The frequency of traffic and crossings of brown bear (Ursus arctos L.) across roads on Romanija Mountain

Abstract

Brown bear (Ursus arctos L.) is the biggest indigenous beast in Bosnia and Herzegovina and it needs a large living space. Roads cause fragmentation of its habitat, which can lead to the isolation of certain parts of the population. The impact of roads on wildlife and protection measures are explored in depth in Europe, but none such study has been done in Bosnia and Herzegovina. Romanija Mountain region is an important bear habitat in the Republic of Srpska. The habitat is crisscrossed by a network of roads, and the objective of this study is to investigate the impact of roads on local bear population. Romanija Mountain is located in the eastern part of Bosnia and Herzegovina, the Republic of Srpska. Altitude goes from 660 m to 1652 m. The climate is typical mountainous of a humid type. The average annual temperature is 6.5 °C. The vegetation period lasts for 152 days. Limestone is main geological substrate and there are calcocambisols and calcomelanosols. Most of the Romanija Mt. is covered by mixed uneven-aged forests in which the most common tree species are as follows: fir, spruce, beech, white and black pine. Traffic frequency was determined by counting vehicles in two occasions (60 minutes each), every month in the period from 14 December 2008 to 31 December 2009 at the three experimental areas (highway M-19, regional road Sokolac-Kaljina and forest road Buječ-Kostreša). In the same period, at all sample plots, traces/prints of bears have been recorded, and the places where they crossed the roads were determined. Based on analysis of collected data the largest traffic frequency is determined on the highway M-19, then the asphalt road Sokolac-Kaljina and the smallest on the forest road Buječ-Kostreša. On the other hand, the greatest number of crossings of bears was registered on the forest road of Buječ- Kostreša, and the lowest on the highway M-19, which indicates that the higher the traffic frequency resulted in a smaller number of crossings of the bear and vice versa. The largest number of crossings was registered in July, August and September while crossings of the bear were not recorded in the months of January, February, November and December when the bears went denning. Openness of forests to roads on Romanija Mt. is 9.71 km/1000 hectares, which is significantly below the Western European average. In the area covered by the study, casualties of bears in traffic have not been recorded. Although deaths caused by traffic were not observed, roads certainly have a negative impact on the habitat of the brown bear population, primarily due to habitat fragmentation and limiting the movement of a bear. On the contrary, in Slovenia and Croatia, losses in transport significantly affect the reduction of number of bear population.