Progress 10/01/03 to 09/30/09
Outputs
OUTPUTS: DNA-based capture-mark-recapture techniques are commonly used to monitor wildlife populations. Analyzing all collected samples can be cost prohibitive for studies of high-density populations, therefore subsampling is frequently used to offset genetic analysis costs yet obtain reliable population abundance estimates. Because model selection and parameter estimation depend on sample size, choosing an appropriate subsampling procedure is a critical part of study design. Monitoring high-density populations at large scales can be logistically challenging and may require estimating population density at small scales and extrapolating to larger areas. Density estimates must be precise and robust to closure violations common to small-scale studies. We used DNA-based capture data for a black bear (Ursus americanus) population in Great Smoky Mountains National Park, Tennessee to investigate the effects subsampling has on model selection. We incrementally reduced the number of sites each week from which 1 sample was selected for DNA analysis to generate subsets of a full dataset and compared capture summary statistics, model selection, and bias and precision of model-averaged estimates with results from the full dataset. We also evaluated a spatially explicit mark-recapture method for estimating density for a relatively small study area located in contiguous black bear habitat. We assessed the degree of violation of population closure and compared density estimates from a conventional abundance conversion method with estimates from the spatially explicit method. Our results indicated intermediate levels of subsampling (e.g., selection of ~50% of sites/week) caused the greatest uncertainty in selecting the best models. Bias of model-averaged estimates rapidly increased as the number of samples analyzed decreased with a >50% chance of deriving a biased estimate when <70% of sites were selected. Population closure was violated in our study and likely caused positively biased density estimates compared with estimates obtained from the spatially explicit method. Based on the full dataset, spatially explicit estimates exhibited levels of precision acceptable for extrapolation to larger areas. PARTICIPANTS: Michael R. Pelton, Professor Emeritus, University of Tennessee Frank T. van Manen, Adjunct Associate Professor, University of Tennessee Joseph D. Clark, Adjunct Professor, University of Tennessee Jared Laufenberg, Graduate Research Assistant, University of Tennessee Partner Organizations: National Park Service and Tennessee Wildlife Resources Agency TARGET AUDIENCES: State and federal wildlife biologists and managers. PROJECT MODIFICATIONS: No major changes in the research approach have taken place during the reporting period.
Impacts
Given ample spatial coverage of sample sites and number of sampling occasions, precise (i.e., CV ≤20%) and unbiased population abundance estimates can be achieved on smaller study areas through intensive subsampling efforts (i.e., selecting ≥1 sample/site for each sampling period). We suggest that reliable and cost-effective density estimates needed to monitor populations at larger scales can be obtained with the sampling design used in our study in combination with spatially explicit density estimation methods.
Publications
- Laufenberg, J. .S. 2009. Effect of subsampling on model selection and model averaging to estimate black bear population abundance. M.S. Thesis, University of Tennessee, Knoxville. (pending committee approval)
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Non-invasive genetic sampling to estimate the size of wildlife populations has received much attention during the last decade. Application of this technique for carnivores typically involves extraction of DNA from hair collected at specific sampling sites. These techniques were pioneered for bear populations. However, results from our research on American black bears (Ursus americanus) in the southern Appalachians indicated that a proper sampling design is crucial. From genetic data collected during 2003-2006, we concluded that DNA sampling for the specific purpose of population estimation would require substantial resources and would not be practical because black bear densities in the area are high, resulting in low capture probabilities (see Settlage et al. 2008). Sampling smaller areas, however, is feasible if a sufficient number of DNA samples can be obtained and analyzed per unit area. Therefore, we analyzed additional DNA samples during 2008 to increase sample sizes and to determine optimal sampling strategies for our study area. Sensitivity and population density analyses based on this expanded dataset are near completion and the final report is anticipated spring 2009. Additionally, we are collaborating with the Tennessee Wildlife Resources Agency to determine if DNA sampling using hair collected from glue traps can be used in combination with recaptures from bears harvested during the hunting season to provide accurate and precise estimates of bear population size. PARTICIPANTS: Michael R. Pelton, Professor Emeritus, University of Tennessee. Frank T. van Manen, Adjunct Associate Professor, University of Tennessee. Joseph D. Clark, Adjunct Professor, University of Tennessee. Jared Laufenberg, Graduate Research Assistant, University of Tennessee. Partner Organizations: National Park Service and Tennessee Wildlife Resources Agency. TARGET AUDIENCES: State and federal wildlife biologists and managers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Our study has demonstrated that wildlife managers need to consider proper sampling designs to estimate black bear population abundance. Thus, our findings have impacted how resource management agencies proceed with regional monitoring of black bears. As a result of this research, we are working in close collaboration with the National Park Service, the Tennessee Wildlife Resources Agency, and other agencies in the region to develop more reliable and cost-effective techniques to monitor population growth instead of population abundance. Field sampling procedures to test this new approach were developed based on a 2007 pilot study, which will be implemented once appropriate funding is obtained.
