There is only one winner: The negative impact of red deer density on roe deer numbers and distribution in the Slowinski National Park and its vicinity

Red and roe deer are the most numerous cervids in Europe, and they occur in sympatry in most regions. Roe deer were considered to be an inferior competitor in studies in which they co-occurred with fallow deer or muntjac. Despite the remarkable overlap of their ranges, there are few studies on the competition between the red and roe deer. Since interspecific interactions among ungulates are often related to their mutual densities, the current study focused on the effects of high red deer density on the roe deer numbers and spatial distribution in the unhunted Slowinski National Park (SNP) in northern Poland and forest districts open to hunting bordering the park. Using fecal pellet group counts, it was found that in the forest districts (where red deer densities were 2-3 times lower than in the SNP), roe deer densities were significantly higher than in the park. The red-to-roe deer density ratio was 10.8 and 2.7, in the SNP and the surrounding forest districts, respectively. Moreover, in the SNP, the roe deer distribution was negatively affected by the red deer habitat use, while in the hunting areas, such an effect was not recorded. The negative influence of the red deer on the roe deer population in the park was most probably due to the red deer impact on food availability. The biomass of the plant groups forming the staple food of the roe deer (Rubus spp., forbs, dwarf shrubs) was significantly higher in the fenced plots than in the unfenced ones. Lack of hunting in the protected areas may benefit only some species in ungulate assemblages which, in turn, may contradict one of their objectives-to maintain viable and ecologically functional populations.

Automated summary

Red deer and roe deer are the most common cervids in Europe, co-occurring in most regions. While roe deer were considered inferior competitors in the presence of fallow deer or muntjac, this study found that high red deer density negatively affected roe deer distribution and abundance in the Slowinski National Park in Poland. This impact was likely due to red deer's influence on food availability, resulting in higher roe deer densities and higher biomass of their staple foods in areas with lower red deer densities.