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Hildebrand L, Derville S, Hildebrand I, Torres LG. Exploring indirect effects of a classic trophic cascade between urchins and kelp on zooplankton and whales. Sci Rep 2024; 14:9815. [PMID: 38684814 PMCID: PMC11059377 DOI: 10.1038/s41598-024-59964-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 04/17/2024] [Indexed: 05/02/2024] Open
Abstract
Kelp forest trophic cascades have been extensively researched, yet indirect effects to the zooplankton prey base and gray whales have not been explored. We investigate the correlative patterns of a trophic cascade between bull kelp and purple sea urchins on gray whales and zooplankton in Oregon, USA. Using generalized additive models (GAMs), we assess (1) temporal dynamics of the four species across 8 years, and (2) possible trophic paths from urchins to kelp, kelp as habitat to zooplankton, and kelp and zooplankton to gray whales. Temporal GAMs revealed an increase in urchin coverage, with simultaneous decline in kelp condition, zooplankton abundance and gray whale foraging time. Trophic path GAMs, which tested for correlations between species, demonstrated that urchins and kelp were negatively correlated, while kelp and zooplankton were positively correlated. Gray whales showed nuanced and site-specific correlations with zooplankton in one site, and positive correlations with kelp condition in both sites. The negative correlation between the kelp-urchin trophic cascade and zooplankton resulted in a reduced prey base for gray whales. This research provides a new perspective on the vital role kelp forests may play across multiple trophic levels and interspecies linkages.
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Affiliation(s)
- Lisa Hildebrand
- Geospatial Ecology of Marine Megafauna Laboratory, Department of Fisheries, Wildlife & Conservation Sciences, Marine Mammal Institute, Oregon State University, Newport, OR, USA.
| | - Solène Derville
- Geospatial Ecology of Marine Megafauna Laboratory, Department of Fisheries, Wildlife & Conservation Sciences, Marine Mammal Institute, Oregon State University, Newport, OR, USA
- UMR ENTROPIE (IRD-Université de La Réunion-CNRS-Laboratoire d'excellence LabEx-CORAIL), Nouméa, New Caledonia
| | - Ines Hildebrand
- Geospatial Ecology of Marine Megafauna Laboratory, Department of Fisheries, Wildlife & Conservation Sciences, Marine Mammal Institute, Oregon State University, Newport, OR, USA
| | - Leigh G Torres
- Geospatial Ecology of Marine Megafauna Laboratory, Department of Fisheries, Wildlife & Conservation Sciences, Marine Mammal Institute, Oregon State University, Newport, OR, USA
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Barlow DR, Strong CS, Torres LG. Three decades of nearshore surveys reveal long-term patterns in gray whale habitat use, distribution, and abundance in the Northern California Current. Sci Rep 2024; 14:9352. [PMID: 38654001 PMCID: PMC11039675 DOI: 10.1038/s41598-024-59552-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 04/11/2024] [Indexed: 04/25/2024] Open
Abstract
The nearshore waters of the Northern California Current support an important seasonal foraging ground for Pacific Coast Feeding Group (PCFG) gray whales. We examine gray whale distribution, habitat use, and abundance over 31 years (1992-2022) using standardized nearshore (< 5 km from shore) surveys spanning a large swath of the PCFG foraging range. Specifically, we generated density surface models, which incorporate detection probability into generalized additive models to assess environmental correlates of gray whale distribution and predict abundance over time. We illustrate the importance of coastal upwelling dynamics, whereby increased upwelling only yields higher gray whale density if interspersed with relaxation events, likely because this combination optimizes influx and retention of nutrients to support recruitment and aggregation of gray whale prey. Several habitat features influence gray whale distribution, including substrate, shelf width, prominent capes, and river estuaries. However, the influence of these features differs between regions, revealing heterogeneity in habitat preferences throughout the PCFG foraging range. Predicted gray whale abundance fluctuated throughout our study period, but without clear directional trends, unlike previous abundance estimates based on mark-recapture models. This study highlights the value of long-term monitoring, shedding light on the impacts of variable environmental conditions on an iconic nearshore marine predator.
