GRANITE: Gray whale Response to Ambient Noise Informed by Technology and Ecology

Background
Summary

Investigators: Dr. Leigh Torres, Dr. Joe Haxel, Dr. Kathleen Hunt, Dr. Leslie New, Dr. Lisa Hildebrand, Dr. Clara Bird, Dr. KC Bierlich, Dr. Alejandro Fernández Ajó, Dr. Enrico Pirotta, Natalie Chazal, Marc Rams i Rios, Todd Chandler

Cetaceans are acoustically active, dependent on, and sensitive to the surrounding soundscape. Therefore, understanding the scales, intensities and types of impacts from ocean noise on their ecology and populations is a critical step toward improved management and protection. Studies have shown behavioral impacts on various cetacean species from acute ocean noise events, such as seismic air guns, mid-frequency sonar and elevated vessel traffic. Yet, it is unclear how chronic, elevated ambient noise levels may affect the physiology, behavior and ecology of individuals, or how these impacts may translate into biologically significant events with long-term consequences for individuals or populations (e.g., the Population Consequences of Multiple Stressors (PCoMS) model).

In 2015, the GEMM Lab initiated a multifaceted and non-invasive research project to evaluate the hormonal variability and health of gray whales that forage along the Oregon coast between May and October each year. These whales are part of the Pacific Coast Feeding Group (PCFG) and forage in the coastal habitat off Oregon, where they are exposed to variable ambient ocean noise conditions (e.g., storms, vessel traffic).

This is a large, multidisciplinary and highly collaborative project, with many inter-connected objectives: (1) measure and characterize the coastal soundscape of Oregon, (2) describe the variation in reproductive and stress hormones in gray whale fecal samples, (3) evaluate the trends in gray whale body condition and morphology by demographic unit and temporal period, (4) assess the foraging ecology and population dynamics of the PCFG relative to variation in habitat and prey availability, (5) quantify how various foraging behaviors relate to individual, habitat, and body condition, and (6) link these previously described data sets and results to evaluate the relationships between ambient ocean noise levels and gray whale health.

Throughout this project, we employ multiple innovative methods to observe and measure gray whale ecology and physiology, and ultimately assess the role of variable ocean noise on whale stress. We monitor coastal ambient ocean noise using hydrophones, assess gray whale reproductive and stress hormone levels through fecal sample collection and analysis, use drones to document whale behavior and body condition, deploy GoPro camera drops and collect zooplankton samples to describe prey availability, and deploy suction cup accelerometer tags (with video and acoustic sensors) to describe underwater whale movements and surroundings.

Findings from our project will be used to inform regulatory decisions regarding allowable noise thresholds in the vicinity of baleen whale habitats, aiding species conservation through informed management practices.

Summary of accomplishments:

Quantified gray whale foraging behavior for the first time using multi-sensor biologging, identifying distinct behavioral states and foraging tactics.
Revealed diel shifts in foraging strategy and depth, and documented bubble blasts as a behavioral adaptation for buoyancy control in shallow-water feeding.
Established how individual morphology and buoyancy shape the energetic costs of diving and foraging, and developed models to estimate daily field metabolic rate.
Demonstrated that gray whale body condition is sensitive to oceanographic variables along the Oregon Coast, such as increasing hypoxia and the ratio between upwelling and relaxation events.
Developed an AI model to automatically detect gray whales in drone videos and then extract measurements of body length and body condition that are within 5% of human measurements.
Developed a 3D printed LiDAR altimeter housing that can easily attach to commercial drones to help increase the accuracy of morphological measurements of marine mammals (gray whales!).
Identified clear seasonal patterns in male reproductive physiology using non-invasive fecal endocrinology, providing new insight into reproductive timing.
Demonstrated substantial individual variation in space use, site fidelity, and exposure to anthropogenic stressors across the PCFG population.
Highlighted age-specific differences in habitat use and risk, particularly the heightened exposure of juveniles to human activities.
Integrated multi-indicator health data to predict female calving probability and identified emerging demographic concerns (declining body size and fewer young individuals).
Developed modeling and analytical approaches that strengthen long-term monitoring capacity and improve assessment of population-level consequences of environmental and human-driven stressors.
Identified morphological differences between PCFG and ENP gray whales, showing that PCFG whales have smaller asymptotic lengths, skulls, and flukes which provides evidence of morphological adaptation to a distinct coastal foraging niche.
Demonstrated that drone-based photogrammetry (specifically body width at 50% of total length) is a reliable, non-invasive tool for diagnosing pregnancy in gray whales, improving estimates of reproductive rates.
Characterized coastal Oregon underwater soundscapes and showed that sound levels and whale vocalization patterns differ significantly over short spatial scales due to vessel activity, highlighting localized anthropogenic noise impacts.

