.png)
GMU 13 Brown Bear Density and Abundance Study
Understanding brown bear density and distribution within GMU 13 is essential for responsible wildlife stewardship, community safety, and informed harvest management. Through non-invasive genetic sampling and collaboration with partners, AITRC is completing analysis of brown bear density, abundance, and habitat relationships in GMU 13.
Funded by Bureau of Indian Affairs in partnership with Alaska Department of Fish & Game and Univeristy of Alaska Fairbanks
“Why would we sell permits for bear-baiting when we don’t know how many bears are on the land?”
This project began with a powerful question from an Ahtna Elder. That question sparked a multi-year collaborative effort to improve estimates of brown bear density and abundance within GMU 13. In 2020, 2021, and 2022, the Ahtna Intertribal Resource Commission (AITRC) partnered with the Alaska Department of Fish & Game (ADFG), Ahtna Inc., and the University of Alaska Fairbanks (UAF) to conduct a substantial non-invasive genetic study of brown bears in GMU 13.
Brown bear populations are difficult and expensive to estimate. Advancements in genetic testing provide AITRC the opportunity to identify individual bears to the species level using hair samples collected from hair snares and samples saved from hunter-harvested bears. These genetic detections are being analyzed with spatially explicit capture–recapture (SECR) models to estimate brown bear density and abundance.
Where is GMU 13?
Game Management Unit (GMU) are geographic areas used by the Alaska Department of Fish and Game to organize wildlife management across Alaska. The state is divided into numbered GMUs, which help define areas for wildlife research, population monitoring, hunting regulations, and management decisions.
Game Management Unit (GMU) 13 is located in Southcentral Alaska and encompasses much of the Upper Copper River Basin, including areas surrounding Glennallen, Gulkana, Paxson, and portions of the Denali Highway. The unit is divided into five subunits (13A–13E) and includes diverse habitats ranging from forested lowlands and river valleys to alpine tundra and mountainous terrain.
Hair Snare Deployment.
The project used a clustered, non-invasive hair-snare design to study brown bears within GMU 13. Sampling efforts are clustered across the landscape, spacing of clusters and hair traps was based on the average home range of collared adult female brown bears from another ADF&G bear project.
Standard corral-style barbed wire hair snares were deployed to collect hair samples when adequate trees were in the area of interest. Barbed wire is strung around trees or posts so that tufts of hair are collected as bears pass over or under the wire to access nonfood scent attractants placed at the site. No food reward was provided; behavioral differences in detection still require consideration during analysis. In areas where no adequate trees exist, researchers built free-standing hair snares by hauling in precut spruce poles to erect structures to attach barbed wire to. Hair was collected and labeled separately by barb or collection point, with laboratory testing used to identify individuals when DNA quality permitted. GPS coordinates are recorded at each snare site, and locations for mapping and analysis.
Hair snares were deployed during separate sampling periods over the course of the summer, occurring in May, June, July, and August. Each sampling period lasts two weeks, and sites were rebaited and/or moved every two weeks. Each new sampling period, the scents and lures were changed to ensure that if bears were in the area, they would continue to investigate the “new” sites.
Why Use Genetic Sampling?
Counting bears across a large, forested landscape is challenging. Dense vegetation can make aerial surveys difficult, while bears naturally range across large areas and can be difficult to observe.
Instead of relying only on visual observations or physically capturing bears, this research used non-invasive genetic sampling during the field phase. Hair collected from snares contains DNA that can be analyzed to identify individual bears without needing to capture or handle the animal.
Where DNA quality permits, genetic analysis can distinguish species, determine sex, and establish an individual bear genotype. When the same genetic profile appears in samples collected at different locations or times, researchers know that the same individual bear has been detected again. Those detections can then be used to help estimate bear abundance and density.
Field Monitoring & Site Investigations.
Hair-snare locations were recorded using GPS and mapped in GIS software. Camera traps were deployed at select sites to monitor bear movement patterns and reactions to the hair snare design. Technicians navigate remote terrain to check sites and collect samples safely and consistently. Hunter observations and harvest records can provide complementary ecological context, but their role in any formal density model must be clearly specified.
Pairing Genetics with Trail Camera Photos.
Hair samples tell researchers which individual bears are present, while trail camera photos provide another look at how bears are using the landscape. Cameras placed near sampling locations can document bear activity and provide visual observations that complement the genetic information collected from hair snares.
By pairing DNA results with trail camera photos, researchers can build a more complete picture of bear presence and activity. Genetic samples can distinguish individual bears, species, and sex, while camera images can provide additional context about when bears visit an area and how they interact with sampling sites.
Motion-sensor cameras at selected hair-snare locations were used to document bear activity and sampling-site interactions.
Why this matters?
Estimating brown bear density and abundance is an important component of understanding the broader ecosystem in which bears function as apex predators. Reliable population estimates can provide context for evaluating predator-prey relationships, particularly in relation to concerns about low moose numbers within the region. Without accurate estimates of bear abundance and density, wildlife management decisions are made with a limited understanding of population structure and distribution.
The information gathered through this project helps address existing data gaps between the State of Alaska and the National Park Service bear population datasets. Increasing the availability of region-specific data strengthens management decisions and improves coordination among agencies and landowners operating within the Upper Copper River Basin.
Habitat Analysis and Project Status. With collaborating researchers, AITRC is evaluating how habitat features, vegetation, access routes, and other landscape factors relate to brown bear distribution and estimated density through SECR and resource-selection approaches. Field sampling has been completed; model refinement, interpretation, and scientific reporting remain underway. Final outputs and any public estimates should be released after review and agreement among project collaborators.
For Ahtna communities, abundance and density estimates can help inform discussions of public safety and responsible harvest management. Evaluating sustainable harvest opportunities require these estimates alongside additional demographic, harvest, and ecological information.
Luke Porter and Petros Platis, 2021-22 wildlife technicians, flew into Tazlina Lake where they boated around setting up sites for the Bear Hair Snare project
.jpg)
Damien James, 2022 wildlife technician, is hard at work recording all of our data for our bear project!
.jpg)
Jessy John, 2021 wildlife technician, setting up a freestanding bear hair trap to collect samples for genetic analysis
Project Leads: Kelsey Stanbro & Sterling Spilinek | Questions on this project?