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Geology topics

Steven C. Amstrup

Publications and source records attributed to Steven C. Amstrup.

78 records · Page 5Linked to original sources
USGS1989

Performance and utility of satellite telemetry during field studies of free-ranging polar bears in Alaska

Satellite telemetry technology has been used during field studies of polar bears in Alaska since 1985. A total of 109 Platform Transmitter Terminals (PTT) have been deployed on free-ranging female polar bears that seasonally inhabit waters adjacent to the Alaskan coast. The PTTs transmitted locational and sensor data to TIROS-N polar-orbiting satellites during a duty cycle of 12 hours on/60 hours off in 1985, 1986, and 1987. Expected battery life was 13.8 months, and collars were normally removed and replaced with new or refurbished PTTs at 11-13 month intervals. Duty cycles were altered to 7-8 hours on/64-65 hours off in 1988 to prolong expected battery life to 19-21 months. Sensor data transmitted included PTT internal temperature, short term activity counts recorded at 60 second intervals, and long term activity counts for the preceding 24 or 72-hour period. Early failures of PTTs to fix location (less than 75% of expected battery life) were as high as 53% during 198501986. Subsequent improvements in battery design, including better shock insulation, improved electronic, and an improved battery system have reduced early failures to 27% in 1987-1988. The harsh environment and the degree of abuse observed in recovered collars indicate that an unavoidable failure rate of 8-10% is inherent within 60 days after deployment on polar bears. A total of 18,000 locations and 201,000 sensor messages were received from female polar bears between May 1985 and June 1988. Polar bears that were marked in Alaskan waters have been located as far south as 60°N 168°W, and as far east as 70°N 127°W in the Beaufort Sea. Polar bears in the Beaufort Sea are shared with Canada, while polar bears in the Chukchi and Bering seas are shared with the Soviet Union. The international ranges of the two hypothesized populations have been documented. Satellite telemetry has detailed the large movement patterns of polar bear over these vast areas that were previously not available using other techniques.

Alaska↗
USGS1986

Research on polar bears in Alaska, 1983-1985

Research on the ecology and status of polar bear populations in Alaska has continued since 1967. Research was a joint U.S. Fish and Wildlife Service/Alaska Department of Fish and Game effort until passage of the Marine Mammal Protection Act in 1972, and has been largely a Federal effort since then. In 1985, Alaskan polar beer research continues to be carried out by the Research Division of the U.S. Fish and Wildlife Service (DOI). A recent reorganization removed authority for ecological research in Alaska from the Denver Wildlife Research Center, and vested it with the newly created Alaska Office of Fish and Wildlife Research. This new research office is the center for Federal fish and Wildlife related research throughout the state of Alaska and in its coastal waters. Although the responsibility for polar bear research lies with the U.S. Fish and Wildlife Service, numerous other organizations and agencies deserve mention for their cooperation and support of the ongoing research. These include: the U.S. National Oceanic and Atmospheric Administration (DOC), The U.S. Minerals Management Service (DOI), The Canadian Wildlife Service, The Northwest Territories Wildlife Service, the Yukon Wildlife Service, Dome Petroleum Ltd, Gulf Canada, and the Alaska Department of Fish and game.

Alaska↗
USGS1986

Polar Bear

No abstract available.

Audubon Wildlife Report↗
USGS1985

Research on Alaskan polar bears in 1979 and 1980

In 1979 the U.S. Fish and Wildlife Service continued its program of mark and recapture. From 31 March to 4 May field crews working at Point Barrow, Alaska, captured and marked a total of 15 polar bears (Table I). The small number was due to very poor ice conditions off the coast of Alaska, making tracking and capturing difficult. Four of the bears were recaptures from previous years. In addition, as part of a multi-national program (Canada, U.S., Norway) satellite transmitters were attached to 3 adult female polar bears in the hopes of tracking them to their dens the following winter. However, due to mechanical and operational difficulties, very little information was acquired in the Alaskan sector of the project.

Alaska↗