Table 3: Description and data source of the explanatory variables used in the study.

Variable typeVariablesData source


NominalVertebrates’ class The Iberian Fauna Project (  
Species 2000 (
Vertebrate’s order


Relative weight (quotient between weight and length)
Data source for fish’ morphology was obtained from FishBase ( and [70].
For amphibians’ morphology, we used García-París et al. [75] and Pleguezuelos et al. [71].
For reptiles’ morphology we used Salvador [76].
For birds’ morphology we used Díaz et al. [77], Martí and del Moral [72], and Tellería et al. [78].
For mammals’ morphology, we used, Palomo et al. [73], and Rodríguez [79]. Additionally, we based Cetacea data in Kiefner [80].
Relative eye size (quotient between eye size and length)[8183]