You may know
that the eruption-wear technique of ageing ungulates
compares the tooth wear of known age animals to the
tooth wear of harvested animals. Then estimating which
year class the unknown aged animal most closely fits
into.
The cementum-annuli (cross-sectioning
teeth) method of ageing deer, elk and other wild animals
is much different. It first requires decalcifying the
central lower incisors and then cutting cross-sections
of the root tips to a thinness measured in microns.
The slice of tooth is then placed on a slide and a special
dye is added to enhance viewing. It is placed under
a microscope. Circular lines within the tooth’s
diameter are readily visible and can be counted much
like the rings of growth on a tree, indicating a deer’s
age.
The question is how effective are each
of these methods for ageing deer and other ungulates?
To provide some insight we turned to the
scientific research of Hamlin, Pac, Sime, DeSimone and
Dusek as reported in the Journal of Wildlife Management
64(2):441-449. The researchers employed by Montana Fish,
Wildlife, and Parks wanted to increase their knowledge
on ageing wild ungulates to answer research questions
and improve management..
The eruption-wear part of the study was
done by six biologists that were experienced with eruption-wear
method of ageing of deer. Four of the biologists were
from Montana and two were from Washington. In one study
they aged 318 mule deer and 126 whitetails where each
animal’s age was known.
In a separate study, a western U.S. laboratory
whos researchers were skilled in the cementum-annuli
technique were assigned the task of ageing 108 mule
deer and 74 known age whitetails.
The results from this small but enlightening
study were fascinating. It showed that the trained wildlife
biologists employing the eruption-wear technique were
correct on 54 of the 126 whitetail deer or 42.9 % of
the time. The scientists that were using the cementum-annuli
method were correct on 63 of the 74 known age whitetails
for a success rate of 85.1 %. Furthermore the eleven
whitetails that were missed using the Cementum-Annuli
method were off by only one year.
Whereas 72 of the 126 animals were judged
incorrectly using the eruption wear method by skilled
wildlife biologists. Many of their estimates were off
by 2 years and often by as many as 3 years of age.
The results were especially poor for the
eruption wear technique in older animals. There were
12 bucks in a group of 6 and 7 year old known age animals
. Only one was correctly estimated using the eruption
wear method for a success ratio of 8.3 %.
The eruption wear technique may be O.K.
for some management purposes but it is less than adequate
for the curious hunter that shot a dandy buck or those
managers that require specific results.
The results clearly indicate that the
cementum -annuli method is greatly superior to the eruption-
wear technique for overall accuracy as well as accuracy
in the ageing of older animals
It’s much like the old saying in
that you get what you pay for. Even with skilled specialists
judging hundreds of animals each and every year the
success rate using the eruption wear method wasn’t
outstanding.
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