| Summary: | Environmental conditions and heat waves influence blue whale foraging and reproductive effort Authors: Dawn R. Barlow 1 *, Holger Klinck 2,3 , Dimitri Ponirakis 2 , Trevor A. Branch 4 , Leigh G. Torres 1 1 Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA 2 K. Lisa Yang Center for Conservation Bioacoustics, Cornell University, Ithaca, New York, USA 3 Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA 4 School of Aquatic and Fisheries Sciences, University of Washington, Seattle, Washington, USA * dawn.barlow@oregonstate.edu Abstract Animal behavior is motivated by the fundamental need to feed and reproduce, and these behaviors can be inferred from spatiotemporal variations in biological signals such as vocalizations. Yet, linking foraging and reproductive effort to environmental drivers can be challenging for wide-ranging predator species. Blue whales are acoustically active marine predators that produce two distinct vocalizations: song and D calls. We examined environmental correlates of these vocalizations using continuous recordings from five hydrophones in the South Taranaki Bight region of New Zealand to investigate call behavior relative to ocean conditions and infer life history patterns. D calls were strongly correlated with oceanographic drivers of upwelling in spring and summer, indicating associations with foraging effort. In contrast, song displayed a highly seasonal pattern with peak intensity in fall, which aligned with the timing of conception inferred from whaling records. Finally, during a marine heatwave, reduced foraging (inferred from D calls) was followed by lower reproductive effort (inferred from song intensity).
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