Investigating acoustics, behavior and vessel noise exposure in endangered killer whales (Orcinus orca) using digital acoustic recording tags.

Abstract

Southern resident killer whales (SRKWs) are a fish-eating, endangered population that frequents the inland waters of Washington and British Columbia. Several risk factors have been identified that could hinder population recovery, including prey quantity and/or quality and disturbance by vessel presence and/or noise. There is a well-developed whale watching industry in the area, with an average of about 20 vessels viewing SRKWs during summer daylight hours. In some studies, killer whales decreased foraging behavior with vessel presence but details about noise exposure and prey capture events were lacking. Other research has characterized how vessel traffic increased background noise levels in SRKW habitat but data on how such exposure varies in a diving killer whale were also lacking. Our current research involves using suction cup attached digital acoustic recording tags (DTAGs) equipped with hydrophones and dive sensors on SRKWs to better characterize their use of sound, particularly during foraging, and to quantify vessel noise received at the whale. Data on vessel type and behavior and whale behavior, as well as prey samples, are also collected concurrently. This paper will describe the experimental approach taken and some preliminary results assessing risk factors potentially affecting the recovery of SRKWs.