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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, OR, USA.
| | | | - Leigh G Torres
- Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, OR, USA
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Allyn EM, Scordino JJ, Akmajian AM. Distribution and demographics of mysids (Crustacea: Mysida) as prey for gray whales ( Eschrichtius robustus) in northwest Washington state. PeerJ 2024; 12:e16587. [PMID: 38239296 PMCID: PMC10795525 DOI: 10.7717/peerj.16587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 11/14/2023] [Indexed: 01/23/2024] Open
Abstract
Background The movement and distribution of gray whales (Eschrichtius robustus) during the feeding season is likely dependent on the quality of foraging opportunities and the distribution of prey species. These dynamics are especially important to understand for the Pacific Coast Feeding Group (PCFG) of gray whales which spend the feeding season along the coast from northern California, USA through northern British Columbia, Canada. In Washington state, no previous work has been done to describe available gray whale prey. The main goal of this research was to initiate studies on an important gray whale prey item in northwest Washington, mysid shrimp (Mysida), by establishing a baseline understanding of mysid swarm demographics in the area and investigating patterns in gray whale and mysid presence. Methods Prey samples were collected during June through November 2019 and June through September 2020 using a vertically-towed plankton net at seven sites in the Strait of Juan de Fuca and seven sites in the Pacific Ocean in areas where gray whales were known to feed. Mysids collected in the samples were counted and the sex, length, species, maturity, and gravidity were documented. Patterns in gray whale and mysid co-occurrence were explored through data visualization. Results Seven species of mysids were observed in the survey area. In 2019, the number of mysids per tow increased steadily through the season, the most abundant species of mysids were Holmesimysis sculpta and Neomysis rayii, and sampled mysids averaged 4.7 mm in length. In 2020, mysids were abundant in tow samples in June and July but were not abundant in the remaining months of the sampling season. The average length of mysids in 2020 was 13.3 mm, and a large portion were sexually mature males and brooded females identified as H. sculpta. Throughout the survey area, the majority of whale sightings occurred later in the season in 2019 and earlier in the season in 2020, coinciding with the trends of sampled mysids. Discussion This study provides the first description of mysid swarm composition and temporal variation in northwest Washington. Tows were dominated by a similar assemblage of mysid species as what is observed in other areas of the PCFG range. The differences in sampled mysid assemblages between years, and the presence of whales in the survey area in times and at sites where samples with high mysid counts were collected, suggest evidence for interesting predator-prey dynamics that warrant further investigation.
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Stewart JD, Joyce TW, Durban JW, Calambokidis J, Fauquier D, Fearnbach H, Grebmeier JM, Lynn M, Manizza M, Perryman WL, Tinker MT, Weller DW. Boom-bust cycles in gray whales associated with dynamic and changing Arctic conditions. Science 2023; 382:207-211. [PMID: 37824633 DOI: 10.1126/science.adi1847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 08/16/2023] [Indexed: 10/14/2023]
Abstract
Climate change is affecting a wide range of global systems, with polar ecosystems experiencing the most rapid change. Although climate impacts affect lower-trophic-level and short-lived species most directly, it is less clear how long-lived and mobile species will respond to rapid polar warming because they may have the short-term ability to accommodate ecological disruptions while adapting to new conditions. We found that the population dynamics of an iconic and highly mobile polar-associated species are tightly coupled to Arctic prey availability and access to feeding areas. When low prey biomass coincided with high ice cover, gray whales experienced major mortality events, each reducing the population by 15 to 25%. This suggests that even mobile, long-lived species are sensitive to dynamic and changing conditions as the Arctic warms.
