Gulf of Alaska | Mammals DOCTORATE POSTER PRESENTATION How much do killer whales call? Quantifying calling rates for passive acoustic density estimation Presenter: Hannah Myers , hmyers8@alaska.edu, University of Alaska Fairbanks Killer whales ( Orcinus orca ) are top predators in the North Pacific Ocean and are divided into three genetically and acoustically distinct ecotypes: resident (fish-eating), transient (mammal-eating), and offshore (largely shark-eating). Previous research has demonstrated high use and strong seasonal patterns of resident and transient killer whale presence in coastal areas of the northern Gulf of Alaska. However, moving beyond presence to acoustic density estimation requires an estimate of the rate of call production per animal. In this study, we take advantage of the unique social structure and dialect use of resident killer whales to estimate the calling rate of the southern Alaska residents, a fish-eating population of approximately 1,000 killer whales. The resident killer whale calling rate was highly stable at 0.77 calls/whale/min (95% confidence interval 0.72 to 0.82 calls/whale/min) and was not influenced by the pod recorded, season, time of day, location, or presence of other killer whale groups. We estimate mammal-eating transient killer whale calling rates by pairing passive acoustic recordings with a long-term vessel survey record. The transient calling rate was an order of magnitude lower than that of residents, and similarly was not influenced by spatiotemporal factors. These results show that calling rate will be a reliable multiplier to estimate the number of animals present in passive acoustic recordings, thereby enabling year-round density estimation of killer whales across multiple locations in the northern Gulf of Alaska. This will provide unprecedented insight into the top-down forcing effects and inform management of this federally protected species. Estimating calling rates using a large passive acoustic dataset also generated novel insights into killer whale communication. Dan Olsen , waterdogdan@gmail.com, North Gulf Oceanic Society Craig Matkin , comatkin@gmail.com, North Gulf Oceanic Society Brenda Konar , bhkonar@alaska.edu, University of Alaska Fairbanks
Alaska Marine Science Symposium 2023 255
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