AGE DETERMINATION OF URSUS ARCTOS MIDDENDORFFI USING CRANIAL CHARACTERISTICS

Ms. Kalin A. Kellie
Dr. Joseph A. Cook




ABSTRACT

Determining the age of brown bears (Ursus arctos) is important to biologists interested in the age structure of a population. Private individuals are also curious about the ages of bears they have hunted.

Techniques have been attempted to age brown bears using skull characteristics, but results were highly variable due to small sample sizes and individual variation. Currently, the only trusted method of aging bears is tooth cemetum analysis. Unfortunately, this technique is costly, requiring much experience and/or expense. In addition, teeth sent to laboratories for analysis can take several months to be processed. I hope to find an simple, accurate method of aging brown bears. Cranial measurements require little time, and estimates can be obtained quickly. Because age estimation using cranial measurements doesn't require a tooth to be pulled, the skull can remain intact. Combining the bear skull collections of John Hechtel (Alaska Department of Fish and Game) and the University of Alaska Museum, I will be using a series of measurements to describe the development of Kodiak brown bear skulls (Ursus arctos middendorffi M.). Using a large sample size and multiple measurements, I will be formulating an equation that predicts the age of the bear. This equation will be tested on additional skulls to determine accuracy.

Age determination of newborns through age two has been well established by using the eruption of deciduous and permanent teeth. Because these skulls can be aged without cranial measurements, I will focus specifically on defining the age of late two through six-year-old bears. Beyond six years, the available sample size is too small for adequate age prediction.