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Ferreira LC, Jenner C, Jenner M, Udyawer V, Radford B, Davenport A, Moller L, Andrews-Goff V, Double M, Thums M. Predicting suitable habitats for foraging and migration in Eastern Indian Ocean pygmy blue whales from satellite tracking data. MOVEMENT ECOLOGY 2024; 12:42. [PMID: 38845039 PMCID: PMC11157879 DOI: 10.1186/s40462-024-00481-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 05/21/2024] [Indexed: 06/09/2024]
Abstract
BACKGROUND Accurate predictions of animal occurrence in time and space are crucial for informing and implementing science-based management strategies for threatened species. METHODS We compiled known, available satellite tracking data for pygmy blue whales in the Eastern Indian Ocean (n = 38), applied movement models to define low (foraging and reproduction) and high (migratory) move persistence underlying location estimates and matched these with environmental data. We then used machine learning models to identify the relationship between whale occurrence and environment, and predict foraging and migration habitat suitability in Australia and Southeast Asia. RESULTS Our model predictions were validated by producing spatially varying accuracy metrics. We identified the shelf off the Bonney Coast, Great Australian Bight, and southern Western Australia as well as the slope off the Western Australian coast as suitable habitat for migration, with predicted foraging/reproduction suitable habitat in Southeast Asia region occurring on slope and in deep ocean waters. Suitable foraging habitat occurred primarily on slope and shelf break throughout most of Australia, with use of the continental shelf also occurring, predominanly in South West and Southern Australia. Depth of the water column (bathymetry) was consistently a top predictor of suitable habitat for most regions, however, dynamic environmental variables (sea surface temperature, surface height anomaly) influenced the probability of whale occurrence. CONCLUSIONS Our results indicate suitable habitat is related to dynamic, localised oceanic processes that may occur at fine temporal scales or seasonally. An increase in the sample size of tagged whales is required to move towards developing more dynamic distribution models at seasonal and monthly temporal scales. Our validation metrics also indicated areas where further data collection is needed to improve model accuracy. This is of particular importance for pygmy blue whale management, since threats (e.g., shipping, underwater noise and artificial structures) from the offshore energy and shipping industries will persist or may increase with the onset of an offshore renewable energy sector in Australia.
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Affiliation(s)
- Luciana C Ferreira
- Australian Institute of Marine Science, Indian Ocean Marine Research Centre, University of Western Australia, Crawley, WA, Australia.
| | - Curt Jenner
- Centre for Whale Research (WA) Inc., Fremantle, WA, Australia
| | | | - Vinay Udyawer
- Australian Institute of Marine Science, Indian Ocean Marine Research Centre, University of Western Australia, Crawley, WA, Australia
| | - Ben Radford
- Australian Institute of Marine Science, Indian Ocean Marine Research Centre, University of Western Australia, Crawley, WA, Australia
| | - Andrew Davenport
- Centre for Whale Research (WA) Inc., Fremantle, WA, Australia
- Centre for Marine Science and Technology, Curtin University, Bentley, WA, Australia
| | - Luciana Moller
- Cetacean Ecology, Behaviour and Evolution Lab, College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Virginia Andrews-Goff
- Australian Antarctic Division, Department of Climate Change, Energy, the Environment and Water, Kingston, TAS, Australia
| | - Mike Double
- Australian Antarctic Division, Department of Climate Change, Energy, the Environment and Water, Kingston, TAS, Australia
| | - Michele Thums
- Australian Institute of Marine Science, Indian Ocean Marine Research Centre, University of Western Australia, Crawley, WA, Australia
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2
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Barlow DR, Klinck H, Ponirakis D, Holt Colberg M, Torres LG. Temporal occurrence of three blue whale populations in New Zealand waters from passive acoustic monitoring. J Mammal 2022. [DOI: 10.1093/jmammal/gyac106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Abstract
Describing spatial and temporal occurrence patterns of wild animal populations is important for understanding their evolutionary trajectories, population connectivity, and ecological niche specialization, with relevance for effective management. Throughout the world, blue whales produce stereotyped songs that enable identification of separate acoustic populations. We harnessed continuous acoustic recordings from five hydrophones deployed in the South Taranaki Bight (STB) region of Aotearoa New Zealand from January 2016 to February 2018. We examined hourly presence of songs from three different blue whale populations to investigate their contrasting ecological use of New Zealand waters. The New Zealand song was detected year-round with a seasonal cycle in intensity (peak February–July), demonstrating the importance of the region to the New Zealand population as both a foraging ground and potential breeding area. The Antarctic song was present in two distinct peaks each year (June–July; September–October) and predominantly at the offshore recording locations, suggesting northbound and southbound migration between feeding and wintering grounds. The Australian song was only detected during a 10-day period in January 2017, implying a rare vagrant occurrence. We therefore infer that the STB region is the primary niche of the New Zealand population, a migratory corridor for the Antarctic population, and outside the typical range of the Australian population.
