Tag Archives: biodiversity

The island of Cres: Tramuntana

The island of Cres (Fig. 1) lies in the Kvarner Gulf, at the Croatian side of the Adriatic sea. Along with Krk, it is the largest Croatian island – both have an area of about 406 km2 . Rich in biodiversity, it hosts about 1300 plant species, many bird and reptilian species, among them various endangered and protected, of which many endemisms.

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Fig. 1 The view of the island of Cres early in the morning, seen from Tramuntana.

Tramuntana is the name given to the northern half of Cres; it is also known as the “head of the island” (or, in Latin, “Caput Insulae”). Situated just slightly above the 45th parallel, Tramuntana is widely covered by a dense forest of deciduous trees such as oaks (Quercus pubescens, Qurcus cerris), ashes, hornbeams, elks and chestnuts. Such abundance of trees is favoured by the peculiar climatic conditions, a mixture of continental and Mediterranean – known also as the submediterranean climate.

This area was once mainly used as a pasture and this activity had an important impact in the architecture of the landscape and in the creation of new components of the ecosystem with peculiar microclimates that enriched the primary biodiversity.  The inhabitants of Tramuntana practiced agriculture, raised olive trees and forest harvesting in a sustainable way, which ensured an adequate balance between plant and animal species. Sheep (Fig. 2) were important members of the ecosystem because they ensured the maintenance of the grassland in a natural way, and their carcasses were an important food source for the griffon vulture (Gyps fulvus), which inhabits the nearby cliffs. In the last few decades, the amount of sheep drastically decreased, and this led to the decrease of the number of griffon vultures in the island, since sheep are a crucial component of their food chain.

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Fig 2. In the island of Cres, sheep are free grazers. Since there are various sheep owners, they cut their ears so that they could be easily recognised. The only task of the owner is to ensure that they have enough water. During bad weather conditions, they find shelters in abandoned houses, caves or in the cavity of old trees.

In the same time, the abandonment of the practice of sheep breeding has caused many changes in the vegetation landscape, since the absence of the grazers has allowed the regrowth of the underbrush, made prevalently of Juniperus oxycedrus, Paliurus spina-christi and Crataegus monogyna.

The interior of Tramuntana is mainly covered by forests, however it is possible to see many scattered open patches with small ponds that are an important source of water for the wildlife; there are also many small areas delimited by dry walls where olive trees and old fruit trees still grow; these are excellent pastures for sheep (Fig. 3 and 4).

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What caugt my attention is the strong scent that in the whole island begins to spread starting from March, that is released by a big euphorbian species which starts to flower in this period, the Euphorbia characias subsp. Wulfenii (Fig. 5). Typical of the Mediterranean vegetation, this plant can grow up to 180 cm in height. Even though their flowers attract various insect species (Fig. 6 and 7), like all the members of the Euphorbia species, they produce a toxic white sticky sap, which has been used for treating skin excrescences since ancient times.

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Fig. 5 Euphorbia characias subsp. Wulfenii in the foreground. In the background it is possible to see the rocky coast and the spectacular cliffs. Sheep are often forced to climb the cliffs in search for food. Frequently they fall and injure themselves, and when they die, they become food for the griffon vultures.

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The following pictures (Fig. 8, 9, and 11) are just an example of the rich biodiversity of Tramuntana. Starting from early spring, a rich bird concert makes a journey in the area particulary pleasent. The forest is espeically rich in song bird species, owls, the hoopoe, the european nightjar, swifts etc. According to curren estimates, of the 136 bird species present in the island of Cres, 65 of them nest in this area. In the whole island there are 32 autochtonous amphibian and reptilian species, among them the common toad (Bufo bufo), the blue-throated keeled lizard (Algyroides nigropunctatus), the common newt (Triturus vulgaris meridionalis), the yellow-bellied toad (Bombina variegata), the agile frog (Rana dalmatina) and the slow worm (Anguis fragilis). One curios thing is that, in the island of Cres and Losinj there are no venomous snakes and still nobody knows the exact reason.

