected by the Natura 2000 network.

The species is primarily threatened by habitat destruction caused by agricultural intensification (drainage, liming, fertilisation, mowing of meadows at inappropriate times), changes in meadow use and overgrowth, water management measures, construction of transportation and municipal infrastructure, and urbanisation.

This species of diurnal butterfly is endangered in the Pivka intermittent lakes area, primarily due to the intensification of agriculture on wet meadows and the simultaneous mowing of larger areas.

The Large copper is the largest European representative of the Lycaeninae family. It is a type of diurnal butterfly with a wingspan of 40 mm.

Lowland wetlands and floodplains, reeds, meadows, and sedges, river and lake banks, high and dense herbaceous vegetation, water ditches, gravel pits and clay pits, and abandoned and overgrown gravel pits are the species’ habitats. The female lays her eggs in small clusters on the underside of the leaves of various dock plants. It has two generations per year, with the second generation of caterpillars overwintering and hatching on the stem or along the central vein of the food plant in the spring. Adult butterflies feed on nectar, primarily from purple and yellow flowers of various plant species.

In Notranjska and Primorska regions, the species is extremely rare.
The Large copper butterfly is listed as vulnerable on the Red List of endangered butterfly species and is also protected by the Natura 2000 network.

Hydromelioration (drainage of wetlands, arches, floodplains, and wet meadows, extensive flooding of river areas), agromelioration (filling up water ditches, depressions), intensification of agricultural use of meadows (fertilisation and excessive mowing), and urbanisation are the most significant threats to the species.

The greatest threat to this species of butterfly in the area of the Pivka intermittent lakes is posed by changes in agricultural use – fertilisation and more frequent mowing of meadows.

The Marsh fritillary is a representative of the Nymphalidae family. It is a type of diurnal butterfly with a wingspan of 30 to 46 mm. It is a highly variable butterfly species with geographical and ecological diversity.
It requires moist to semi-dry and warm species-rich meadows and shrubs, forest edges, and water banks from the lowlands to the highlands in order to survive.

In Slovenia, it is represented by three types of populations. Caterpillars feed primarily on devil’s-bit scabious in wet meadows, small scabious in dry meadows, and various species of Gentiana plants in the highlands. Caterpillars feed and overwinter in groups in a silk net that surrounds the plant’s lower part. Adult butterflies feed on honey plants in extensive meadows and shrubs near forest edges and riverbanks.
The species is common in the Notranjska and Primorska meadows.

The Marsh fritillary is listed as vulnerable on the Red List of endangered butterfly species and is also protected by the Natura 2000 network.

It is threatened by the abandonment of extensive agriculture and meadow overgrowth. Hydromelioration interventions endanger wet meadow populations, and infrastructure construction, particularly highway construction, endangers some populations.

The main threat to this species of diurnal butterfly in the Pivka intermittent lakes area is the abandonment of agricultural use and the subsequent overgrowth of agricultural land. This, in addition to reducing living space, causes it to divide into smaller parts, which has an additional negative impact on this poorly mobile butterfly species.

Amphibians

The Italian crested newt is the largest type of newt in Europe. It can grow up to 25 cm and on average reaches about 18 cm.
On the back of the male, there is a saw-toothed ridge, and on the back of the female, there is a bright yellow line. The larvae are similar to the parents but differ in that they have external gills, tying them to water life. The adult animal feeds on land, primarily on the vast moist meadows of hilly terrains. It can spend the winter on land (in forests or shrubs, in damp places under rocks, in rock crevices and holes, under or in decaying wood…) or in water, where it also reproduces (medium-sized ponds and other still waters that very rarely dry out and have lush riparian and aquatic vegetation and clear water).

The occurrence of the species in the Pivka intermittent lakes area is estimated solely on the basis of habitat assessment and ecological requirements; no actual inventories of the species are conducted. The species is listed as vulnerable on the Red List of endangered amphibian species and is also protected by the Natura 2000 network.

The destruction and pollution of aquatic environments, fish introduction, intensive agriculture, and roads and traffic all pose threats to the species. Ecological corridors that connect living areas into a functional whole are critical for species conservation.
The main threats in the Pivka intermittent lakes area are overgrowth and abandonment of the use of ponds, puddles, and other artificial water surfaces, resulting in the disappearance of suitable spawning sites. The introduction of fish, particularly aquarium fish, in permanent water surfaces adds to the pressure.

Bats

The Lesser horseshoe bat is the smallest member of the horseshoe bat family (Rhinolophidae), and it gets its name from the unusual skin formation around the nostrils that resembles a horseshoe.

