Abstract
Global climate change affects many species and contributes to the exceptional population growth of wild boar populations and thus to increasing human-wildlife conflicts. To investigate the impact of climate change on wild boar populations we extended existing models on population dynamics. We included for the first time different juvenile conditions to account for long-lasting effects of juvenile body mass on adult body mass and reproductive success. Our analysis shows that incorporating phenotypes, like body mass differences within age classes, has strong effects on projected population growth rates, population structures and the relative importance of certain vital rates. Our models indicated that an increase in winter temperatures and food availability will cause a decrease in mean body mass and litter size within Central European wild boar populations. We further analysed different hunting regimes to identify their effects on the population structure as well as their efficiency in limiting population growth. While targeting juveniles had the lowest effect on population structure, such strategies are, however, rather ineffective. In contrast, culling predominantly yearlings seems very effective. Despite being equally effective, only focusing on adults will not result in a reduction of population size due to their low proportion within populations.
Highlights
Global climate change affects many species and contributes to the exceptional population growth of wild boar populations and to increasing human-wildlife conflicts
To investigate the effect on population growth and structure we focused on the following culling regimes: (i) a totally unselective hunt (HMR of all age classes are the same); (ii) a highly selective hunt on only one of the four classes with hunting mortality rates (HMR) = 0 for all other classes, to identify the effect of removing individuals of each age class separately, and (iii) three culling regimes mimicking natural predation with a low HMR of 25% for classes older than one yearand differential selection among juveniles (i.e., HMR of juveniles ranging from 0 to 1 with NH1: no selection among juveniles, NH2: selective removal of heavy juveniles only, and NH3: selective removal of light juveniles only)
No qualitative changes to the model outcome could be identified except for two scenarios: First, under the unlikely assumption that body mass would not affect juvenile survival under unfavourable environmental conditions (Fig. S8, S10; Supplementary Information 2); Second, if the difference in survival between LJ and HJ fell below 20%, the proportions of LAJ and HAJ females within the population could be affected under unfavourable conditions (Fig. S12; Supplementary Information 2)
Summary
Global climate change affects many species and contributes to the exceptional population growth of wild boar populations and to increasing human-wildlife conflicts. Our models indicated that an increase in winter temperatures and food availability will cause a decrease in mean body mass and litter size within Central European wild boar populations. While many species decline in abundance and distribution others cope well with climate change and thrive[1,5,6] The latter typically reach high population densities, expand their distribution range and might cause severe human-wildlife conflictssuch as agricultural damage, the spread of diseases, negative effects on other species, or an increased risk of traffic collisions[7]. In order to investigate how favourable conditions affect wild boar population structure and dynamics we extended and refined previous population models[14,16,22] and developed an age-body mass hybrid Leslie matrix model[26]
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