Using acoustic tags to investigate sound exposure and effects on behavior in endangered killer whales (Orcinus orca)

Abstract

In this investigation, acoustic tags (DTAGs) allow us to better understand noise exposure and potential behavioral effects in endangered Southern Resident killer whales (SRKWs). Designated critical habit of SRKWs includes summer foraging areas where vessel traffic from commercial shipping, whale-watching, and other boating activities is common. Risk factors of population recovery include vessel and noise effects, and prey quality and availability. DTAGs, equipped with hydrophones and other sensors, are attached to individual whales to collect data on vocal and movement behavior, as well as their acoustic environment. Specific research goals include: (1) quantifying received noise levels in biologically relevant frequency ranges from tag data; (2) determining relationships between noise levels and detailed vessel variables obtained from precise geo-referenced vessel data collected concurrently; (3) investigating whale acoustic and movement behavior during different activities, including foraging, to understand sound use and behavior in specific biological and environmental contexts; and (4) determining potential effects of vessels and associated noise on behavior. This paper will describe the experimental approach taken, challenges faced, and results obtained from over 80 h of tag data. These data have been critical for addressing our research goals related to multiple population risk factors of endangered SRKWs.