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Black Bear Population Density Estimation Using DNA From Hair Snares As A Non-Invasive Mark Recapture Technique

Michael W. Whaley

AP Environmental Science, Pendleton High School

Results

Methods and Materials

Conclusions

Analysis Outputs

Advantages to NGS

Introduction

DNA collected from bears is an important tool in the research and management of the American Black Bear (Ursus americanus).

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Collecting DNA with hair snares is just one method of conducting mark-recapture studies that allow scientists to estimate a species population size.

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However, it has grown in popularity with the advancements in genetics technology. Also, it is considered a noninvasive genetic sampling (NGS) approach because the animals are not directly contacted by the researchers. Traditional methods often relied on live trapping, or darting the animals.

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The reduction in direct interactions between the subject animals and biologists helps to minimize biases.

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1. Researchers can study species without disturbing, handling, or directly observing them. This reduces risks to both the researchers and animals.
2. NGS techniques allow biologists to study populations of elusive and rare species.
3. NGS can potentially increase sample sizes by reducing: a) disturbances to animals, b) sampling efforts, and c) costs.

Bears have a highly developed sense of smell that is perhaps the best of all animals. As the photo of the skull shows, the bear has a massive opening into the nasal chambers for the intake of air which then passes over the olfactory receptor cells. The crinkly looking bone in the back of the nasal cavity is where the olfactory receptor cells are found. This area is one hundred times larger than in humans. This gives the bear a sense of smell about 7 times greater than a bloodhound.

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Researchers use this heightened sense of smell as a way to lure bears into a study area. Scent lures (tampons soaked in grape Kool-Aid and partially opened cans of sardines) were hung about 6 feet above ground. A single strand of barbed wire was strung about 17 inches above the ground, and in a rough equilateral of 20 ft X 20 ft. This forced the bears to either step over, or crawl beneath and where hair would be snagged. Cubs could walk under and not be counted in the population estimates.

Several bears were attracted to the area by the scent lures. This was confirmed with camera traps that collected still photos and videos. The above photo shows a large male crawling under the barbwire strand.

Snagged bear hair was collected and bagged and tagged to be sent to a laboratory for DNA analysis. Remaining hair was burned off with a torch to avoid confusion in subsequent sampling activities.

NGS is an effective method in the study of animal populations by biologists. It allows for the study of the animals without directly impacting them, and reduces bias by the observers. It also reduces the risk of injury or death to the scientists and/or the subjects being studied. With the advent of more affordable, faster, and accurate genetics technology, this method will grow in popularity.

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Figure 1: Microsatellite Chromatogram

Figure 2: Mitochondrial DNA Sequence

Figure 3: Mark – Recapture Formula