Chuck Schwartz's Research Projects

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Greater Yellowstone Grizzly Bear Population Monitoring

The Interagency Grizzly Bear Study Team monitors the status and trend of the Yellowstone grizzly bear population annually. Monitoring includes:
1. Maintaining a sample of radio-collared bears through the ecosystem. We use these collared bears to estimate reproductive rates and determine survival (PDF chapters 3-6). Data from collared bears also provides information on habitat use, home range size, habitat occupied, cause specific mortality.
2. Counting the number of females with cubs-of-the-year. We use counts of females with cubs to index bear abundance. These counts are used to estimate population size against which mortality thresholds are established.
3. We use sightings of females with young to determine occupancy in the ecosystem.
4. We track conflicts and mortalities each year in an effort to determine causes and locations and aid managers.
5. We report these findings in our annual reports (PDF).

Grizzly Bear Habitat Use and Selection

The Interagency Grizzly Bear Study Team monitors the status and trend of the Yellowstone grizzly bear habitat. Monitoring includes:
1. We monitor the abundance of 4 major foods each year. These include cutthroat trout abundance in tributary streams of Yellowstone Lake, carcass abundance on winter range, counts of whitebark pine cones, and use of cutworm moth sites.
2. We maintain a sample of radio-collared bears that we track to determine seasonal movements, habitat use, home range, and dispersal. We also collar bears with Global Positioning System telemetry collars that provide 2-4 locations for each bear each day. This information is used to determine how bears select for specific resources within the ecosystem
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Grizzly Bear Use of Yellowstone Cutthroat Trout

We began a new research program in spring of 2007 to investigate the use of cutthroat trout by grizzly and black bears on Yellowstone Lake. The project is using wire snags to collect hair samples from bears in the vicinity of spawning streams. DNA analysis of these hair samples will help us determine how many individual bear use fish and the sex of those bears. Mercury (PDF) analysis will be used on the hair to determine fish consumption rates. In addition, we are collaring a small number of individuals to learn more about their movements and food habits. To do this, we are using a new type of telemetry collar. These collars collect location information for each individual at 30-180 minute intervals. The collars are also equipped with a communication system that allows us to remotely retrieve data once per week. Field crews then visit these locations in an effort to determine the activity and foods consumed by each bear. The Yellowstone Lake cutthroat trout has been declining because of the illegal introduction of lake trout. Information from this study will be compared to information for a similar study conducted about 10 years ago (PDF).

Use of stable isotopes and mercury to determine diets of bears

Stable isotopes (PDF) allow biologists to determine the proportions of plants and meat in diets of animals. Mercury (PDF) allows us to determine fish consumption rates. These methods are being used to monitor diets of black and grizzly bears in the Greater Yellowstone Ecosystem. This project will analyze all samples collected from grizzly bears since 1997. We will also analyze samples collected from a sample of black bears from both Yellowstone and Grand Teton National Parks.

Impact of humans on grizzly bear survival in the Greater Yellowstone

Humans are the single greatest cause of grizzly bear mortality in the Greater Yellowstone Ecosystem. In an earlier analysis (PDF Chapter 7) we show that mortality rates are greatest outside the U.S. Fish and Wildlife Service Grizzly Bear Recovery Zone. This project focuses on what human impacts most affect bear survival. We are exploring a number of factors that might influence bear survival, including residential and recreational developments, roads, trails, camp sites, sport hunting, and the availability of bear foods. We are using a modeling approach with data from radio-collared bears in a spatially explicit manner. Our goal is to identify which factors most affect bear survival, how these factors are distributed on the landscape, and provide guidance to managers to most effectively keep habitats safe for bears.