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Affiliation(s)
- Dawn R Barlow
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University , Newport, Oregon 97365 , USA
| | - Holger Klinck
- K. Lisa Yang Center for Conservation Bioacoustics, Cornell University , Ithaca, New York 14850 , USA
- Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University , Newport, Oregon 97365 , USA
| | - Dimitri Ponirakis
- K. Lisa Yang Center for Conservation Bioacoustics, Cornell University , Ithaca, New York 14850 , USA
| | - Mattea Holt Colberg
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University , Newport, Oregon 97365 , USA
- Department of Integrative Biology, Oregon State University , Corvallis, Oregon 97331 , USA
| | - Leigh G Torres
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University , Newport, Oregon 97365 , USA
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3
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Ryan JP, Benoit‐Bird KJ, Oestreich WK, Leary P, Smith KB, Waluk CM, Cade DE, Fahlbusch JA, Southall BL, Joseph JE, Margolina T, Calambokidis J, DeVogelaere A, Goldbogen JA. Oceanic giants dance to atmospheric rhythms: Ephemeral wind-driven resource tracking by blue whales. Ecol Lett 2022; 25:2435-2447. [PMID: 36197736 PMCID: PMC9827854 DOI: 10.1111/ele.14116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 08/04/2022] [Accepted: 08/14/2022] [Indexed: 01/12/2023]
Abstract
Trophic transfer of energy through marine food webs is strongly influenced by prey aggregation and its exploitation by predators. Rapid aggregation of some marine fish and crustacean forage species during wind-driven coastal upwelling has recently been discovered, motivating the hypothesis that predators of these forage species track the upwelling circulation in which prey aggregation occurs. We examine this hypothesis in the central California Current Ecosystem using integrative observations of upwelling dynamics, forage species' aggregation, and blue whale movement. Directional origins of blue whale calls repeatedly tracked upwelling plume circulation when wind-driven upwelling intensified and aggregation of forage species was heightened. Our findings illustrate a resource tracking strategy by which blue whales may maximize energy gain amid ephemeral foraging opportunities. These findings have implications for the ecology and conservation of diverse predators that are sustained by forage populations whose behaviour is responsive to episodic environmental dynamics.
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Affiliation(s)
- John P. Ryan
- Monterey Bay Aquarium Research InstituteMoss LandingCaliforniaUSA
| | | | - William K. Oestreich
- Monterey Bay Aquarium Research InstituteMoss LandingCaliforniaUSA,Hopkins Marine StationStanford UniversityStanfordCaliforniaUSA
| | - Paul Leary
- Naval Postgraduate SchoolMontereyCaliforniaUSA
| | | | - Chad M. Waluk
- Monterey Bay Aquarium Research InstituteMoss LandingCaliforniaUSA
| | - David E. Cade
- Hopkins Marine StationStanford UniversityStanfordCaliforniaUSA
| | - James A. Fahlbusch
- Hopkins Marine StationStanford UniversityStanfordCaliforniaUSA,Cascadia Research CollectiveOlympiaWashingtonUSA
| | - Brandon L. Southall
- Southall Environmental Associates, Inc.AptosCaliforniaUSA,University of CaliforniaSanta CruzCaliforniaUSA
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4
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Lambert C, Authier M, Blanchard A, Dorémus G, Laran S, Van Canneyt O, Spitz J. Delayed response to environmental conditions and infra-seasonal dynamics of the short-beaked common dolphin distribution. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220379. [PMID: 36465685 PMCID: PMC9709568 DOI: 10.1098/rsos.220379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 11/06/2022] [Indexed: 06/17/2023]
Abstract
Cetaceans adjust their distribution and abundance to encountered conditions across years and seasons, but we poorly understand such small-scale changes for many species, especially in winter. Crucial challenges confront some populations during this season, such as the high levels of fisheries-induced mortality faced by the common dolphin (Delphinus delphis) in the Northeast Atlantic shelves. For such species, understanding the winter fine-scale dynamics is crucial. We aimed to identify the dolphin distribution drivers during the winters of 2020 and 2021, with a focus on determining the lag between changes in oceanographic conditions and dolphin distribution. The changes were related to temporal delays specific to the nature and cascading effects that oceanographic processes had on the trophic chain. By determining the most important conditions and lags to dolphin distributions, we shed light on the poorly understood intrusions of dolphins within coastal waters during winter: they displayed a strong preference for the coastal-shelf waters front and extensively followed its spatial variations, with their overall densities increasing over the period and peaking in March-April. The results presented here provide invaluable information on the winter distribution dynamics and should inform management decisions to help reduce the unsustainable mortalities of this species in the by-catch of fisheries.
