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

  1. 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.

  2. Trial 2:

    • 154 hair samples collected; 85% provided sufficient genotypes for analysis.

    • Identified 33 individual bears from 118 usable samples.

  3. 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.