Publications
- Settlage, K., F.T. van Manen, J.D. Clark, and T.L. King. 2008. Challenges of DNA-based mark-recapture studies of American black bears. Journal of Wildlife Management 72(4):1035-1042.
- F.T. van Manen, J.D. Clark, and M.R. Pelton. 2008. Development of a DNA sampling technique to monitor black bear population growth in Great Smoky Mountains National Park. 2008 Great Smoky Mountains National Park Science Colloquium. (abstract).
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Non-invasive genetic sampling to estimate the size of wildlife populations has received much attention from wildlife managers and researchers. These techniques typically use DNA extracted from hair collected at specific sampling sites and were pioneered for bear populations, including the American black bears (Ursus americanus). However, results from our research indicated that a proper sampling design is crucial. From genetic data collected during 2003-2006, we concluded that DNA sampling across black bear range in the southern Appalachian region, for the specific purpose of population estimation, would require substantial resources and would not be practical. A journal article detailing this study was accepted for publication in the Journal of Wildlife Management and this important finding was disseminated to state and federal wildlife management agencies in the southern Appalachian region during bi-annual and informal meetings. In that articles, we point out that an alternative approach to population monitoring may be to estimate population growth, rather than population abundance. Primary advantages of that approach are that fewer assumptions are violated and standard bear monitoring techniques used by the National Park Service and state agencies (i.e., bait-station survey) may be modified to collect the hair samples. PARTICIPANTS: Michael R. Pelton, Professor Emeritus, University of Tennessee Frank T. van Manen, Adjunct Associate Professor, University of Tennessee Joseph D. Clark, Adjunct Professor, University of Tennessee Jared Laufenberg, Graduate Research Assistant, University of Tennessee Partner Organizations: National Park Service and Tennessee Wildlife Resources Agency TARGET AUDIENCES: State and federal wildlife biologists and managers. PROJECT MODIFICATIONS: No major changes in the research approach have taken place during the reporting period.
Impacts
Our study has demonstrated that wildlife managers may want to consider alternatives to region-wide DNA sampling to estimate black bear population abundance. Thus, our findings have impacted how resource management agencies proceed with regional monitoring of black bears. As a result of this research, we are working in close collaboration with the National Park Service, the Tennessee Wildlife Resources Agency, and other agencies in the region to develop more reliable and cost-effective techniques to monitor population growth instead of population abundance. Field sampling procedures to test this new approach were developed and implemented during 2007.
Publications
- Laufenberg, J., F.T van Manen, J. D. Clark, and M.R. Pelton. 2007. Long-term research and monitoring of black bears in Great Smoky Mountains National Park - 2006 Annual Report. Submitted to the National Park Service, Great Smoky Mountains National Park. University of Tennessee, Department of Forestry, Wildlife and Fisheries, Knoxville, Tennessee.
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Progress 01/01/06 to 12/31/06
Outputs
Non-invasive genetic sampling to estimate the size of wildlife populations has received much attention from wildlife managers and researchers. These techniques typically use DNA extracted from hair collected at specific sampling sites and were pioneered for bear populations, including the American black bears (Ursus americanus). However, results from our research indicated that a proper sampling design is crucial. Moreover, we conducted additional analyses in 2006 and concluded that DNA sampling across black bear range in the southern Appalachian region, although technically feasible, would require substantial resources and would not be practical (details of this study are provided in a manuscript by Settlage et al. submitted to the Journal of Wildlife Management). The main reason for this limitation is that bear density in the region is high. Therefore, we initiated a second research phase this year to determine whether non-invasive genetic sampling could be used to
estimate population growth, rather than population abundance. Primary advantages of that approach are that fewer assumptions are violated and standard bear monitoring techniques used by the National Park Service and state agencies (i.e., bait-station survey) may be modified to collect the hair samples. We hired a new graduate student this year to address this research topic. We conducted a pilot study this summer to determine whether a sufficient number of hair samples can be collected using this approach. We are currently conducting the DNA analysis of the collected hair samples.
Impacts
Our study has demonstrated that wildlife managers may want to consider alternatives to region-wide DNA sampling to estimate black bear population abundance. As such, our findings have impacted how resource management agencies proceed with regional monitoring of black bears. Consequently, we are now working in close collaboration with the National Park Service and Tennessee Wildlife Resources Agency to develop more reliable and cost-effective techniques to monitor population growth.
Publications
- Laufenberg, J., K. Settlage, F.T van Manen, J. D. Clark, and M.R. Pelton. 2006. Long-term research and monitoring of black bears in Great Smoky Mountains National Park - 2005 Annual Report. Submitted to the National Park Service, Great Smoky Mountains National Park. University of Tennessee, Department of Forestry, Wildlife and Fisheries, Knoxville, Tennessee.
