Mortality rates of wild boar Sus scrofa L. in central Europe

In many parts of Europe, wild boar Sus scrofa population increase, and thus, high densities and dispersal into new areas are accompanied by economic problems. Due to many factors like insufficient hunting strategies as well as underestimation of population densities and reproduction rates, harvest rates seem to be insufficient. Thus, we calculated mortality rates of several wild boar populations from 1998 to 2009, to show the efficiency of hunting within several studies distributed over eight European states. For calculating mortality rates, the daily probability of survival of radio telemetrically observed wild boar was analysed according to Mayfield (Wilson Bull 73:255-261, 1961) and with survival analysis in R for three age classes (0, 1, ≥2 years) and both sexes. The mortality rates of wild boar per annum, especially piglets, were comparably low (about 0.5 for piglets and similar for total population). About three third of all observed animals survived at least until the next period of reproduction. Mortality rates differed between some study areas, the sexes and age classes. The sex ratio of the shot piglets equals the sex ratio of captured piglets; there seems to be no sex-biased hunting in this age class, but in an older age. Shooting was the main cause of death; only very few animals died by natural causes, e.g. diseases. The comparative analysis of all studies reflects a low mortality of wild boar in highly productive populations. Our results certified the findings of several studies that predation, natural mortality, and road mortality have only small impact on wild boar populations, whereas especially, nutrition or hunting are mainly decisive. Assuming net reproduction rates of more than 200 % according to literature data, our results indicate that harvest rates are not sufficient at our study sites. In all our studies, mortality rates and, thus, harvest rates are less than the assumed total net reproduction. Especially, the harvest rate of piglets seems to be insufficient. Thus, the population will increase further. High reproduction has to be counteracted by regulating mainly the reproductive animals. For regulating a population, combined and effective hunting methods have to be conducted to harvest at least the net reproduction. Thus, we recommend higher hunting rates of piglets (80 % of the offspring should be harvested) and of adult females. Intensified hunting of piglets by drive hunts and at an early age as well as intensified single hunt on adult females might help regulating wild boar populations.