Application of Airborne Thermal Imagery to Surveys of Pacific Walrus

We conducted tests of airborne thermal imagery of Pacific walrus to determine if this technology can be used to detect walrus groups on sea ice and estimate the number of walruses present in each group. In April 2002 we collected thermal imagery of 37 walrus groups in the Bering Sea at spatial resol...

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Bibliographic Details
Published inWildlife Society bulletin Vol. 34; no. 1; pp. 51 - 58
Main Authors BURN, DOUGLAS M, WEBBER, MARC A, UDEVITZ, MARK S
Format Journal Article
LanguageEnglish
Published Oxford, UK Blackwell Publishing Ltd 01.03.2006
The Wildlife Society
Subjects
Aerial photography
Aircraft
Altitude
Biotelemetry
Digital photography
Effectiveness studies
Fish
Ice
Marine
Marine mammals
Odobenus rosmarus
Odobenus rosmarus divergens
Pacific walrus
Pixels
Population Monitoring Techniques
Remote sensing
Sensors
Spatial resolution
thermal imagery
Wildlife management
Wildlife observation
INE, Bering Sea
Bering Sea
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Summary:We conducted tests of airborne thermal imagery of Pacific walrus to determine if this technology can be used to detect walrus groups on sea ice and estimate the number of walruses present in each group. In April 2002 we collected thermal imagery of 37 walrus groups in the Bering Sea at spatial resolutions ranging from 1–4 m. We also collected high-resolution digital aerial photographs of the same groups. Walruses were considerably warmer than the background environment of ice, snow, and seawater and were easily detected in thermal imagery. We found a significant linear relation between walrus group size and the amount of heat measured by the thermal sensor at all 4 spatial resolutions tested. This relation can be used in a double-sampling framework to estimate total walrus numbers from a thermal survey of a sample of units within an area and photographs from a subsample of the thermally detected groups. Previous methods used in visual aerial surveys of Pacific walrus have sampled only a small percentage of available habitat, resulting in population estimates with low precision. Results of this study indicate that an aerial survey using a thermal sensor can cover as much as 4 times the area per hour of flight time with greater reliability than visual observation.
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E‐mail
has a B.A. and an M.A. in biology with an emphasis on marine biology from San Francisco State University. He joined the United States Fish and Wildlife Service in 1992 and served as a Refuge Manager in Hawaii and later in California. From 2000–2005 he was a Wildlife Biologist in the Pacific walrus program of the Marine Mammals Management Office in Alaska. He is currently the Refuge Manager of the Muscatatuck National Wildlife Refuge in Indiana.
Marc A. Webber
is a wildlife biologist with the United States Fish and Wildlife Service, Marine Mammals Management Office in Anchorage, Alaska. He received a B.S. in wildlife biology form the University of Maine and an M.S. in biological oceanography from the University of Miami. His work in Alaska includes studies of Pacific walrus, sea otters, and polar bears. His current professional interests include the application of remote sensing to marine mammal studies, and the conservation of sea otters in southwest Alaska.
Mark S. Udevitz
Douglas M. Burn
is a Research Statistician with the United States Geological Survey, Alaska Science Center in Anchorage, Alaska. He earned B.S. and M.S. degrees in wildlife biology and management at Colorado State University and West Virginia University, and a Ph.D. in biomathematics and statistics at North Carolina State University. His research focuses on methods for sampling, estimating demographic parameters, and modeling dynamics of wildlife populations.
douglas_burn@fws.gov
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ISSN:0091-7648
1938-5463
DOI:10.2193/0091-7648(2006)34[51:AOATIT]2.0.CO;2