Criterios para la determinación de la edad relativa en Arvicola terrestris monticola (Rodentia, Arvicolidae)

Resum

Criteria for relative age determination in Arvicola terrestris monticola (Rodentia, Arvicolidae)
Criteria for the establishment of relative age classes in the fossonal form of the northern water vole Arvicola terrestris, are given. These criteria are applied to 684 specimens (304 males, 380 females) of A. t. monticola captured in the Aran Valley (Spanish Pyrenees). The morphological and morphometrical features used in age determination in A. terrestris are shown, and the validity and precision of each one described. In the sample analysed six relative age classes are considered using the following characteristics: kind of coat and moulting stage, sexual stage, mandible and skull morphology and, as a particularity of the latter, the degree of separation between the interorbital crests. In a complementary way, the mean values and intervals obtained in each age class for head-body length, body weight, condylobasal length and diastema length are shown. From the litera ure, age intervals are established for each class.