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Affiliation(s)
- Joshua D Stewart
- Ocean Ecology Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Newport, OR, USA
| | - Trevor W Joyce
- Ocean Associates, Arlington, VA, USA
- Marine Mammal and Turtle Division, National Oceanic and Atmospheric Administration (NOAA) Southwest Fisheries Science Center, La Jolla, CA, USA
| | - John W Durban
- Marine Mammal and Turtle Division, National Oceanic and Atmospheric Administration (NOAA) Southwest Fisheries Science Center, La Jolla, CA, USA
- Sealife Response, Rehabilitation and Research (SR3), Des Moines, WA, USA
| | | | - Deborah Fauquier
- Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD, USA
| | - Holly Fearnbach
- Sealife Response, Rehabilitation and Research (SR3), Des Moines, WA, USA
| | - Jacqueline M Grebmeier
- Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, USA
| | - Morgan Lynn
- Marine Mammal and Turtle Division, National Oceanic and Atmospheric Administration (NOAA) Southwest Fisheries Science Center, La Jolla, CA, USA
| | - Manfredi Manizza
- Geosciences Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Wayne L Perryman
- Marine Mammal and Turtle Division, National Oceanic and Atmospheric Administration (NOAA) Southwest Fisheries Science Center, La Jolla, CA, USA
| | - M Tim Tinker
- Nhydra Consulting, Halifax, NS, Canada
- Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
| | - David W Weller
- Marine Mammal and Turtle Division, National Oceanic and Atmospheric Administration (NOAA) Southwest Fisheries Science Center, La Jolla, CA, USA
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Vandenberg ML, Cohen KE, Rubin RD, Goldbogen JA, Summers AP, Paig-Tran EWM, Kahane-Rapport SR. Formation of a fringe: A look inside baleen morphology using a multimodal visual approach. J Morphol 2023; 284:e21574. [PMID: 36807194 DOI: 10.1002/jmor.21574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 12/22/2022] [Accepted: 12/26/2022] [Indexed: 02/23/2023]
Abstract
Filter-feeding has been present for hundreds of millions of years, independently evolving in aquatic vertebrates' numerous times. Mysticete whales are a group of gigantic, marine filter-feeders that are defined by their fringed baleen and are divided into two groups: balaenids and rorquals. Recent studies have shown that balaenids likely feed using a self-cleaning, cross-flow filtration mechanism where food particles are collected and then swept to the esophagus for swallowing. However, it is unclear how filtering is achieved in the rorquals (Balaenopteridae). Lunging rorqual whales engulf enormous masses of both prey and water; the prey is then separated from the water through baleen plates lining the length of their upper jaw and positioned perpendicular to flow. Rorqual baleen is composed of both major (larger) and minor (smaller) keratin plates containing embedded fringe that extends into the whale's mouth, forming a filtering fringe. We used a multimodal approach, including microcomputed tomography (µCT) and scanning electron microscopy (SEM), to visualize and describe the variability in baleen anatomy across five species of rorqual whales, spanning two orders of magnitude in body length. For most morphological measurements, larger whales exhibited hypoallometry relative to body length. µCT and SEM revealed that the major and minor plates break away from the mineralized fringes at variable distances from the gums. We proposed a model for estimating the effective pore size to determine whether flow scales with body length or prey size across species. We found that pore size is likely not a proxy for prey size but instead, may reflect changes in resistance through the filter that affect fluid flow.
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Affiliation(s)
- Megan L Vandenberg
- Department of Biology, University of Washington, Seattle, Washington, USA
- Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
| | - Karly E Cohen
- Department of Biology, University of Washington, Seattle, Washington, USA
- Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
| | | | - Jeremy A Goldbogen
- Hopkins Marine Station, Stanford University, Pacific Grove, California, USA
| | - Adam P Summers
- Department of Biology, University of Washington, Seattle, Washington, USA
- Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
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Barlow DR, Klinck H, Ponirakis D, Branch TA, Torres LG. Environmental conditions and marine heatwaves influence blue whale foraging and reproductive effort. Ecol Evol 2023; 13:e9770. [PMID: 36861024 PMCID: PMC9968652 DOI: 10.1002/ece3.9770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 01/08/2023] [Accepted: 01/10/2023] [Indexed: 03/01/2023] Open
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 Aotearoa 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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Affiliation(s)
- Dawn R. Barlow
- Geospatial Ecology of Marine Megafauna Lab, Department of Fisheries, Wildlife, and Conservation Sciences, Marine Mammal InstituteOregon State UniversityNewportOregonUSA
| | - Holger Klinck
- K. Lisa Yang Center for Conservation BioacousticsCornell UniversityIthacaNew YorkUSA,Department of Fisheries, Wildlife, and Conservation Sciences, Marine Mammal InstituteOregon State UniversityNewportOregonUSA
| | - Dimitri Ponirakis
- K. Lisa Yang Center for Conservation BioacousticsCornell UniversityIthacaNew YorkUSA
| | - Trevor A. Branch
- School of Aquatic and Fisheries SciencesUniversity of WashingtonSeattleWashingtonUSA
| | - Leigh G. Torres
- Geospatial Ecology of Marine Megafauna Lab, Department of Fisheries, Wildlife, and Conservation Sciences, Marine Mammal InstituteOregon State UniversityNewportOregonUSA
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Lemos LS, Haxel JH, Olsen A, Burnett JD, Smith A, Chandler TE, Nieukirk SL, Larson SE, Hunt KE, Torres LG. Effects of vessel traffic and ocean noise on gray whale stress hormones. Sci Rep 2022; 12:18580. [PMID: 36329054 PMCID: PMC9633705 DOI: 10.1038/s41598-022-14510-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 06/08/2022] [Indexed: 11/06/2022] Open
Abstract
Human use of marinescapes is rapidly increasing, especially in populated nearshore regions where recreational vessel traffic can be dense. Marine animals can have a physiological response to such elevated human activity that can impact individual health and population dynamics. To understand the physiological impacts of vessel traffic on baleen whales, we investigated the adrenal stress response of gray whales (Eschrichtius robustus) to variable vessel traffic levels through an assessment of fecal glucocorticoid metabolite (fGC) concentrations. This analysis was conducted at the individual level, at multiple temporal scales (1-7 days), and accounted for factors that may confound fGC: sex, age, nutritional status, and reproductive state. Data were collected in Oregon, USA, from June to October of 2016-2018. Results indicate significant correlations between fGC, month, and vessel counts from the day prior to fecal sample collection. Furthermore, we show a significant positive correlation between vessel traffic and underwater ambient noise levels, which indicates that noise produced by vessel traffic may be a causal factor for the increased fGC. This study increases knowledge of gray whale physiological response to vessel traffic and may inform management decisions regarding regulations of vessel traffic activities and thresholds near critical whale habitats.
