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Estimation of walrus populations on sea ice with infrared imagery and aerial photography

Marine Mammal Science

By:
, ,
DOI: 10.1111/j.1748-7692.2007.00169.x

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Abstract

Population sizes of ice-associated pinnipeds have often been estimated with visual or photographic aerial surveys, but these methods require relatively slow speeds and low altitudes, limiting the area they can cover. Recent developments in infrared imagery and its integration with digital photography could allow substantially larger areas to be surveyed and more accurate enumeration of individuals, thereby solving major problems with previous survey methods. We conducted a trial survey in April 2003 to estimate the number of Pacific walruses (Odobenus rosmarus divergens) hauled out on sea ice around St. Lawrence Island, Alaska. The survey used high altitude infrared imagery to detect groups of walruses on strip transects. Low altitude digital photography was used to determine the number of walruses in a sample of detected groups and calibrate the infrared imagery for estimating the total number of walruses. We propose a survey design incorporating this approach with satellite radio telemetry to estimate the proportion of the population in the water and additional low-level flights to estimate the proportion of the hauled-out population in groups too small to be detected in the infrared imagery. We believe that this approach offers the potential for obtaining reliable population estimates for walruses and other ice-associated pinnipeds. ?? 2007 by the Society for Marine Mammalogy.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Estimation of walrus populations on sea ice with infrared imagery and aerial photography
Series title:
Marine Mammal Science
DOI:
10.1111/j.1748-7692.2007.00169.x
Volume
24
Issue:
1
Year Published:
2008
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Marine Mammal Science
First page:
57
Last page:
70
Number of Pages:
14