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Large carnivores, placed as a rule on the top of the ecological pyramids, need relatively large habitat areas for life. The size of the home range of only one pack of wolves in Croatia may be from 80 km 2 to 160 km 2 .
In Scandinavia , where habitats are poorer, the home range size may even exceed 1,000 km 2 . Neither a wolf nor just a few packs of wolves should be isolated from other packs. Otherwise this would result in the interruption of the gene flow, in mating of relatives and, consequently, in the reduction of the diversity of the segment of population isolated in this way, making it more vulnerable to habitat changes.
The presence of carnivores in a habitat is the indication of its level of preservation. If we manage to preserve carnivores, it means that we have also managed to preserve its habitat including the entirety of the plant and animal life that it supports.
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| Roads and large carnivores |
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All types of transport infrastructure - railways, canals and roads - affect substantially and multiply the animal habitats that they pass through and thus the animals too. The barrier effects are felt in places where animals are prevented from crossing a road by the structure of the road, by a fence or the traffic itself. Major negative impacts of roads are a direct loss of habitats, habitat and population fragmentation, habitat quality degradation, immediate road-kill of animals trying to cross the roads and a threat to passengers themselves (collision with a large animal).
n the last five years many kilometres of new motorways have been constructed in Croatia , linking the country's interior with the northern and southern coastal area, passing through Gorski kotar, Lika and Dalmatia and intersecting the length and breadth of habitats of large carnivores and all other animals.
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Those motorways need have been constructed, but in order to minimize the negative effects specific extra facilities should have been built and numerous planned facilities adapted. The most recognizable special facilities are the so-called "green bridges" , structures that make it possible for animals to cross motorways.
Apart from green bridges many viaducts and bridges were constructed and extended only to allow easier passage for large animals. In the period between 1998 and 2004 six green bridges in the length from 105 to 200 m were constructed and intended primarily for the safe passage of large carnivores. In order to serve this purpose they had to be given a special form and size and located in specially selected places. This implies the knowledge of large carnivores' biology and way of life, of their movement patterns, activities and habitat use. Fortunately, this knowledge was made available by the research project entitled "Large Carnivores of Croatia" and managed by Prof. Dr. Đuro Huber. The project was run to collect information on the habitat use and especially on large carnivores killed on roads and their impacts on the animals' movement. This information was subsequently incorporated into environmental impact studies and applied during construction of crossings - green bridges on new motorways in Croatia . |
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The Ivačeno Brdo green bridge (120 m long) at the motorway section between Bosiljevo and Josipdol, one of the six green bridges constructed in Croatia from 1998 to 2004 (Photo by Đuro Huber) |
| Motorways constructed through Gorski kotar and Lika cross the habitats of bears, wolves and lynxes, When deciding on the sites for green bridges account was taken of the requirements of the bear as the country's largest and, regarding habitats, the most demanding carnivore. The five green bridges constructed are primarily intended to ensure connectedness of bears on opposite sides of the motorways. |
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| New motorways in Croatia link the interior with the northern littoral area and Dalmatia , but at the same time intersect the length and breadth of large carnivores' habitats. The arrows indicate places where special crossings (green bridges) for large carnivores are constructed. |
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| Wolves in Dalmatia safeguarding the habitat integrity |
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Of all large carnivores Dalmatia is inhabited by wolves only. Their presence as a threatened and protected species was an argument to construct one green bridge and several viaducts. The research into wolves in Dalmatia (see the link above) showed, among other things, that by motorway construction a valley named after wolves - the Vučevica valley - will be most affected. This valley lies in a straight line only 5 km far from the densely inhabited area of Kaštela, situated immediately behind the Kozjak Mountain and practically uninhabited.
The bleak rocky areas are here overgrown by densely interwoven forest of pubescent oak and oriental hornbeam accompanied by Jerusalem thorn and other underbrush, which make the valley practically impassable. On the west side of the valley, close to the pit Kevina, there were visible remnants of a Roman road disappearing after some time completely in the dense vegetation. The only passage through the valley was a narrow path that in some places also vanished completely in the dense plant cover.
Before the motorway construction, the valley was a core territory and a safe refuge for a wolf pack named Vučevica pack. The she-wolf named Anja and the wolf-cub Berni were members of this pack. The pack used to spend most of the time in this valley, where from year to year they kept their den, a place to breed a new generation of cubs.
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| The Vučevica valley before it was crossed by the motorway. From the other side of the Kozjak Mountain Split may be seen. Before the construction of the motorway the valley was a home for a wolf pack |
| The completion of the motorway in 2004 included also the construction of three special viaducts (Bejići, Rodine glavice, Podgrede) and the Osmakovac green bridge linking the wooded areas of the Kozjak Mountain and Opor with the country's interior. This connectedness will be of benefit not only to wolves, but also to all other animals inhabiting the Kozjak massif. It will also facilitate migration and arrival of other animals that might find the Kozjak Mountain a suitable habitat once the adequate conditions are created. |
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| Locations of the she-wolf named Anja and the Vučevica pack in the area of the Vučevica valley and Radošići in the period from 1999 to 2001. The completion of the motorway in 2004 included also the construction of three special viaducts (Bejići, Rodine glavice, Podgrede) and the Osmakovac green bridge linking the wooded areas of the Kozjak Mountain and Opor with the country's interior. |
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| A view of the Vučevica valley and the area of the Osmakovac green bridge - status in autumn 2004. At that time the bridge surface finishing works were not completed yet. |
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| The Osmakovac green bridge (200 m in total) is the longest of all six facilities of this type constructed in Croatia by the end of 2004. After the protective dams will have been constructed and the area planted with trees, it will be ready for the passage of wolves and other wildlife. |
| The construction of motorways and other infrastructure facilities is an inevitable fact. Fortunately, the natural wealth of Croatia remained for the most part preserved until the beginning of the 21 st century. However, we cannot rely on luck any more, because globalization and approaching Europe entail phenomena and processes that contributed substantially to the reduction of biological diversity and disappearance of some species, including the large carnivores, from the developed West-European countries. By constructing green bridges and other accompanying facilities suitable even for large carnivores we make it possible for them and all other species present in the respective area to remain a constituent part of Croatia 's natural wealth. Author: Dr. Josip Kusak, Department of Biology at the Veterinary faculty of the University of Zagreb, Croatia
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