We modelled the distributions of two toads (Bufo bufo and Epidalea calamita) in the Iberian Peninsula using the favourability
function, which makes predictions directly comparable for different species and allows fuzzy logic operations to relate
different models. The fuzzy intersection between individual models, representing favourability for the presence of both species
simultaneously, was compared with another favourability model built on the presences shared by both species. The fuzzy union
between individual models, representing favourability for the presence of any of the two species, was compared with another
favourabilitymodel based on the presences of either or both of them. The fuzzy intersections between favourability for each species
and the complementary of favourability for the other (corresponding to the logical operation “A and not B”) were compared with
models of exclusive presence of one species versus the exclusive presence of the other. The results of modelling combined species
data were highly similar to those of fuzzy logic operations between individual models, proving fuzzy logic and the favourability
function valuable for comparative distribution modelling. We highlight several advantages of fuzzy logic over other forms of
combining distribution models, including the possibility to combine multiple species models for management and conservation
planning