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Affiliation(s)
- C. Lambert
- Observatoire Pelagis UAR 3462 CNRS-LRUniv, 5 allée de l’Océan, La Rochelle 17000, France
- Centre d’Etudes Biologiques de Chizé UMR 7372 CNRS-LRUniv, 405 Rte de Prissé la Charrière, Villiers-en-bois 79360, France
- Littoral ENvironnement et Sociétés UMR 7266 CNRs-LRUniv, 2 Rue Olympe de Gouge, La Rochelle 17000, France
| | - M. Authier
- Observatoire Pelagis UAR 3462 CNRS-LRUniv, 5 allée de l’Océan, La Rochelle 17000, France
| | - A. Blanchard
- Observatoire Pelagis UAR 3462 CNRS-LRUniv, 5 allée de l’Océan, La Rochelle 17000, France
| | - G. Dorémus
- Observatoire Pelagis UAR 3462 CNRS-LRUniv, 5 allée de l’Océan, La Rochelle 17000, France
| | - S. Laran
- Observatoire Pelagis UAR 3462 CNRS-LRUniv, 5 allée de l’Océan, La Rochelle 17000, France
| | - O. Van Canneyt
- Observatoire Pelagis UAR 3462 CNRS-LRUniv, 5 allée de l’Océan, La Rochelle 17000, France
| | - J. Spitz
- Observatoire Pelagis UAR 3462 CNRS-LRUniv, 5 allée de l’Océan, La Rochelle 17000, France
- Centre d’Etudes Biologiques de Chizé UMR 7372 CNRS-LRUniv, 405 Rte de Prissé la Charrière, Villiers-en-bois 79360, France
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5
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Barlow DR, Estrada Jorge M, Klinck H, Torres LG. Shaken, not stirred: blue whales show no acoustic response to earthquake events. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220242. [PMID: 35845856 PMCID: PMC9277279 DOI: 10.1098/rsos.220242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
Quantifying how animals respond to disturbance events bears relevance for understanding consequences to population health. We investigate whether blue whales respond acoustically to naturally occurring episodic noise by examining calling before and after earthquakes (27 040 calls, 32 earthquakes; 27 January-29 June 2016). Two vocalization types were evaluated: New Zealand blue whale song and downswept vocalizations ('D calls'). Blue whales did not alter the number of D calls, D call received level or song intensity following earthquakes (paired t-tests, p > 0.7 for all). Linear models accounting for earthquake strength and proximity revealed significant relationships between change in calling activity surrounding earthquakes and prior calling activity (D calls: R 2 = 0.277, p < 0.0001; song: R 2 = 0.080, p = 0.028); however, these same relationships were true for 'null' periods without earthquakes (D calls: R 2 = 0.262, p < 0.0001; song: R 2 = 0.149, p = 0.0002), indicating that the pattern is driven by blue whale calling context regardless of earthquake presence. Our findings that blue whales do not respond to episodic natural noise provide context for interpreting documented acoustic responses to anthropogenic noise sources, including shipping traffic and petroleum development, indicating that they potentially evolved tolerance for natural noise sources but not novel noise from anthropogenic origins.
