| Summary: | Dissertation (Ph.D.) University of Alaska Fairbanks, 2023 The widespread loss of apex consumers in marine, terrestrial, and freshwater ecosystems throughout the world has precipitated profound trophic cascades and switches to different ecological states. However, conserving top predators can deliver broad biodiversity benefits and improve ecosystem resiliency. Effective conservation and management policy is predicated on a species' distribution and abundance in a given area and time. In this dissertation, I provide new insight into killer whale (Orcinus orca) distribution, vocal behavior, and abundance in the Gulf of Alaska using passive acoustic monitoring and advance long-term monitoring capacity for this species. First, I describe the year-round spatiotemporal distribution and daily acoustic residency patterns of southern Alaska resident (fish-eating) and two populations of transient (mammal-eating) killer whales. I found distinct seasonal patterns across locations for each genetically distinct population and discovered that both resident and transient killer whales used the coastal monitoring areas more extensively than previously known--including in winter. Second, I estimated resident and transient killer whale calling rates, a prerequisite to acoustic abundance estimation. I found that the mean calling rate for southern Alaska resident (fish-eating) killer whales was consistent across space, time, ambient noise level, which pod was calling, and the presence of other pods. Gulf of Alaska transient (mammal-eating) killer whale calling rates were higher than resident's and differed across locations. AT1 transients (mammal-eating) produced fewer calls more rapidly than Gulf of Alaska transients, and their mean rate was stable across spatiotemporal factors. Although transients call less often than residents, I found that once vocalizing, they do so at a higher rate. Finally, I estimated and modeled the year-round daily acoustic abundance of resident and transient killer whales across distinct areas in the ...
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