SUBJECT: Strategy and mitigation measures for reducing roe deer-vehicle collisions in Slovenia
AUTHOR: Boštjan Pokorny, ERICo Velenje, Ecological Research and Industrial Cooperation, Koroška 58, 3320 Velenje, Slovenia

In Slovenia, between 4000 and 6000 roe deer are killed on roads each year. Although this number represents an important factor of the mortality of the species (more than 15% of annual hunting bag) and presents a high risk for drivers, no mitigation measures have been systematically implemented on the national scale until recently. Therefore, deer-vehicle collisions were systematically recorded all over the country in the 1999–2001 period. Beside determination of the most problematic sections of Slovene main and regional roads, some statistical analyses were also performed. The most indicative results obtained by the analysis of 7759 records on roe deer road-killed in 206 hunting grounds (representing >60% of the Slovene surface) are as follows: (a) The frequency of deer-vehicle collisions (expressed by the average number of roe deer yearly killed on roads on every 1,000 ha of the surface) is the highest in sub-Alpine and sub-Panonic regions. (b) The risk for collision with roe deer vary over the year – the majority of crashes occurs in April and May; however, a risk is high during the summer and autumn as well. (c) The daily pattern of roe deer-vehicle collisions has a pronounced bimodal distribution with peaks in dawn (5 a.m. – 7 a.m.) and dusk (6 p.m. – 10 p.m.). (d) The risk for collision with roe deer is higher in fragmented landscape, while it is significantly lower both in forest and in agricultural landscapes.

Considering the recent situation, the strategy for mitigation of the problem of roe deer-vehicle collisions was defined. To achieve its main goal (50% decline in the number of collisions on the national scale), the most important issues will be done as follows: (i) testing of the effectiveness of different mitigation measures in a wide range of landscapes and habitat types, adjacent to roads; (ii) determination of the most effective countermeasures for each problematic section of Slovene main and regional roads; and (iii) implementation of adequate measures all over the country. In autumn 2004, testing of several mitigation measures (two modifications of deer warning reflectors, chemical repellents, averting roadside devices emitting ultrasound and terrestrial vibration, formal deer warning signs, and warning panels with dynamic/changeable content) started on 42 sections of roads, dispersed all over Slovenia. We hope that upcoming activities will significantly reduce deer and other wildlife mortality on roads; as such, these mitigation measures (which in principle do not influence animal spatial behaviour, i.e. migration patterns) should also have a positive effect on the conservation of biodiversity in the close vicinity of transportation corridors in Slovenia.