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The effect of sex, age, and location on carnivory in Utah black bears (Ursus americanus)

Hatch, Kent A., Kester, Kimberly A., Auger, Janene, Roeder, Beverly L., Bunnell, Kevin, Black, Hal L.
Oecologia 2019 v.189 no.4 pp. 931-937
Ursus americanus, adults, altitude, carbon, carnivores, dietary protein, foods, geographical distribution, habitats, hairs, life history, nitrogen, reproductive success, stable isotopes, teeth, ungulates, Intermountain West region, Utah
Ungulates are important to the diet of bears because they are high in protein, and the level of dietary protein strongly influences bear size. The size a bear obtains as an adult influences important life history characteristics, such as age of reproduction and reproductive success; therefore, it is important to know what foods are available to bears and how they are utilizing them. We tested hypotheses concerning the effect of age, sex, and location on black bear carnivory. We collected hair and vestigial premolar teeth from 49 Utah black bears, Ursus americanus according to the Utah Division of Wildlife Resources hunt unit. Hunt units differed in habitat quality and local ungulate density. We analyzed a vestigial premolar for the age of the bears and used analysis of the δ¹³C and δ¹⁵N values of the hairs of each bear to infer the degree of carnivory. δ¹⁵N of black bear hairs was positively correlated with increased availability of ungulates. There was a positive relationship between the δ¹⁵N of bear hairs and age in hunt units with the highest ungulate densities only. The δ¹⁵N and δ¹³C of black bear hairs were positively correlated, suggesting that bears are more carnivorous at higher altitudes. This study demonstrates the value of stable isotope analysis in understanding the feeding ecology of bears over broad geographic ranges. It demonstrates that ungulate availability is important to the feeding ecology of black bears in the Intermountain West.