Text and photos by Ingrid Ugussi Vukman 

The twin lakes of the Lower Saxony in Germany (Die Bullenseen)

The twin lakes (Großer and Kleiner Bullenseen) are situated in the Wümme depression that was covered by ice during the Ice Age. As the ice retired, the two depressions filled with water remaind and today they are replenished by the Wümme´s branches. The small lake is since 1938 part of the nature reserve “The big and the white moor” (“Großes und Weißes Moor”).

Since the water of the big lake (Fig. 1) is surrounded by a bog, it is rich in humic substances, therefore very acid  (pH 4.5-5) and not suitable for fish. However many other animals can thrive in such conditions – so here we can find various water bird species, snakes, like the grass snake Natrix natrix, frogs (Fig. 2), dragonflies and even bats in the evenings.

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Fig. 1 The big lake (Großer Bullensee)
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Fig. 2 A frog captured at the border of the big lake

Typical plant species found near the shore are the bulrush or Typha latifolia, the water-dropwort (genus Oenanthe), Fig. 3a,  the bog arum or Calla palustris, Fig. 3b and the carnivorous plant Drosera anglica.

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Fig. 3a The bulrush and the water-dropworth; Fig. 3b The bog arum.

The small lake (Fig. 4a and b) is accessible by a trail with informative panels made by the Nabu association. It is positioned north of the big lake, surrounded by a pine forest and blueberry bushes which densely grow at the forest floor (FIg. 5a and b).

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The lake can be observed only by a certain distance since this environment is very vulnerable and the soil is muddy and soft, so it can easily trap you.

Various water bird species can be found, the most common are the tufted duck Aythyla fuligula, the mallard Anas platyrhynchos and the Eurasian teal Anas crecca.

Photos by Ingrid Ugussi Vukman

Visiting Northern Istria

It was a slightly  cloudy day in mid-May when I decided to visit the northern part of Istria (Croatia), between Mount Ucka (Fig. 1) and the mountainous plateau of Cicaria, which is an extension of the Dinaric Alps. The area is mostly uninhabited, wild and largely untouched. Flower-rich wheat meadows are dominant here; in the past they were (most probably) pastures. Today they provide habitats for bees, butterflies, grasshoppers, spiders, mammals, reptilians and so on. Among flowers, I recognized Polygala nicaensis, members of the genera Ajuga and Ranunculus, various orchid species and, of course, grasses. Among orchids, I found Orchis puprpurea (Fig. 1 and 2), Orchis tridentata (Fig. 3), the very common and widespread Orchis morio, the delicate Cephalanthera longifolia and the non-photosynthetic Neottia nidus-avis, which prefers shady places along the nearby deciduous woodland.

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Fig. 1 Orchis purpurea and the Mount Ucka in the background.
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Fig. 2 Orchis purpurea
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Fig. 3 Orchis tridentata

Given the altitude and the higher soil moisture level, the plant communities present here are the typical sub-mediterranean ones. Therefore, I had the pleasure to meet some butterfly species for the first time, one of those meriting a special attention: Everes alcetas (Fig. 4) or the Provencal short-tailed blue. It is a member of the Lycaenidae family which, although occuring sporadically, it is common across the central Europe.

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Fig. 4 A couple of Everes alcetas standing on a pillow of tiny purple flowers of the genus Thymus.

In general, they feed on plants of the genus Medicago, Coronilla varia and Galega officinalis where they lay their eggs. They prefer bushy and sunny places but in Istria are very local and spotted by me only in this location.

One butterfly species that I encountered in the same area is the marsh fritillary (Euphydryas aurinia), a member of the Nymphalidae family (FIg. 5 and 6). This species is in decline in Europe, and is protected under law in the United Kingdom. However I managed to see them quite abundantly in many sites around Istria; perhaps because their habitat – the damp heathy grasslands – is still pretty intact in this region.

