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A Technique for and Risks Associated with Entering Tree Dens Used by Black Bears

Cale L. Godfrey, Kim Needham, Michael R. Vaughan, Jennifer Higgins Vashon, Dennis D. Martin and Gerald T. Blank, Jr.
Wildlife Society Bulletin (1973-2006)
Vol. 28, No. 1 (Spring, 2000), pp. 131-140
Published by: Wiley on behalf of the Wildlife Society
Stable URL: http://www.jstor.org/stable/4617294
Page Count: 10
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A Technique for and Risks Associated with Entering Tree Dens Used by Black Bears
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Abstract

Entering dens to collect data is an important aspect of black bear (Ursus americanus) research. However, published literature does not describe or evaluate techniques for entering black bear dens. During winters 1995 through 1998, 109 of 151 (72.2%) radio-collared black bears in the George Washingtion and Jefferson National Forests, Virginia, used cavities in trees or snags as den sites. Safety concerns prevented us from attempting to enter 25 den trees, but we successfully entered 58 of 84 (69.0%) den trees and captured 166 bears (59 adults, 13 yearlings, and 94 cubs). Percentage of den trees that we entered differed among years (P=0.077). Tree cavities that were not safe to enter (n=12) and den abandonment (n=7) caused most (65.5%) failed attempts. Eight of 72 (11.1%) bears immobilized in tree dens died from handling. Twenty of 94 (23.1%) cubs were orphaned due to death of, or den abandonment by, the sow. Den trees that we attempted but failed to enter were taller (P=0.006), had a greater diameter at breast height (dbh) (P=0.004), and had higher cavity entrances (P=0.001) than den trees we successfully entered. Proportion of den trees falling after one year (P=0.308) and after 2 years (P=0.481) did not differ between trees we cut to enter and uncut trees. We encourage biologists to assess the value, risks and requirements for entering den trees and to report and evaluate other techniques to enter black bear dens.

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