Northern Rocky Mountain Science Center (NOROCK)
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Northern Rocky Mountain Science Center (NOROCK)
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Katherine C. Kendall, USGS Glacier Field Station, Glacier National Park, West Glacier, MT 59936-0128. kkendall@usgs.gov
Lisette Waits, Fish and Wildlife Resources, University of Idaho, Moscow, ID 83844-1136. lwaits@uidaho.edu
Grizzly bears (Ursus arctos horribilis) once roamed most of the North American Continent. Habitat destruction and direct conflicts with humans have reduced their range by 99% in the lower 48 states (right, click on map for larger version). Today, it is estimated that fewer than 800 remain south of the Canadian border. In 1975 grizzly bears were listed as threatened under the Endangered Species Act. The Greater Glacier Ecosystem may provide one of the only opportunities for long-term survival of this species south of Canada. However, many questions remain on how best to ensure the survival of this magnificent species.
Although it is generally assumed that the grizzly bear and black bear population densities in Glacier National Park (GNP) are higher than in surrounding areas, possibly approaching carrying capacity, studies of grizzly bears in two adjacent areas found no evidence of subadult emigration from the Park or of higher bear density near the Park border. It is likely that few, if any, bears range exclusively within the confines of the park throughout their life, or even within each year. Although they are fairly secure within Glacier National Park, when bears move outside the park boundaries, they are exposed to a variety of mortality risks. Because grizzly bear populations to the south and east of Glacier National Park are declining while a population to the northwest is growing, population trends in the park can not be inferred from neighboring areas. Black bear population trends in this region have not been studied.
The success of bear conservation efforts cannot be evaluated without reliable information on population trends. Until now, statistically rigorous population studies in forested habitat could only be accomplished with radio telemetry where large numbers of bears are handled. This impacts individual bears and the presence of collared/marked bears and frequent overflights impinge on park and forest visitor’s wilderness and solitude experiences. However, until recently, these methods remained the best available means for acquiring reliable population data. Recent advances in genetic techniques have opened the door to less intrusive approaches.
It is now possible to identify species, individuals, and gender with bear DNA samples from hair and scats. With appropriate design, sign surveys can be used to obtain an unambiguous minimum count and population index. Bear population density and sex ratio can be estimated from hair collected systematically at hair snag sites. The amount of genetic variation within the population can be described with materials from both sampling designs.
The study area spans 8000 km2 of land under multiple ownership within the Northern Continental Divide Ecosystem in Northwest Montana. Study design allows data from contiguous studies in Canada to be analyzed with data from the Greater Glacier Area study for a regional grizzly bear population estimate of an area covering more than 20,000 km2.
HAIR SNAGGING
The study area is divided into 126 - 642 km cells. One barbed wire hair snag is placed in each cell and baited with a non-rewarding liquid scent lure. Hair snags are revisited after 14 days and all hair is collected from barbs using tweezers, placed in paper collection envelopes, and stored in desiccation chambers. Snags are relocated to another site within each cell every two weeks for five snagging sessions. Remote cameras were placed at some hair snags to learn more about how bears behave at these sites (grizzly bears investigating scent lure at hair snags during 1998 field season). Population density will be estimated with mark-recapture models using DNA "fingerprints" of bears identified from hair snagging in conjunction with those identified from sign surveys.
RUB AND SCAT SURVEYS
Sign survey is comprised of two components: hair from trees, cabins, or sign posts that bears rub on and scat left by bears as they travel the trails. Surveys of all 1200 km (~730 miles) of maintained trails in Glacier National Park were conducted a minimum of three times per year in 1998 and every 14 days May-October, 1999 and 2000. Crews hiked the length of each trail segment looking for any bear sign deposited since the previous survey.
Rub Tree Surveys: During preliminary surveys, objects such as cabins and trees where bears rub were identified and marked. These were entered into a Geographic Information System (GIS) for assisting field personnel in relocating upon subsequent surveys. Information such as tree species, diameter, and distance from trail were also recorded. Over 750 rub objects were monitored during the study. To ensure better hair samples, each designated object has short pieces of barbed wire attached to the rubbing surface. All hair found on each individual barb is considered a separate sample. Using tweezers, samples are placed in paper collection envelopes and stored in desiccation chambers.
Scat Surveys: Three ml of each scat was collected and placed in 12 ml of 90% ethanol to minimize DNA degradation. Any remaining scat on the trail is removed to prevent collection of that scat during future surveys. Location, composition, and estimation of age are recorded for each sample.
SAMPLE PROCESSING
Hair Samples: Recent work has found that a single bear hair follicle yields sufficient DNA to identify species, individual, and gender. Prior to DNA extraction each hair sample is examined to identify and isolate intact follicles. Acceptable DNA extraction rates are achieved with hair samples with at least five follicles and are the standard for this project. The hair follicles (5-10) are inserted into a solution that will breakdown the protein coat that surrounds the DNA in the follicle. The samples are then repeatedly "washed" chemically to remove any cellular debris and then stored in a refrigerator until DNA analysis is conducted.
Scat Samples: Fecal samples include cells shed from the intestinal lining which contain DNA that can be extracted. Despite recent advances, however, scat has been used as a DNA source only in small scale or preliminary studies due to lingering technical problems. It is more difficult, and thus more expensive, to extract DNA from fecal samples than from hair follicles. This difference is due to the presence of smaller quantities of DNA, DNA degradation, and the presence of plant polysaccharides that inhibit the polymerase chain reaction (PCR) used to amplify the genetic material.
DNA ANALYSIS
The DNA is amplified using the optimized polymerase chain reaction (PCR) setup to yield a mtDNA (mitochondrial DNA) or nDNA (nuclear DNA) product. The mtDNA is analyzed to yield species identification, whereas nDNA (microsatellites) is analyzed to yield individual and gender identification.
The number of grizzly bears in the population will be estimated with mark-recapture models using DNA "fingerprints" of bears identified from hair snagging in conjunction with those identified from rub object surveys.
Field Results:
1998
|
1999
|
2000
|
|
Hair Traps: | |||
Trap Dates
|
May-Aug
|
||
# 14 day sessions
|
5
|
NA
|
5
|
# Hair Traps
|
626
|
NA
|
633
|
# Hair Samples
|
5,582
|
NA
|
5,234
|
Sign Surveys: | |||
Survey Dates
|
May-Oct
|
||
km Trail Surveyed
|
1,180
|
1,180
|
1,306
|
# Hair Samples
|
867
|
4,222
|
3,118
|
# Scat Samples
|
767
|
1,877
|
1,782
|
Genetic Results: Individual identification using nuclear DNA (7-locus microsatellite analysis) was conducted for the grizzly bear hair samples identifying 185 individual grizzly bears in 1998 and 222 in 2000. Some of the 1998 scat samples were analyzed but due to poor success analysis was not conducted on the remaining samples.
Data/Statistical Analysis: Data analysis and population modeling have been completed. The manuscript has been published.
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