Satellite images provide a valuable research tool though their use in whale research has been more limited due to challenges in resolution and catching whales at the surface. We explore a novel use of Google Earth to identify gray whale feeding pits exposed at low tide. During their migration from Mexico, a small group of gray whales (typically 8-12) forage on ghost shrimp in the waters around Whidbey Island, WA for 2-3 months each spring. Many of these whales return annually to this area (some for 25 or more years) to feed on dense intertidal ghost shrimp beds that are exposed at low tide. We searched images available on Google Earth as of March 2017, for northern Puget Sound spanning from 47.8 N to 48.4 N and 122.2 W and 122.7 W and found 10 different dates with suitable low tide images from 23 May 2005 to 17 July 2015. From these we documented 19,447 identifiable feeding pits of gray whales. The highest number were seen on the Snohomish River Delta which accounted for 14,289 (73%) and were seen in 9 images spanning 5 different years from 2005 to 2015. The locations identified were consistent with observed locations gray whales were seen feeding at high tide and higher resolution images obtained from aerial flights. While it was more challenging to locate whales at the surface in the images, in three images at high tide, whales were identified in these same areas. Studying freely available satellite images can be used as a non-invasive method to investigate the spatial and temporal feeding behaviors of benthic feeding gray whales. Higher resolution and more precise temporal information would improve this approach and potentially expand the ability to detect either whales or the signs of their activities.
Harrison, N., J. Calambokidis. 2017. Google Earth satellite images provide novel method for examining feeding areas of gray whales in Puget Sound, Washington. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.Download PDF
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