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Affiliation(s)
- Leila S. Lemos
- grid.4391.f0000 0001 2112 1969Geospatial Ecology of Marine Megafauna Lab, Department of Fisheries, Wildlife, and Conservation Science, Marine Mammal Institute, Oregon State University, 2030 SE Marine Science Dr, Newport, OR 97365 USA ,grid.65456.340000 0001 2110 1845Institute of Environment, College of Arts, Science & Education, Florida International University, 3000 NE 151st St, North Miami, FL 33181 USA
| | - Joseph H. Haxel
- grid.451303.00000 0001 2218 3491Pacific Northwest National Laboratory, 1529 W Sequim Bay Rd, Sequim, WA 98382 USA ,grid.4391.f0000 0001 2112 1969Cooperative Institute for Marine Resources Studies, Oregon State University, 2030 SE Marine Science Dr, Newport, OR 97365 USA
| | - Amy Olsen
- grid.427422.50000 0000 9883 4476Conservation Programs and Partnerships, Seattle Aquarium, 1483 Alaskan Way Pier 59, Seattle, WA 98101 USA
| | - Jonathan D. Burnett
- grid.4391.f0000 0001 2112 1969Aerial Information Systems Laboratory, Forest Engineering, Resources and Management Department, Oregon State University, Oregon, USA
| | - Angela Smith
- grid.427422.50000 0000 9883 4476Conservation Programs and Partnerships, Seattle Aquarium, 1483 Alaskan Way Pier 59, Seattle, WA 98101 USA
| | - Todd E. Chandler
- grid.4391.f0000 0001 2112 1969Geospatial Ecology of Marine Megafauna Lab, Department of Fisheries, Wildlife, and Conservation Science, Marine Mammal Institute, Oregon State University, 2030 SE Marine Science Dr, Newport, OR 97365 USA
| | - Sharon L. Nieukirk
- grid.451303.00000 0001 2218 3491Pacific Northwest National Laboratory, 1529 W Sequim Bay Rd, Sequim, WA 98382 USA
| | - Shawn E. Larson
- grid.427422.50000 0000 9883 4476Conservation Programs and Partnerships, Seattle Aquarium, 1483 Alaskan Way Pier 59, Seattle, WA 98101 USA
| | - Kathleen E. Hunt
- grid.22448.380000 0004 1936 8032Department of Biology, Smithsonian-Mason School of Conservation, George Mason University, Fairfax, VA USA
| | - Leigh G. Torres
- grid.4391.f0000 0001 2112 1969Geospatial Ecology of Marine Megafauna Lab, Department of Fisheries, Wildlife, and Conservation Science, Marine Mammal Institute, Oregon State University, 2030 SE Marine Science Dr, Newport, OR 97365 USA
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Gailey G, Zykov M, Sychenko O, Rutenko A, Blanchard AL, Aerts L, Melton RH. Gray whale density during seismic surveys near their Sakhalin feeding ground. ENVIRONMENTAL MONITORING AND ASSESSMENT 2022; 194:739. [PMID: 36255495 PMCID: PMC9579086 DOI: 10.1007/s10661-022-10025-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 04/04/2022] [Indexed: 05/31/2023]
Abstract
Oil and gas development off northeastern Sakhalin Island, Russia, has exposed the western gray whale population on their summer-fall foraging grounds to a range of anthropogenic activities, such as pile driving, dredging, pipeline installation, and seismic surveys. In 2015, the number of seismic surveys within a feeding season surpassed the level of the number and duration of previous seismic survey activities known to have occurred close to the gray whales' feeding ground, with the potential to cause disturbance to their feeding activity. To examine the extent that gray whales were potentially avoiding areas when exposed to seismic and vessel sounds, shore-based teams monitored the abundance and distribution of gray whales from 13 stations that encompassed the known nearshore feeding area. Gray whale density was examined in relation to natural (spatial, temporal, and prey energy) and anthropogenic (cumulative sound exposure from vessel and seismic sounds) explanatory variables using Generalized Additive Models (GAM). Distance from shore, water depth, date, and northing explained a significant amount of variation in gray whale densities. Prey energy from crustaceans, specifically amphipods, isopods, and cumaceans also significantly influenced gray whale densities in the nearshore feeding area. Increasing cumulative exposure to vessel and seismic sounds resulted in both a short- and longer-term decline in gray whale density in an area. This study provides further insights about western gray whale responses to anthropogenic activity in proximity to and within the nearshore feeding area. As the frequency of seismic surveys and other non-oil and gas anthropogenic activity are expected to increase off Sakhalin Island, it is critical to continue to monitor and assess potential impacts on this endangered population of gray whales.
