DETERMINATION OF THE RELATIVE AGE STRUCTU RE OF A POPULATION OF MICROTUS-ARVALIS (RODENTIA, ARVICOLIDAE) USING SKULL OR JAW MEASUREMENTS

The relative age structure of Microtus arvalis populations can be esta blished from skull or jaw measures, in order to compare structures est ablished from trapped animals with structures established from skeleta l remains, e. g. in Barn Owl (Tyto alba) pellets. Measures were made f rom animals bred in our laboratory. Stepwise regressions show that cor relation between the logarithm of age and linear combination of measur es are over 0.8. Discriminant analysis shows that two classes of age c an be easily distinguished. The limits of the method are discussed in conclusion. Generally, only comparisons of population structures at th e same season, in the same country, are possible. Then, the study of t he selective action of predation may be possible.