The bat is 4 to 5 cm long and measures 19–25 cm across the wing. As with other horseshoe bats, the ears are large and pointed. The coat is fine and silky, greyish brown on the back and slightly lighter on the belly in adults, and completely grey in young. During the winter hibernation, they completely wrap themselves in the wing membrane, which is thin and dark. It prefers warm leeward valleys with deciduous trees and shrubs, as well as karstic areas with karst caves. It feeds on insects, primarily moths, net-winged insects, and caddisflies. It hunts low, just a few feet above the ground, in slow flight and circling. It hunts for prey primarily in the forest or on the forest’s edge, as well as along borders/hedgerows and riparian vegetation, and less frequently above open water and pastures. During the day, it seeks refuge in the attics of buildings, where they form maternity colonies.

The Lesser horseshoe bat is a common species in Slovenia, with the exception of the lowlands of Styria and Prekmurje.

The presence of the species was discovered in individual sacral buildings and caves in the Pivka intermittent lakes area. Unfortunately, no regular bat inventories are conducted in this area, so much about these bats remains unknown.

The Lesser horseshoe bat is listed as an endangered species on the Red List of Endangered Mammal Species and is also protected under the Natura 2000 network.

The main threats to this species of bat are the maternity colonies being exposed to human intervention – vandalism, the inappropriate timing and implementation of building renovations, church illumination and preventing bats from accessing daily shelters. During the winter, the species is vulnerable to vandalism or disturbances caused by cave visitors ( disturbance of animals during hibernation, light, noise, smoke…).

Large carnivores

The Pivka intermittent lakes area is important for large carnivores due to the presence of large, closed forests. For all three large carnivores – wolf (Canis lupus), bear (Ursus arctos), and lynx (Lynx lynx) – Javorniki are especially important as part of the Snežnik-Javornik massif in connection with the Kočevje forests and the Gorski Kotar forests. They form the largest compact sparsely populated forest complex, which serves as the primary habitat for large carnivores. The jackal is also increasingly present in the area (Canis aureus).

Wolves and bears, in particular, are frequently seen on the lakes, and the wildcat is also present at all times (Felis silvestris).

The significance of large carnivores in nature
Large carnivores are predators that play an important role in regulating ungulate density, as well as the overall functioning of natural ecosystems. Some of them are also scavengers (especially bears), thus performing a sanitary role in the ecosystem. Because some species (such as bears) eat plant fruits, they aid in seed dispersal, increasing the vegetation structure and diversity of the ecosystems in which they live.

The wolf is the largest member of the dog family (Canidae), which grows up to 140 cm and weighs up to 70 kg. During the day, they hide in dense undergrowth or inaccessible areas. It is primarily a nocturnal predator that gathers in herds. Group hunting allows it to tackle larger animals as well. Prey is usually exhausted in a tiring chase during hunting expeditions that can last hundreds of kilometres. It feeds mainly on deer, elk and wild boars. It mainly hunts animals that are in poor physical condition, so it plays an important role in the ecosystem. It is very adaptable, with only human activity, particularly the high density of settlements and roads, limiting it.

Humans have always persecuted it for attacks on small ruminants, which are more likely in the absence of their food, particularly ungulates. Despite its bad reputation, it is not dangerous to humans.

The preservation of continuous forest stands and the connection of populations with corridors are critical for the species’ survival.
The wolf is listed as an endangered species on the Red List of Endangered Mammal Species and is also protected under the Natura 2000 network.

The lynx is a member of the cat family (Felidae), and it is distinguished by long hairs on the tips of its ears. It weighs from 16 up to 34 kg. The lynx is a solitary species that only associates with other members of its species during mating. It is a specialised predator that hunts its prey from ambush. Small ungulates (deer, chamois) are their most common prey, but they can also feed on elk, wild boar, badgers, rabbits, wild cats, and hazel grouse. Its habitat is a forest, which can be interrupted by agricultural land.

An adequate amount of prey and human tolerance is critical for survival. The lynx is a timid animal and harmless to humans. The wolf is its main competitor in areas where the proportion of small ungulates is low. It is necessary to establish a link between isolated populations in Europe in order to preserve it.

The lynx is listed as an endangered species on the Red List of Endangered Mammal Species and is also protected under the Natura 2000 network.

The brown bear is a representative of large carnivores from the bear family (Ursidae). It has a strong body that measures 150 to 250 cm in length and a short tail. It is a solitary animal that can live up to 35 years. The central habitat of bears in our country is the beech-fir forests of the Dinaric high karst. The bear is predominantly (90%) a herbivorous animal that feeds on forest fruits and seeds (beech, oak, chestnut, hazel, walnut, dogwood, rowanberry, raspberry, strawberry… ), grass, and mushrooms, as well as ants, carrion, and herbivorous offspring. Because of its size and a primarily plant-based diet, which is low in energy, the bear must consume large amounts of food, which necessitates a lengthy search, resulting in long distances. It sleeps during the winter months, but this is not true hibernation. The den, which should not be exposed, is critical for the selection of living space, especially for females who give birth to young in the winter. The early stages of the forest, where fruit-bearing plant species thrive, are also critical to its habitat.