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Affiliation(s)
- Glenn Gailey
- Cetacean EcoSystem Research, Olympia, WA, 98512, USA.
| | - Mikhail Zykov
- JASCO Applied Sciences Ltd, Dartmouth, NS, B3B 1Z1, Canada
| | - Olga Sychenko
- Cetacean EcoSystem Research, Olympia, WA, 98512, USA
| | - Alexander Rutenko
- Far East Branch of Russian Academy of Sciences, V.I. Il'ichev Pacific Oceanological Institute, Vladivostok, 690041, Russia
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A Multi-Dimensional Examination of Foraging Habitat Use by Gray Whales Using Long Time-Series and Acoustics Data. Animals (Basel) 2022; 12:ani12202735. [PMID: 36290121 PMCID: PMC9597834 DOI: 10.3390/ani12202735] [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: 09/16/2022] [Revised: 10/01/2022] [Accepted: 10/07/2022] [Indexed: 11/05/2022] Open
Abstract
Simple Summary Long term data on the number and location of foraging gray whales on the west coast of Vancouver was used to understand the rate of return and residency time of whales to certain areas. From this data, areas of increased use by foraging whales were determined, and patterns in the way the areas were used by the whales were seen. Whale location data showed them using prey patches and moving to other patches to allow the first to recover, before then returning to feed on them again later in the summer. Calves that follow their mother in their first migration were likely to return to the same site in the years after weaning. This suggests a maternal aspect to the use of foraging areas. Little is known about how whales detect prey; the use of acoustics was considered here, with call types differing between times when prey was more abundant and whales were feeding in close proximity, to those when foraging whales were more distant to each other. This suggests there may be a social aspect to the calling by gray whales in foraging areas. Abstract Gray whales (Eschrichtius robustus) show high site fidelity to feeding and breeding areas. The whales’ annual cycle could be learned or be driven by factors such as prey abundance or ocean conditions. Long-term line transect and photo-identification data were analyzed to consider intra- and inter- annual patterns of habitat use and the underlying drivers for foraging areas in Clayoquot Sound, British Columbia. Time series, autocorrelation and weighted means analysis were used on the 20-years of data (1997–2016). A generalized additive model showed that whale use of the area was most strongly influenced by the maximum number of whales, and the date of its occurrence, recorded the previous year. This maximum, when it occurred in the summer, impacted the whale numbers for up to four subsequent years. The annual average number of whales per transect also influenced the proportion of whales known to return in multiple years to forage. Many of these returning whales first used the site to wean and returned in subsequent years to feed. The transect data was also used to contextualize passive acoustic recordings, comparing call type and rate for periods when the whale number, location and social context was known. Calling patterns appeared to be socially derived, with shorter-range knock calls dominant when whales were closer, and lower-frequency moans when foraging occurred when whales were more distant from each other. This suggests that prey-finding and site use may also be influenced by conspecifics.
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Johnston DR, Rayment W, Dawson SM. Morphometrics and body condition of southern right whales on the calving grounds at Port Ross, Auckland Islands. Mamm Biol 2022. [DOI: 10.1007/s42991-021-00175-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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