Done Cartilage as an Age Criterion in the Cottontail Rabbit
Bans Peter Thomen, Department of Wildlife Management
and
Otto A. Mortensen, Department of Anatomy
University of Wisconsin
This paper is a preliminary report on the progressive ossification of
the bones as an age criterion in cottontails. Ossification is expressed
by the gradual disappearance of the epiphyseal cartilage from the joints,
and its replacement by bony material.
Our purpose is to develop a test by which cottontails shot in late fall,
or trapped in fall and winter, may be classified into young and old, just
of Fabricius
as the bars4 is now used to classify game birds. The essentials are that
the test ment:
1. Be applicable either to live or dead cottontails
2. Be valid through the hunting season (mainly November) and
as far as possible into the trapping season (November to March)
3. Be applicable to some bone which hunters are willing to spare,
and can send in by mail from distant points.
Other Age Tests
1ider and Sowls have published a method of classifying cottontails for
age by examining the testes and uteri in eareasses. Their test seems to be
good into December, but is of course not applicable to live rabbits.
Dice and Dice2 worked out dentition tests for age. but these are
applicable only to very young rabbits.
Oar hope is to develop a test which can be applied to live rabbits by
X-ray of some standard bone, or to dead rabbits by either X-ray or gross