Six years of estimating roe and fallow deer density with distance sampling at the Koberg estate

Sammanfattning: Data about the big ungulates, particularly the European fallow deer (Dama dama dama) and the European roe deer (Capreolus capreolus) have been collected at the Koberg estate (Västra Götaland County, Sweden) using distance sampling as the inventory method. The project has been running for six years (2007 – 2012) and this is the fist time where all data from all years has been merged in one study. The main aims of this study was: (1) to investigate if the fallow deer and the roe deer density have decreased or increased during this period, (2) calculate the encounter rate, (3) investigate the quality and credibility of the estimated densities based on the results, (4) determine however the distance sampling method (line transect sampling) was the most suitable inventory method at Koberg and (5) to descriptively consider if the density estimates indicate reasonably similar trends as expected from the variation in the number of dead animals each year. The software used to analyze all field data was Distance 6.0. The results showed large variations in both species over the years with variable reliability. It was an expected result that the fallow deer density decreased in both areas after the hunt 2007/2008. But it was not an expected result to indicate such low density values for both species. Even if the result did not establish fully reliable estimates was this study not a waste. It still indicates population increases or decreases and the total number of individuals (N) with a known uncertainty in the whole area which is important information for the hunters and landowners for planning following years hunting.