The effect of sex, age, and location on carnivory in Utah black bears (Ursus americanus)
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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.
KeywordsStable isotopes Trophic level Carbon Nitrogen Ungulates
We would like to acknowledge the help of all the hunters who submitted hair and vestigial tooth samples to the Utah DWR and the assistance of the Utah DWR in collecting those samples and the associated data. We thank Craig McLaughlin, now at the Colorado Division of Parks and Wildlife, for locating ungulate counts for hunt units. Finally, we would like to thank Amanda Loveless, Hailey Billings, Eric Olson, Joycelyn, and Vanessa Dewey for their help in prepping samples.
Author contribution statement
KAH was primarily responsible for originating the idea behind the paper, the experimental design, stable isotope analysis of hair samples, data analysis, wrote substantial portions of the paper, and closely supervised and mentored KAK. KAK revised and rewrote significant portions of the paper and did significant library research to expand and update the citations in the manuscript. BLR, HB, and JA contributed significantly to the process of designing the experiment with BLR helping with stable isotope analysis of hair samples and revisions of the manuscript HB and JA helped extensively with arranging contacts with individuals at the Utah Department of Wildlife Resources (UDWR), obtaining data and maps from the UDWR and arranging the data for analysis, and revising the manuscript. KB arranged for the collection of hair and teeth samples from Utah bear hunters, the analysis of the teeth for aging, obtaining hunt unit maps of Utah, obtaining hunt unit data on bears killed within hunt units, ungulate numbers within hunt units, and hunt unit areas.
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