Research on the Ecology and Natural History of Black Bears

The American black bear (Ursus americanus) is an important symbol of the parkand has significant intrinsic value to visitors. However, a dense bear population coupled with high visitor use can lead to frequent human-bear conflicts and require substantial NPS resources. Because of apparent scarcity of black bears during the late 1960s and the general lack of knowledge about this species, the Park requested the University of Tennessee in 1969 to determine (1) how many bears occurred in the national park and (2) how the population can be monitored over time. PIs have collected data on black bears in the park since 1969 to develop and test various techniques to estimate population size.  Population estimation and monitoring based on live-capture methods is labor intensive and estimates can be biased because individuals or groups of individuals exhibit different probabilities of capture (i.e., capture heterogeneity). A potential source of capture heterogeneity is the unequal exposure to trapsites between females and males because of differences in home-range size. In addition, we identified trap-shy and trap-smart responses to live capture as sources of capture bias. Recently, they also showed that changes in annual bait-station visitation, a population monitoring technique used by the NPS, did not correspond with estimated changes in population growth within our study area. Recent advances in molecular genetics may provide better alternatives to population estimation and monitoring. Identification of individual bears is possible by genotyping DNA from collected tissue samples (e.g., scat, hair, blood). Genetic sampling can increase capture probabilities, decrease tag loss, and reduce the effects of permanent trap response bias, potentially increasing the precision and accuracy of population estimates. 

They conducted a pilot study in 2003 and 2004 in the southern Appalachians to develop sampling protocols that would result in reliable estimates of population size. An important finding from that study was that it may be logistically impractical to apply DNA-sampling techniques to determine population size, even for relatively small areas. Because of the high bear densities in the national park, sampling intensity would need to be extremely high, requiring substantial personnel and financial resources. Instead of estimating population size, it may be more efficacious to estimate population growth. It is possible to estimate growth rates with high precision and low bias. Based on the findings of our long-term studies, we suggest that future monitoring of the black bear population may best be accomplished by replacing the bait-station surveys and population estimates based on live captures with DNA sampling to track population growth rather than population size. By continuing sampling according to the UT/USGS protocols but replacing live captures with mark-recapture information based on DNA samples, more rigorous monitoring of the black bear population can be accomplished. 

In 2005: Researchers estimate there are 200 bears, plus/minus 72 in northeastern part of GRSM.  

In 2006: researchers put radio collars on 18 female bears but were only able to find and visit 4 dens (2 tree dens and 2 ground dens). Only the females in ground dens successfully reproduced. Both had two cubs. PI estimated there were 227 bears, plus/minus 72 in northeastern part of GRSM.

No activity was conducted in 2010.

Tags: american-black-bear, aphn, appalachian-highlands-network, black-bear, ecological-framework-biological-integrity-focal-species-or-communities-mammals, ecology, great-smoky-mountains-national-park, grsm, grsm-permitted-study-id-grsm-00025, ser, southeast-region, ursus-americanus
Organization: Department of the Interior