Biology_of_Mustelids_Vol_1.pdf

dimensions of o~d
53.
females often coincide with those of subadult males.
Then there remains only the risk of classifying a very small adult, or
even old male skull, as a female.
Next,
by using a combination of surface and structural features
(the appearance of the surface of the bones, and development of the crests
and prominences), the adultus and senex groups can be distinguished.
In
doubtful cases the shortened table will nave to be used, especially if
material, however small, for the particular sUbspecies is available for
comparison.
Senex skulls can easily be determined by the state of the
teeth, especially the canines. Severe wearing down of the ~remolar and
molar teeth indicates extreme old age in the ermine.
Wearing down of
only the canines indicates a younger animal, and its degree depends on
age.
Wearing down of the canines because of old age must be distinguished
from injury to the teeth resulting from attempts to bite their way out of
the trap, snare, cage, etc.
Finally, if the material is labelled and the dates of trapping
are.given, the age of the animals in the subadult group can be estimated
with an accuracy of less than 1 month.
It can be concluded from this brief analysis of the material
available for study, that the existing diag~oses
of subspecies are very
inaccurate, for even if they are based on large series of skulls, the age
composition of the series is heterogeneous.
True geographical variation
can be established only in material homogeneous with respect to age, and
diagnoses of each age group of the aubspecies to be described must be
given.