We conducted an aerial survey of larger wildlife species populations in two agricultural
landscapes of differing agricultural intensity in Slovenia – Ljubljansko barje and
Dravsko polje – using a drone with a mounted thermal infrared camera. We carried out
3 surveys in autumn 2024, winter 2025 and spring 2025. Using distance sampling
methods, we estimated the population densities of the two most common species; roe
deer (Capreolus capreolus) and European brown hare (Lepus europaeus). We detected
larger, though less stable populations in Dravsko polje. Hare densities were estimated
at 25,8 ind. / km2 in Ljubljansko barje and 30,5 ind. / km2 in Dravsko polje, and deer
densities at 31,7 ind. / km2 in Ljubljansko barje and 35,4 ind. / km2 at Dravsko polje –
these are among the first accurate density estimates for these species in Slovenia. We
used GLM analysis of spatial variables and analysis of space use data to identify a
significant negative impact of anthropogenic disturbances (such as urbanized area
extent) on both roe deer and hares. We also found a preference for meadows in Roe deer
and a preference for shorter and sparser vegetation types in Hare. We also detected
substantial densities of pheasant (Phasianus colchicus), red fox (Vulpes vulpes) and
domestic cat (Felis silvestris catus) in both areas with the addition of coypu (Myocastor
coypus), red deer (Cervus elaphus) and woodcock (Scolopax rusticola) in Ljubljansko
barje. The Red fox and Domestic cat seem to occur in similar densities in farmland, with
cat presence being positively affected by anthropogenic disturbances. Coypu were found
closer to waterways and Red deer closer to undisturbed forests. Our interesting findings
and accurate population estimates with low variance confirm the potential of UAV
application in wildlife research.
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