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...

Full description

Saved in:
Bibliographic Details
Published in:Wildlife Society bulletin 2006-03, Vol.34 (1), p.51-58
Main Authors: BURN, DOUGLAS M, WEBBER, MARC A, UDEVITZ, MARK S
Format: Article
Language:English
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
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
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.
ISSN:0091-7648
1938-5463
DOI:10.2193/0091-7648(2006)34[51:AOATIT]2.0.CO;2