The bear is listed as an endangered species on the Red List of Endangered Mammal Species and is also protected under the Natura 2000 network.

Plants

The most common cause of plant endangerment is habitat change, but some plants can also be endangered by overharvesting, digging, uprooting. As a result, certain plant species are protected by special regulations. However, we should rather admire plant species in their natural habitat and only take photographs of them.

Representatives of wet meadows

The Solitary virgin’s-bower is a plant from the buttercup family (Ranunculaceae). It is a flowering plant of rocky bushy slopes with an upright and non-woody stem that blooms from June to August. It is one of the two uncommon Leather Flower’s representatives, as the others are wooden climbers. The Solitary virgin’s-bower is a plant that grows up to 25 cm tall, has ovate to linear leaves that are never divided, and purple flowers. These are usually arranged individually, rarely in groups of two or three.

It is a rather rare plant in Slovenia, inhabiting moist meadows and occurring in the sub-Mediterranean, sub-Pannonian, and pre-Alpine areas, with the majority of finds being in the Notranjska region.

The species is quite common in the meadows of lake basins in the Pivka intermittent lakes area.

The Wild gladiolus is a plant of the iris family (Iridaceae). It is 30 to 50 cm high. The double row inflorescence, which can be observed from May to June, bears 3 to 20 purple bilaterally symmetrical flowers. The plant got its genus name from the shape of the leaves, reminiscent of a sword.

The species is found in Slovenia on moist and dry meadows ranging from the lowlands to the Montane zone of the Alpine, pre-Alpine, Dinaric, Pannonian, and sub-Mediterranean regions. It is most common in the Notranjska region and the Karst.

The Wild gladiolus is listed on the Red List of Threatened Plant Species as a vulnerable species. It is also protected in Slovenia and thus cannot be collected, damaged, or transferred from its natural habitats.

The species is found in the Pivka intermittent lakes area on wet meadows of lake basins as well as dry, stony karst grasslands.

The Mouse garlic is a plant from the onion plant family (Alliaceae), which reaches 20 to 60 cm. Its upright stem is characterised by a sharp triangular shape. The linear leaves are more or less ground-based and have a strong garlic aroma. Elongated bulbs attached to a short rhizome are hidden in the soil. From July to September, numerous stalked pink flowers are grouped into hemispherical inflorescences that lie terminally at the end of the shoot.

The species is found in Slovenia on moist meadows ranging from the lowlands to the subalpine belts of the pre-Alpine, pre-Dinaric, Pannonian, and sub-Mediterranean areas.

The Mouse garlic is listed as a vulnerable species on the Red List of Threatened Plant Species.

In the area of the Pivka intermittent lakes, the species is present mainly on the wet meadows of lake basins.

The Great Burnet is a plant in the rose family (Rosaceae) that grows to be from 30 cm to 1 m tall. It is distinguished by dark purple-headed inflorescences with many four-petaled flowers that bloom from May to September. The leaves are bare, odd-pinnate, with a serrated edge.

The plant grows on moist meadows and swamps throughout Slovenia, from the lowlands to the Montane zone. It is a food plant for the Scarce large blue butterfly, whose females lay eggs on it.

The species is found primarily on the wet meadows of the lake basins in the Pivka intermittent lakes area, and it is mostly found along the bed of the Pivka river near the village of Klenik.

The Siberian Iris is a plant of the iris family (Iridaceae) that grows to a height of 30 to 50 cm. Two blue flowers, whitish on the inside with pronounced blue veins, usually develop at the top of the round, hollow stems. Irises bloom from May to June. The scientific name of the genus is derived from the name of the ancient Greek goddess of the rainbow, Iris, while the flower’s Slavic name is derived from the name of the Slavic god, Perun.

It grows on marshy meadows throughout Slovenia, from the lowlands to the Montane zone.

The Siberian Iris is on the Red List of Threatened Plant Species, specifically in the category of vulnerable species. The species is also protected in Slovenia, where intentional destruction, particularly plucking, cutting, pulling, and taking from the wild, is prohibited.

In the area of the Pivka intermittent lakes, the species is present mainly on the wet meadows of lake basins. This is the habitat of the subspecies Siberian Iris subsp. sibirica, which is a wetlands representative.

The Marsh gentian is a plant of the gentians family (Gentianaceae), which grows from 15 to 50 cm. The flowers, which appear from July to September, are five-petaled and condensed at the top of the stem. The linear-lanceolate leaves are single-veined and oppositely arranged. It is a food plant for the Alcon blue butterfly, whose females lay eggs on it.

It grows throughout Slovenia on moist meadows, marshes, and heaths from the lowlands to the Montane zone. It is also protected in Slovenia and thus cannot be collected, damaged, or transferred from its natural habitats.