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Progress 01/01/05 to 12/31/05
Outputs
Genetic sampling for mark-recapture is an emerging technique for estimating population abundance of wildlife populations, including the American black bears (Ursus americanus). These non-invasive techniques use DNA extracted from hair collected at barbed-wire enclosures. However, the efficacy of various sampling regimes for estimating population abundance has not been established so we investigated how the density of sampling sites, number of samples analyzed (subsample intensity), and sampling duration affect the accuracy and precision of population estimates. Field data were collected during 2003 and 2004 in Great Smoky Mountains National Park. We identified 129 (2003) and 141 (2004) individual bears using their unique genetic profile obtained from 9 to 10 microsatellite loci. Reductions in site density, subsample intensity, or sampling duration tended to produce low and biased capture probabilities, resulting in unreliable population estimates. Our results indicate
that effective implementation for black bear population estimation requires careful consideration of study design, particularly when population densities are high. Bias would be reduced by analyzing >25 subsamples each from greater or equal to 4 hair-capture sites/female home range, using a sampling duration of 6-8 weeks. A final report with recommendations was submitted to the Resource Management Division at Great Smoky Mountains National Park in September 2005 and a scientific article will soon be submitted to an appropriate journal.
Impacts
The results of our study clearly indicate that genetic sampling to estimate black bear abundance is feasible, but sampling intensity, duration, genetic markers, and population density are crucial considerations. Wildlife researchers and managers will be using the results of this study as guidance for the proper design of population monitoring studies. Resource management personnel at Great Smoky Mountains National Park will implement the results of this study and replace current populations monitoring techniques with non-invasive genetic sampling.
Publications
- Clark, J.D., F.T. van manen, and M.R. Pelton. 2005. Bait stations, hard mast, and black bear population growth in Great Smoky Mountains National Park. Journal of Wildlife Management 69:000-000.
- Settlage, K.E. 2005. Efficacy of DNA Sampling to Monitor Population Abundance of Black Bears in the Southern Appalachians. Thesis, University of Tennessee, Knoxville, Tennessee, USA.
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Progress 01/01/04 to 12/31/04
Outputs
We conducted our study in two study areas: the northwest portion of Great Smoky Mountains National Park in Tennessee(approximately 16,000 ha),and a southern study area on U.S. Forest Service lands in Georgia, South Carolina and North Carolina (approximately 32,900 ha). We established 64 sample sites in the northern study area and 57 sites in the southern study area. Each hair-capture site consisted of a barbed-wire enclosure with bait. All sites were checked for hair samples and rebaited once every 7 days for 10 weeks during summer 2003. We randomly chose up to 25 samples per weekly sampling period for DNA analysis in each study area. Microsatellite DNA sequencing was performed at Leetown Science Center (USGS). We used multiple mark-recapture models (closed models) to estimate population size using Program CAPTURE. During 2003, we collected 1,372 hair samples in Great Smoky Mountains National Park from 64 sites. The number of sites visited by week was highest during
the middle of the 10-week sampling period. A total of 205 DNA samples could be analyzed (82% success rate), representing 129 different bears. There were 117 sample matches representing 41 bears. As such, 88 bears were not recaptured. Using Program CAPTURE, we generated a preliminary population estimate (model Mh jackknife) of 291 bears (95% CI = 251-345) for the study area in Great Smoky Mountains National Park. In the southern study area, 57 sites yielded a total of 584 hair samples. Although the proportion of sites visited by week was lower compared with Great Smoky Mountains National Park, the temporal trends were similar. A total of 181 DNA samples could be analyzed (86% success rate), representing 60 different bears. There were 150 sample matches representing 29 bears; 31 bears were not recaptured. The preliminary population estimate for the southern study area (model Mh jackknife) was 103 bears (95% CI = 85-136). The preliminary findings of our study indicate that a sufficient
number DNA samples can be collected in an efficient manner. Although the sample sizes for the southern study area were lower than those from the national park study area, samples sizes from both areas were relatively large. The number of sample sites visited per week typically represented 30 to 80% of the total sample sites, providing a good sampling intensity. The precision of the DNA-based estimates was greater than those based on livecapture data. Moreover, samples from both study areas had sufficient amounts of DNA for sequencing, as indicated by a 82% success rate for the national park and a 86% success rate for the southern study area.
Impacts
Although genetic data can be effective to estimate population abundance of animal populations, optimal sampling regimes should be established before full-scale monitoring programs can be put into place. The preliminary results of this study indicate that DNA sampling to estimate black bear abundance is feasible, but that sampling intensity, duration, genetic markers, and bear density are crucial considerations. Wildlife researchers and managers will be using the results of this study as guidance to the proper design of DNA-based population studies.
Publications
- No publications reported this period
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