Animal-Borne Metrics Enable Acoustic Detection of Blue Whale Migration

Abstract

Linking individual and population scales is fundamental to many concepts in ecology [1Levin S.A. The problem of pattern and scale in ecology.Ecology. 1992; 73: 1943-1967Crossref Scopus (4853) Google Scholar], including migration [2Torney C.J. Hopcraft J.G.C. Morrison T.A. Couzin I.D. Levin S.A. From single steps to mass migration: the problem of scale in the movement ecology of the Serengeti wildebeest.Philos. Trans. R. Soc. Lond. B Biol. Sci. 2018; 373: 20170012Crossref PubMed Scopus (29) Google Scholar, 3Couzin I.D. Collective animal migration.Curr. Biol. 2018; 28: R976-R980Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar]. This behavior is a critical [4Alerstam T. Hedenström A. Åkesson S. Long-distance migration: Evolution and determinants.Oikos. 2003; 103: 247-260Crossref Scopus (784) Google Scholar] yet increasingly threatened [5Tucker M.A. Böhning-Gaese K. Fagan W.F. Fryxell J.M. Van Moorter B. Alberts S.C. Ali A.H. Allen A.M. Attias N. Avgar T. et al.Moving in the Anthropocene: Global reductions in terrestrial mammalian movements.Science. 2018; 359: 466-469Crossref PubMed Scopus (487) Google Scholar] part of the life history of diverse organisms. Research on migratory behavior is constrained by observational scale [2Torney C.J. Hopcraft J.G.C. Morrison T.A. Couzin I.D. Levin S.A. From single steps to mass migration: the problem of scale in the movement ecology of the Serengeti wildebeest.Philos. Trans. R. Soc. Lond. B Biol. Sci. 2018; 373: 20170012Crossref PubMed Scopus (29) Google Scholar], limiting ecological understanding and precise management of migratory populations in expansive, inaccessible marine ecosystems [6Hays G.C. Ferreira L.C. Sequeira A.M.M. Meekan M.G. Duarte C.M. Bailey H. Bailleul F. Bowen W.D. Caley M.J. Costa D.P. et al.Key Questions in Marine Megafauna Movement Ecology.Trends Ecol. Evol. 2016; 31: 463-475Abstract Full Text Full Text PDF PubMed Scopus (305) Google Scholar]. This knowledge gap is magnified for dispersed oceanic predators such as endangered blue whales (Balaenoptera musculus). As capital breeders, blue whales migrate vast distances annually between foraging and breeding grounds, and their population fitness depends on synchrony of migration with phenology of prey populations [7Pirotta E. Mangel M. Costa D.P. Mate B. Goldbogen J.A. Palacios D.M. Hückstädt L.A. McHuron E.A. Schwarz L. New L. A dynamic state model of migratory behavior and physiology to assess the consequences of environmental variation and anthropogenic disturbance on marine vertebrates.Am. Nat. 2018; 191: E40-E56Crossref PubMed Scopus (42) Google Scholar, 8Abrahms B. Hazen E.L. Aikens E.O. Savoca M.S. Goldbogen J.A. Bograd S.J. Jacox M.G. Irvine L.M. Palacios D.M. Mate B.R. Memory and resource tracking drive blue whale migrations.Proc. Natl. Acad. Sci. USA. 2019; 116: 5582-5587Crossref PubMed Scopus (93) Google Scholar]. Despite previous studies of individual-level blue whale vocal behavior via bio-logging [9Lewis L.A. Calambokidis J. Stimpert A.K. Fahlbusch J. Friedlaender A.S. McKenna M.F. Mesnick S.L. Oleson E.M. Southall B.L. Szesciorka A.R. Širović A. Context-dependent variability in blue whale acoustic behaviour.R. Soc. Open Sci. 2018; 5: 180241Crossref PubMed Scopus (29) Google Scholar, 10Oleson E.M. Calambokidis J. Burgess W.C. McDonald M.A. LeDuc C.A. Hildebrand J.A. Behavioral context of call production by eastern North Pacific blue whales.Mar. Ecol. Prog. Ser. 2007; 330: 269-284Crossref Scopus (189) Google Scholar] and population-level acoustic presence via passive acoustic monitoring [11Szesciorka A.R. Ballance L.T. Širović A. Rice A. Ohman M.D. Hildebrand J.A. Franks P.J.S. Timing is everything: Drivers of interannual variability in blue whale migration.Sci. Rep. 2020; 10: 7710Crossref PubMed Scopus (25) Google Scholar], detection of the life history transition from foraging to migration remains challenging. Here, we integrate direct high-resolution measures of individual behavior and continuous broad-scale acoustic monitoring of regional song production (Figure 1A) to identify an acoustic signature of the transition from foraging to migration in the Northeast Pacific population. We find that foraging blue whales sing primarily at night, whereas migratory whales sing primarily during the day. The ability to acoustically detect population-level transitions in behavior provides a tool to more comprehensively study the life history, fitness, and plasticity of population behavior in a dispersed, capital breeding population. Real-time detection of this behavioral signal can also inform dynamic management efforts [12Oestreich, W.K., Chapman, M.S., and Crowder, L.B. A comparative analysis of dynamic management in marine and terrestrial systems. Front. Ecol. Environ. 10.1002/fee.2243.Google Scholar] to mitigate anthropogenic threats to this endangered population [13Redfern J.V. McKenna M.F. Moore T.J. Calambokidis J. Deangelis M.L. Becker E.A. Barlow J. Forney K.A. Fiedler P.C. Chivers S.J. Assessing the risk of ships striking large whales in marine spatial planning.Conserv. Biol. 2013; 27: 292-302Crossref PubMed Scopus (121) Google Scholar, 14Goldbogen J.A. Southall B.L. DeRuiter S.L. Calambokidis J. Friedlaender A.S. Hazen E.L. Falcone E.A. Schorr G.S. Douglas A. Moretti D.J. et al.Blue whales respond to simulated mid-frequency military sonar.Proc. Biol. Sci. 2013; 280: 20130657PubMed Google Scholar]).

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