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Affiliation(s)
- Dawn R. Barlow
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, and Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA
| | - Mateo Estrada Jorge
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, and Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA
- Department of Computer Science and Department of Physics, Oregon State University, Corvallis, Oregon, USA
| | - Holger Klinck
- K. Lisa Yang Center for Conservation Bioacoustics, Cornell University, Ithaca, New York, USA
- Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA
| | - Leigh G. Torres
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, and Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA
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6
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Bedriñana-Romano L, Zarate PM, Hucke-Gaete R, Viddi FA, Buchan SJ, Cari I, Clavijo L, Bello R, Zerbini AN. Abundance and distribution patterns of cetaceans and their overlap with vessel traffic in the Humboldt Current Ecosystem, Chile. Sci Rep 2022; 12:10639. [PMID: 35739207 PMCID: PMC9226171 DOI: 10.1038/s41598-022-14465-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 06/07/2022] [Indexed: 11/30/2022] Open
Abstract
The Humboldt Current Ecosystem (HCE) is one of the most productive marine ecosystems, sustaining one of the largest fishing industries in the world. Although several species of cetaceans are known to inhabit these productive waters, quantitative assessments of their abundance and distribution patterns are scarce and patchy. Here, we present the first abundance and distribution estimates for fin whale (Balaenoptera physalus), southeast Pacific blue whales (Balaenoptera musculus), sperm whale (Physeter macrocephalus), dusky dolphin (Lagenorhynchus obscurus), and common dolphin (Delphinus spp.) in the entire Chilean portion of the HCE. Line transect surveys were conducted during 2016–2021 between 18° S and 41° S and up to ~ 200 km offshore, and data were analyzed using distance sampling methods. Group counts were modelled as a function of environmental variables using single step Bayesian Binomial N-mixture model (BNMM), which allows full uncertainty propagation between model components. By using spatially explicit predictions of cetacean densities and observed vessel densities in the HCE, we provide quantitative assessments on the relative probability of cetaceans encountering vessels (RPCEV). Dusky dolphin and fin whale showed the largest distribution overlap with industrial and artisanal fishery fleets. Our results highlight areas where effort should be prioritized to address the extant but unquantified negative interactions between vessels and cetaceans in Chilean HCE.
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Affiliation(s)
- Luis Bedriñana-Romano
- Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile. .,NGO Centro Ballena Azul, 5090000, Valdivia, Chile. .,Centro de Investigación Oceanográfica COPAS Coastal, Universidad de Concepción, 4070043, Concepción, Región del Bio Bio, Chile.
| | - Patricia M Zarate
- Instituto de Fomento Pesquero, Departamento de Oceanografía y Medio Ambiente, Almirante Manuel Blanco Encalada 839, Valparaíso, Chile.,MigraMar, 2099 Westshore Rd, CA, 94923, Bodega Bay, USA
| | - Rodrigo Hucke-Gaete
- Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.,NGO Centro Ballena Azul, 5090000, Valdivia, Chile.,Centro de Investigación Oceanográfica COPAS Coastal, Universidad de Concepción, 4070043, Concepción, Región del Bio Bio, Chile
| | - Francisco A Viddi
- Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.,NGO Centro Ballena Azul, 5090000, Valdivia, Chile
| | - Susannah J Buchan
- Centro de Investigación Oceanográfica COPAS Coastal, Universidad de Concepción, 4070043, Concepción, Región del Bio Bio, Chile.,Centro de Investigación Oceanográfica COPAS Sur-Austral, Universidad de Concepción, 4070043, Concepción, Región del Bio, Chile.,Centro de Estudios Avanzados en Zonas Áridas, Raúl Bitran 1305, 1700000, La Serena, Región del Coquimbo, Chile
| | - Ilia Cari
- Instituto de Fomento Pesquero, Departamento de Oceanografía y Medio Ambiente, Almirante Manuel Blanco Encalada 839, Valparaíso, Chile
| | - Ljubitza Clavijo
- Instituto de Fomento Pesquero, Departamento de Oceanografía y Medio Ambiente, Almirante Manuel Blanco Encalada 839, Valparaíso, Chile
| | - Robert Bello
- Instituto de Fomento Pesquero, Departamento de Oceanografía y Medio Ambiente, Almirante Manuel Blanco Encalada 839, Valparaíso, Chile
| | - Alexandre N Zerbini
- Cooperative Institute for Climate, Ocean and Ecosystem Studies, University of Washington & Marine Mammal Laboratory Alaska Fisheries Science Center/NOAA, 7600 Sand Point Way NE, Seattle, WA, USA.,Marine Ecology and Telemetry Research, 2468 Camp McKenzie Tr NW, Seabeck, WA, 98380, USA.,Instituto Aqualie, Av. Dr. Paulo Japiassú Coelho, 714, Sala 206, Juiz de Fora, MG, 36033-310, Brazil
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7
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Rice A, Širović A, Hildebrand JA, Wood M, Carbaugh-Rutland A, Baumann-Pickering S. Update on frequency decline of Northeast Pacific blue whale (Balaenoptera musculus) calls. PLoS One 2022; 17:e0266469. [PMID: 35363831 PMCID: PMC8975115 DOI: 10.1371/journal.pone.0266469] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 03/21/2022] [Indexed: 12/31/2022] Open
Abstract