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Publications:

Colson, K. M., Pirotta, E., New, L., Cade, D. E., Calambokidis, J., Bierlich, K. C., Bird, C. N., Fernandez Ajó, A., Hildebrand, L., Trites, A. W., and Torres, L. G. (2025). Using accelerometry tags to quantify gray whale foraging behavior. Marine Mammal Science, 41(2), e13210. https://doi.org/10.1111/mms.13210

Fernandez Ajó, A., Buck, C. L., Hunt, K. E., Pirotta, E., New, L., Dillon, D., Bierlich, K.C, Hildebrand, L., Bird, C. N., and Torres, L. G. (2025). Variation in faecal testosterone levels in male gray whales on a foraging ground relative to maturity and timing. Conservation Physiology, 13(1), coae094. https://doi.org/10.1093/conphys/coae094

Hildebrand, L., New, L., Pirotta, E., Stewart, J. D., Hildebrand, I., Newell, C., Bierlich, K. C., Bird, C. N., Fernandez Ajó, A., Turek, D., and Torres, L. G. (2025). Bayesian estimation of individual gray whale space use reveals differential exposure to stressors. Ecology and Evolution, 15(5), e71330. https://doi.org/10.1002/ece3.71330

Pirotta, E., New, L., Fernandez Ajó, A., Bierlich, K. C., Bird, C. N., Buck, C. L., Hildebrand, L., Hunt, K. E., Calambokidis, J., Torres, L. G. (2025). Body size, nutritional state and endocrine state are associated with calving probability in a long‐lived marine species. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.70068

Bird, C. N., Pirotta, E., New, L., Cornelius, J. M., Sumich, J. L., Colson, K. M., Bierlich, K. C., Hildebrand, L., Fernandez Ajó, A., Doron, A., and Torres, L. G. (2025). Size and body condition drive the energetic cost of a baleen whale foraging in shallow habitat. PeerJ, 13, e20247. https://doi.org/10.7717/peerj.20247

Bird, C. N., Pirotta, E., New, L., Bierlich, K. C., Hildebrand, L., Fernandez Ajó, A., and Torres, L. G. (2024). Bubble blasts! An adaptation for buoyancy regulation in shallow foraging gray whales. Ecology and Evolution, 14(8), e70093. https://doi.org/10.1002/ece3.70093

Bird, C. N., Pirotta, E., New, L., Bierlich, K. C., Donnelly, M., Hildebrand, L., Fernandez Ajó, A., and Torres, L. G. (2024). Growing into it: evidence of an ontogenetic shift in grey whale use of foraging tactics. Animal Behaviour, 214, 121-135. https://doi.org/10.1016/j.anbehav.2024.06.004

Bierlich, K. C., Kane, A., Hildebrand, L., Bird, C. N., Fernandez Ajo, A., Stewart, J. D., Hewitt, J., Hildebrand, I., Sumich, J., Torres, L. G. (2023). Downsized: gray whales using an alternative foraging ground have smaller morphology. Biology Letters, 19(8), 20230043. https://doi.org/10.1098/rsbl.2023.0043

Fernandez Ajó, A., Pirotta, E., Bierlich, K. C., Hildebrand, L., Bird, C. N., Hunt, K. E., Buck, C. L., Dillon, D., and Torres, L. G. (2023). Assessment of a non-invasive approach to pregnancy diagnosis in gray whales through drone-based photogrammetry and faecal hormone analysis. Royal Society Open Science, 10(7), 230452. https://doi.org/10.1098/rsos.230452

