Gray whales were considered specialized feeders, almost exclusively targeting benthic amphipods in the Arctic. More recent research has revealed them to be more versatile and adaptive in their feeding strategies and variety of prey. A group of a dozen individually identified gray whales return for 2-3 months each spring to feed (some for more than 25 years) in the waters of northern Puget Sound. This location is >200 km off the migration corridor for gray whales, and they began using this area in two periods (1990-91 and 1999-2000). We examined the feeding and social behavior of this group of gray whales using data from 11 deployments of suction-cup attached multi-sensor video tags in spring of 2015 and 2016. The tags gathered 132 hours of data, including the longest deployments for a suction cup tag (>67h attachment with 38h of accelerometry data and 6h of video). Video and kinematic data revealed that gray whales fed almost exclusively on intertidal ghost shrimp during high-tide periods when whales could access these areas. Typical dive depths during bottom feeding were 2.5-3 m (barely enough waters to swim) and some feeding areas were >2 km from deeper water. Semi-diurnal feeding periods ranged from < 1 h to >6h and were skewed towards the incoming period around the high tide. Gray whales spent extensive periods milling in several other areas during other periods, but the tags revealed they were not feeding. Instead they showed a high degree of social interaction, including frequent body contact with other whales, as well as sub-surface bottom resting behavior. Gray whales appear to have discovered this area during periods of food stress when they were in search of alternative prey. Despite access to foraging grounds for short periods, the nutrient-rich ghost shrimp beds appear to justify this off-migration transit and high-risk strategy.
Calambokidis, J., D. Cade, J. Fahlbusch, A. Szesciorka, A. Allen, J. Goldbogen. 2017. A high risk intertidal feeding strategy for gray whales examined with new suction-cup attached multi-sensor video tags. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.