Wild boar in focus: Review of existing models on spatial distribution and density of wild boar and proposal for next steps

Abstract

This report provides a review of existing models for predicting the spatial distribution and abundance of wild boar at various scales (global, continental, national and regional) in order to inform the development of a new model to produce estimates of wild boar abundance at European level. The review identifies and discusses a range of models based on a wide variety of data types, corresponding to those targeted by the data collection model set by ENETwild, such as occurrence data (presence-only, presence-background and presence-absence), hunting bag data and density data. The reviewed models are categorised in two main groups, the first based on occurrence data to predict a distribution of wild boar, and the second based on hunting bag, census and/or density data to directly model abundance. Owing to the diversity of methodologies, an ensemble modelling approach is here proposed for combining the outputs from a range of complimentary models and generating density estimates of wild boar at European scale. This would retain the flexibility necessary to utilise all available data whilst maintaining a robust output. An initial model has been outlined which uses occurrence data to generate wild boar distribution across Europe. The resulting suitability scores are related to available density estimates to establish a relationship, so the suitability map can be converted into a map of absolute density. In order to further utilize other types of data in this framework, the produced outputs of prediction of habitat suitability or presence/absence are used to underpin models based on available abundance data (hunting bag, census or density).