Abstract
Before determining age ratios from samples of wild mink, Mustela vison, it is essential to establish some criteria for the females. A report (Lechleitner, 1954) that a supra-sesamoid tubercle was present on the femur of adults of both sexes and absent on juveniles appeared promising. The use of the baculum for distinguishing juvenile and adult males has been established (Petrides, 1950; Elder, 1951).