Bear Size ~

[brotherbear]

The northern interior grizzly bear Ursus arctos L. by Arthur M. Pearson.

Age determination: Previous authors have all referred to a change in the thickness of the annular zones which occurred at various ages in the specimens they studied. Craighead ( 1970 ) found that the narrower zones occurred first at 5 years of age. Similar timing was found by Mundy and Fuller ( 1964 ). On the other hand, Rausch ( 1969 ) found, in brown bears from Alaska, that the change in the thickness of the zones did not occur until the 8th or 9th year. In the Yukon, I found that the change in the thickness of the cemental zones was not a consistent feature but in no case did it occur before the 8th year. In some cases, the change did not occur until the 11th or 12th year. It is quite possible that the change in thickness of annulation is in some way related to the sexual maturity and/or growth patterns of the animal, because grizzlies do not reach sexual maturity as early in the north as they do in the south. However, this change in thickness is a definite feature of the cementum pattern in grizzly bear teeth, whatever its reason. In many cases it was quite easy to distinguish annular rings up to and including the change, but afterwards the annulations became very narrow and sometimes obscured.

...From a subjective inspection of the male sample, it appears that a break in the growth curve occurred at about 10 years of age. Therefore the male sample was divided into those 10 years and younger, and those over 10 years.

*Note: those under 10 years old ( adolescent ) and those 10 years old and up ( mature adults ). Reply