Haver, S. M., Haxel, J., Dziak, R. P., Roche, L., Matsumoto, H., Hvidsten, C., and Torres, L. G. (2023). The variable influence of anthropogenic noise on summer season coastal underwater soundscapes near a port and marine reserve. Marine Pollution Bulletin, 194, 115406. https://doi.org/10.1016/j.marpolbul.2023.115406

Pirotta, E., K.C. Bierlich, L. New, L. Hildebrand, C.N. Bird, A. Fernandez Ajó, and L.G. Torres, Modeling individual growth reveals decreasing gray whale body length and correlations with ocean climate indices at multiple scales. Global Change Biology, 2024. 30(6): p. e17366. https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.17366

Pirotta, E., A. Fernandez Ajó, K.C. Bierlich, C.N. Bird, C.L. Buck, S.M. Haver, J.H. Haxel, L. Hildebrand, K.E. Hunt, L.S. Lemos, L. New, and L.G. Torres, Assessing variation in faecal glucocorticoid concentrations in gray whales exposed to anthropogenic stressors. Conservation Physiology, 2023. 11(1). https://doi.org/10.1093/conphys/coad082

Torres, L.G., S.M. Brander, J.I. Parker, E.M. Bloom, R. Norman, J.E. Van Brocklin, K.S. Lasdin, and L. Hildebrand, Zoop to poop: assessment of microparticle loads in gray whale zooplankton prey and fecal matter reveal high daily consumption rates. Frontiers in Marine Science, 2023. 10. https://www.frontiersin.org/articles/10.3389/fmars.2023.1201078

Torres, L.G., C.N. Bird, F. Rodríguez-González, F. Christiansen, L. Bejder, L. Lemos, J. Urban R, S. Swartz, A. Willoughby, J. Hewitt, and K. Bierlich, Range-Wide Comparison of Gray Whale Body Condition Reveals Contrasting Sub-Population Health Characteristics and Vulnerability to Environmental Change. Frontiers in Marine Science, 2022. 9. https://www.frontiersin.org/article/10.3389/fmars.2022.867258

Lemos, L.S., J.H. Haxel, A. Olsen, J.D. Burnett, A. Smith, T.E. Chandler, S.L. Nieukirk, S.E. Larson, K.E. Hunt, and L.G. Torres, Effects of vessel traffic and ocean noise on gray whale stress hormones. Scientific Reports, 2022. 12(1): p. 18580. https://doi.org/10.1038/s41598-022-14510-5

Lemos, Leila S., Amy Olsen, Angela Smith, Jonathan D. Burnett, Todd E. Chandler, Shawn Larson, Kathleen E. Hunt, and Leigh G. Torres. "Stressed and slim or relaxed and chubby? A simultaneous assessment of gray whale body condition and hormone variability." Marine Mammal Science (2021). https://doi.org/10.1111/mms.12877

Lemos, Leila, Amy Olsen, Angela Smith, Todd E Chandler, Shawn Larson, Kathleen Hunt, and Leigh G Torres. "Assessment of fecal steroid and thyroid hormone metabolites in eastern North Pacific gray whales." Conservation Physiology, Volume 8, Issue 1 (2020). https://doi.org/10.1093/conphys/coaa110.

Soledade Lemos, Leila, Jonathan D. Burnett, Todd E. Chandler, James L. Sumich, and Leigh G. Torres. "Intra- and Inter-Annual Variation in Gray Whale Body Condition on a Foraging Ground." Ecosphere 11, no. 4 (2020): e03094. https://dx.doi.org/10.1002/ecs2.3094.

Torres, Leigh G., Sharon L. Nieukirk, Leila Lemos, and Todd E. Chandler. "Drone Up! Quantifying Whale Behavior from a New Perspective Improves Observational Capacity." Original Research, Frontiers in Marine Science 5, no. 319 (2018-September-10 2018). https://dx.doi.org/10.3389/fmars.2018.00319.

Supplemental material: Full compilation video of gray whale behaviors

Burnett, Jonathan D., Leila Lemos, Dawn Barlow, Michael G. Wing, Todd Chandler, and Leigh G. Torres. "Estimating Morphometric Attributes of Baleen Whales with Photogrammetry from Small Uass: A Case Study with Blue and Gray Whales." Marine Mammal Science 35, no. 1 (2019): 108-39. https://dx.doi.org/10.1111/mms.12527.

Media and videos: