1st Conference on Resource Selection by Animals

Although all habitat-suitability modelling methods are inherently linked to the Hutchinsonian definition of the ecological niche, those based on the environmental envelopes are its direct geometrical application. Their common principle is to model in the environmental space, a hyper-surface, the envelope, encompassing all or part of the observation points. This paper compares four such methods: the first method based on the distance to the closest observation, or minimum distance. The second based on the frequency distribution of the observations on each dimension. The third and fourth are based respectively on the geometric and harmonic means of the distances to all observation points. We applied these four methods to the case of the Bearded Vulture (Gypaetus barbatus) in the Swiss Alps. An Ecological Niche Factor Analysis (ENFA) summarised the 14 environmental variables related to this bird into seven uncorrelated factors, which uses the dimensions of the environmental space. Eventually, a A-fold cross-validation process allowed us to compare and discuss these methods and their domain of application.