In the area of the Pivka intermittent lakes, the species is present mainly on the wet meadows of lake basins.

Representatives of dry grasslands

Dianthus sanguineus is a plant of the carnation family (Caryophyllaceae), which grows from 20 to 50 cm. It is characterised by multi-flowered head inflorescences that appear from June to August. The petals are typically blood red.
In Slovenia, the species is found scattered on dry karst meadows from the lowlands to the submontane belt of the Dinaric, pre-Dinaric and sub-Mediterranean areas. The species is also protected in Slovenia, where intentional destruction, particularly plucking, cutting, pulling, and taking from the wild, is prohibited.
In the area of the Pivka intermittent lakes, the species is present on dry grasslands.

The Fly Orchid is a plant from the orchid family (Orchidaceae). It is a slender orchid that grows to be 15 to 40 cm tall, with a ground leaf rosette and only scaly leaves on the stem. The terminal inflorescence is rarely formed by more than five flowers, and a single flower is six-petaled. Flowers of the plants from genus Ophrys, with their hairiness, odour, and shape, resemble the females of some Hymenopteran species. They attract the males of these insects, who want to mate with the flowers and pollinate them in this way.

The species is found in Slovenia on rocky slopes, sunny road cuts, barren dry meadows, and bright thermophilic forests. The Fly Orchid is listed as a vulnerable species on the Red List of Threatened Plant Species. The species is also protected in Slovenia, where intentional destruction, particularly plucking, cutting, pulling, and taking from the wild, is prohibited.

In the area of the Pivka intermittent lakes, the species is present on dry grasslands.

The Military Orchid is a plant from the orchid family (Orchidaceae) that grows between 20 and 50 cm tall and has light green ground leaves that form a rosette. With the exception of the honey lip, all petals form a helmet, giving this species its Slovenian name.

From the lowlands to the Montane zone, the species can be found scattered on barren semi-dry meadows, light forests, and forest edges in Slovenia. The Military Orchid is listed as a vulnerable species on the Red List of Threatened Plant Species. The species is also protected in Slovenia, where intentional destruction, particularly plucking, cutting, pulling, and taking from the wild, is prohibited.

In the area of the Pivka intermittent lakes, the species is present on dry grasslands.

It thrives on dry karst meadows in the Alpine, pre-Alpine, and sub-Mediterranean mountain zones of Slovenia. It is listed as an under-appreciated species on the Red List of Threatened Plant Species. The species is also protected in Slovenia, where intentional destruction, particularly plucking, cutting, pulling, and taking from the wild, is prohibited.

This Iris subspecies appears alongside the typical subspecies found on marshy meadows in the Pivka intermittent lakes Park. This is a common representative of dry grasslands, such as those found in Sveta Trojica.

The Greater Butterfly-Orchid is a plant from the orchid family (Orchidaceae) that thrives in the woods. It grows from 20 to 60 cm high and blooms from May to July. The flower’s characteristic is its extension at the back of the flowers in a form of a long greenish spike that widens slightly at the end. The scent of the Greater Butterfly-Orchid’s flowers is barely detectable.

It grows throughout Slovenia in coniferous and deciduous forests, clearings, and bushy slopes. The Greater Butterfly-Orchid is classified as a rare species on the Red List of Threatened Plant Species. The species is also protected in Slovenia, as are the orchids, where intentional destruction, particularly plucking, cutting, pulling, and taking from the wild, is prohibited.

The species is mostly found on dry grasslands and forest edges near the Pivka intermittent lakes.

The White asphodel is a plant of the Asphodelus family (Asphodelaceae), which grows to a height of 60 to 120 cm. Its tall stem is leafless and upright. All of the leaves are grooved, fleshy, and linear, and are found in a leaf rosette on the ground. From May to June, a long dense clustered inflorescence blooms at the top of the stem. The lower flowers in the inflorescence open first, followed by the top flowers. White asphodel flowers are six-petaled, with a brown central vein running down the centre of the petals. This is a plant that, according to Greek mythology, connects the world of the living with the underground world of the dead.

It grows on meadows from the lowlands to the Montane zone of the Alpine, Dinaric, pre-Alpine, and sub-Mediterranean areas in Slovenia. The White asphodel is classified as vulnerable on the Red List of Threatened Plant Species.

The species is mostly found on dry grasslands and overgrown areas near the Pivka intermittent lakes.

Sources:

Photos:

  • Alenka Mihorič
  • Bojana Fajdiga
  • Branko Česnik
  • Erika Kovačič
  • Eva Pavlovič
  • Jana Laganis
  • Marjan Krebelj
  • Martina Lužnik
  • Nina Doles
  • Peter Truskinger
  • Petra Draškovič Pelc
  • Polona Vadnjal
  • Slavko Polak
  • Tadej Kogovšek