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In the same place I found another very peculiar butterfly species: Southern Festoon (Zerynthia polyxena), member of the Papilionidae family (Fig. 7).

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Fig. 7 Zerynthia polyxena

This is a widespread species, present in the central and southern Europe. However, it is very local and in Istria I found it only here. Larvae feed on members of the Aristolochia genus and in some areas, for instance in Hungary, it is restricted to only one Aristolochia species: the Birthwort (Aristolochia  clematitis). The wings are yellow, a bit paler in females, covered with a gaudy pattern of several black bands and spots, with a distinctive black sinuous line at the margin. On the edge of the hindwings there are several blue and red warning spots. The body is black, with red warning spots at the side.

Photos by Ingrid Ugussi Vukman

 

 

Crab spiders of Marlera

A very common species of this region, and easily found hidden between flower petals: Thomisus onustus (Fig. 1) is a crab spider known also as the flower spider. In fact, this species and other members of the Thomisidae family don’t build a web – instead they wait hidden and camouflaged on flowers for a prey to come. When a flower-visiting prey arrives, they grab it with the long front pairs of legs and paralyse it with a venomous bite.

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Fig. 1 Thomisus onustus – white female (size up to 6-7 mm).

Females can change their colours according to the surroundings. They can be white, yellow or pink and the colour can change in couple of days so that it perfectly mimics the colour of the host flower (Fig. 2). Males are always brownish and never change their colour (Fig. 3).

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Fig. 2 Yellow form of a female on a pink flower. Sometimes they adapt their colour to the surronding.
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Fig. 3 Thomisus onustus – a male (size 2,5-3,5 mm) on Ornithogalum flowers.

Another member of the Thomisidae family, Synema globosum (Fig. 4), is also called Napoleon spider because of the black drawing that resembles the silhouette of Napoleon. Found on dry grasslands or forest edges in warm areas, often on red and yellow flowering plants (mostly members of the Apiaceae or Asteraceae  family).

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Fig. 4 Synema globosum with his prey, wich can be much larger. Usual prey are bees, butterflies and other flower visiting insects.

Light green hairy spider that can be found on hairy vegetation. This picture (Fig. 5) enables only to determine the genus, Heriaeus. To discern the species it is necessary to look at the dorsal drawings of the opisthosoma and sometimes even the genitals.

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Fig. 5 A member of the Heriaeus genus – the  green body is covered with white-yellowish spines.

Photos by Borjan Radolovic

Life in a brackish lake

In the Marlera plain region, very close to the seashore, a couple of small brackish lakes can be found (Fig. 1), that are created by rainfall during winter and by seawater brought by the big waves caused by the two typical Adriatic winds – the Sirocco (or Jugo) and Bora (or Bura), which are frequent in the Autumn/Winter period. This water is rich in Crustaceans, a prelibate food for birds like the dunlin (Calidris alpina), a migratory species which can be seen in this area for a very short period during late Autumn (Fig 2 and 3).

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Fig. 1 Small lake near the seashore where fresh and salted water mix.

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In summertime, the hot and dry weather leads to almost all of the water evaporating, therefore only small salty ponds can be seen (Fig. 4).

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Fig. 4 The lake at the beginning of July, when only small higly salted ponds are left.

Later in the sumer, no water is left and only crystalised salt remains. However, some halophile species like the plant Salicornia europaea (Fig. 5) and the insects of the genus Cicindela (tiger beetles, Fig. 6) are able to cope with such harsh conditions.

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Crabs that used to swim in the lake and small ponds are now all dead (Fig 7, 8).

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The insects attracts various predators such the common wall lizard, subspecies maculiventris. A nice specimen can be seen in the Fig. 9, inhabiting only Slovenia and Istria.

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Fig. 9 A lizard, member of the species Podarcis muralis maculiventris.

 

Photos by Borjan Radolovic