Genetic Tagging of Free-Ranging Black and Brown Bears
Genetic Tagging Overview
Authors: John G. Woods, David Paetkau, David Lewis, Bruce N. McLellan, Michael Proctor, Curtis Strobeck
Source: Wildlife Society Bulletin, Vol. 27, No. 3, Autumn 1999
Goal: Investigate genetic variability in black and brown bears and develop methods for genetic sampling in free-ranging populations.
Challenges in Identifying Wildlife
Difficulty in identifying individual animals due to:
Lack of distinguishing features (e.g., scars, unique color patterns)
Poor visibility in dense environments
High costs and invasiveness of physical capture
Risk of mark loss over time
Advances in Genetic Analysis
DNA Analysis Technology: Provides non-invasive individual identification methods.
Study Focus: American black bears (Ursus americanus) and brown (grizzly) bears (Ursus arctos) in the Columbia River Basin, British Columbia.
Used microsatellite genotyping at 9 loci for analyzing genetic variability in tissue and blood samples from captured bears.
Methodology of Hair Collection
In three field trials, various methods were employed to collect hair samples from free-ranging bears.
Techniques:
Barbed-wire enclosure hair-traps were found to be superior in collecting suitable hair for DNA analysis.
Processed samples included extracting DNA from hair roots.
Species Identification: Conducted using mitochondrial DNA (mtDNA) testing.
Sexing Samples: Utilized Y-chromosome testing.
Applications of Genetic Analysis
Developed statistical functions for match probability based on potential family relationships among samples:
Prandom: Random sampling
Ppar-offs: Parent-offspring groupings
Psib: Sibling presence
Psib was utilized to meet statistical criteria for identifying individuals in mark-recapture studies.
Research Area and Trials
Study Area
Location: West Slopes Bear Research Project around Golden, British Columbia, covering 5,000 km².
Preliminary Analysis
Genetic variability assessment established using nDNA from captured bears.
Hair sample collection effectiveness pre-tested on immobilized bears using barbed wire.
Field Trials
Trial 1:
Installation of hair-trapping stations in Glacier National Park.
Total hair samples collected: 293; Samples suitable for analysis: 170.
Genotypes passed threshold: 90% yielded usable data.
Trial 2:
154 hair samples collected; 85% provided sufficient genotypes for analysis.
Identified 33 individual bears from 118 usable samples.
Trial 3: Large-scale experiment producing 1,753 hair samples, achieving a genetic assessment of bear populations through sample analysis.
Statistical Methods for Genotype Matching
Need to establish statistical significance in genetic matching to prevent misidentification.
The study devised formulas to calculate match probabilities based on known relationships among sampled individuals.
Conclusion on Genetic Tagging
Genetic tags allow permanent and reliable identification of free-ranging bears.
Potential Applications Include:
Population censuses
Assessing genetic diversity and demographic structure
Understanding family relationships and ecological parameters.
Technology Refinement Needs: Focus on improving techniques, minimizing equipment weight, and enhancing the use of scent lures.
Acknowledgments
Mention of contributions from various individuals and institutions who assisted in the fieldwork and analysis, highlighting the collaborative effort in ecological research.