Worldwide, the frequency (pitch) of blue whale (Balaenoptera musculus) calls has been decreasing since first recorded in the 1960s. This frequency decline occurs over annual and inter-annual timescales and has recently been documented in other baleen whale species, yet it remains unexplained. In the Northeast Pacific, blue whales produce two calls, or units, that, when regularly repeated, are referred to as song: A and B calls. In this population, frequency decline has thus far only been examined in B calls. In this work, passive acoustic data collected in the Southern California Bight from 2006 to 2019 were examined to determine if A calls are also declining in frequency and whether the call pulse rate was similarly impacted. Additionally, frequency measurements were made for B calls to determine whether the rate of frequency decline is the same as was calculated when this phenomenon was first reported in 2009. We found that A calls decreased at a rate of 0.32 Hz yr-1 during this period and that B calls were still decreasing, albeit at a slower rate (0.27 Hz yr-1) than reported previously. The A call pulse rate also declined over the course of the study, at a rate of 0.006 pulses/s yr-1. With this updated information, we consider the various theories that have been proposed to explain frequency decline in blue whales. We conclude that no current theory adequately accounts for all aspects of this phenomenon and consider the role that individual perception of song frequency may play. To understand the cause behind call frequency decline, future studies might want to explore the function of these songs and the mechanism for their synchronization. The ubiquitous nature of the frequency shift phenomenon may indicate a consistent level of vocal plasticity and fine auditory processing abilities across baleen whale species.
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Affiliation(s)
- Ally Rice
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, United States of America
- * E-mail:
| | - Ana Širović
- Texas A&M University at Galveston, Galveston, TX, United States of America
| | - John A. Hildebrand
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, United States of America
| | - Megan Wood
- Texas A&M University at Galveston, Galveston, TX, United States of America
| | | | - Simone Baumann-Pickering
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, United States of America
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8
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Oestreich WK, Abrahms B, McKenna MF, Goldbogen JA, Crowder LB, Ryan JP. Acoustic signature reveals blue whales tune life history transitions to oceanographic conditions. Funct Ecol 2022. [DOI: 10.1111/1365-2435.14013] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- William K. Oestreich
- Hopkins Marine Station Department of Biology Stanford University Pacific Grove CA USA
| | - Briana Abrahms
- Center for Ecosystem Sentinels Department of Biology University of Washington Seattle WA USA
| | - Megan F. McKenna
- Hopkins Marine Station Department of Biology Stanford University Pacific Grove CA USA
| | - Jeremy A. Goldbogen
- Hopkins Marine Station Department of Biology Stanford University Pacific Grove CA USA
| | - Larry B. Crowder
- Hopkins Marine Station Department of Biology Stanford University Pacific Grove CA USA
| | - John P. Ryan
- Monterey Bay Aquarium Research Institute Moss Landing CA USA
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9
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Social exploitation of extensive, ephemeral, environmentally controlled prey patches by supergroups of rorqual whales. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2021.09.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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10
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Incorporating Geographical Scale and Multiple Environmental Factors to Delineate the Breeding Distribution of Sea Turtles. DRONES 2021. [DOI: 10.3390/drones5040142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Temperature is often used to infer how climate influences wildlife distributions; yet, other parameters also contribute, separately and combined, with effects varying across geographical scales. Here, we used an unoccupied aircraft system to explore how environmental parameters affect the regional distribution of the terrestrial and marine breeding habitats of threatened loggerhead sea turtles (Caretta caretta). Surveys spanned four years and ~620 km coastline of western Greece, encompassing low (<10 nests/km) to high (100–500 nests/km) density nesting areas. We recorded 2395 tracks left by turtles on beaches and 1928 turtles occupying waters adjacent to these beaches. Variation in beach track and inwater turtle densities was explained by temperature, offshore prevailing wind, and physical marine and terrestrial factors combined. The highest beach-track densities (400 tracks/km) occurred on beaches with steep slopes and higher sand temperatures, sheltered from prevailing offshore winds. The highest inwater turtle densities (270 turtles/km) occurred over submerged sandbanks, with warmer sea temperatures associated with offshore wind. Most turtles (90%) occurred over nearshore submerged sandbanks within 10 km of beaches supporting the highest track densities, showing the strong linkage between optimal marine and terrestrial environments for breeding. Our findings demonstrate the utility of UASs in surveying marine megafauna and environmental data at large scales and the importance of integrating multiple factors in climate change models to predict species distributions.
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