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1. Multi-year profiles of T3 are positively correlated with corticosterone in male bowhead whale baleen

   https://doi.org/10.1016/j.ygcen.2025.114800  

   Hudson, Justine M; Hunt, Kathleen; Marcoux, Marianne; Buck, C Loren; Matthews, Cory (August 2025, General and comparative endocrinology)

   Thyroid hormones play an important role in the regulation of growth, development, metabolism, thermoregulation, and migration. Very little information exists on patterns of thyroid hormone concentrations in healthy mysticete whales, as many studies have focused on ill, entangled, or stranded whales, making it difficult to interpret thyroid hormone trends. In this study, we used a unique sample-set of bowhead whale baleen plates to explore the long-term interrelationships between triiodothyronine (T3), the most biologically active thyroid hormone, corticosterone, testosterone, and nitrogen isotope ratios (δ15N) (proxies for stress, reproduction, and diet, respectively) to investigate the role T3 may play in the physiology of healthy cetaceans. Baleen plates were collected between 1998 and 2011 from eight subsistence-harvested male bowhead whales across the Eastern Canadian Arctic. Each baleen plate generated 88–158 serial samples, representing ~11–22 years of life for each individual whale. T3 concentrations ranged from 0.61 to 21.62 ng/g and varied seasonally in just two whales. Most whales showed no correlation between T3 and seasonal fluctuations in testosterone or δ15N, suggesting that variation in T3 is not driven by seasonal shifts in reproductive cycles, consumer trophic level, or migration. However, a strong positive correlation between T3 and corticosterone was observed in every whale, which we hypothesized was due to non-seasonal factors that simultaneously increase metabolic rate and physiological stress. The positive correlation between T3 with corticosterone suggests that in mysticete whales, some stressors may require increased energetic output. 

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2. Historical baleen plates indicate that once abundant Antarctic blue and fin whales demonstrated distinct migratory and foraging strategies

   https://doi.org/10.1002/ece3.11376  

   Smith, Malia_E_K; Ososky, John_J; Hunt, Kathleen_E; Cioffi, William_R; Read, Andy_J; Friedlaender, Ari_S; McCarthy, Matt; Fleming, Alyson_H (May 2024, Ecology and Evolution)

   Abstract Southern hemisphere blue (Balaenoptera musculus intermedia) and fin (Balaenoptera physalus) whales are the largest predators in the Southern Ocean, with similarities in morphology and distribution. Yet, understanding of their life history and foraging is limited due to current low abundances and limited ecological data. To address these gaps, historic Antarctic blue (n = 5) and fin (n = 5) whale baleen plates, collected in 1947–1948 and recently rediscovered in the Smithsonian National Museum of Natural History, were analyzed for bulk (δ¹³C and δ¹⁵N) stable isotopes. Regular oscillations in isotopic ratios, interpreted as annual cycles, revealed that baleen plates contain approximately 6 years (14.35 ± 1.20 cm year⁻¹) of life history data in blue whales and 4 years (16.52 ± 1.86 cm year⁻¹) in fin whales. Isotopic results suggest that: (1) while in the Southern Ocean, blue and fin whales likely fed at the same trophic level but demonstrated niche differentiation; (2) fin whales appear to have had more regular annual migrations; and (3) fin whales may have migrated to ecologically distinct sub‐Antarctic waters annually while some blue whales may have resided year‐round in the Southern Ocean. These results reveal differences in ecological niche and life history strategies between Antarctic blue and fin whales during a time period when their populations were more abundant than today, and before major human‐driven climatic changes occurred in the Southern Ocean. 

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3. Sea ice directs changes in bowhead whale phenology through the Bering Strait

   https://doi.org/10.1186/s40462-023-00374-5  

   Szesciorka, Angela_R; Stafford, Kathleen_M (February 2023, Movement Ecology)

   Abstract BackgroundClimate change is warming the Arctic faster than the rest of the planet. Shifts in whale migration timing have been linked to climate change in temperate and sub-Arctic regions, and evidence suggests Bering–Chukchi–Beaufort (BCB) bowhead whales (Balaena mysticetus) might be overwintering in the Canadian Beaufort Sea. MethodsWe used an 11-year timeseries (spanning 2009–2021) of BCB bowhead whale presence in the southern Chukchi Sea (inferred from passive acoustic monitoring) to explore relationships between migration timing and sea ice in the Chukchi and Bering Seas. ResultsFall southward migration into the Bering Strait was delayed in years with less mean October Chukchi Sea ice area and earlier in years with greater sea ice area (p = 0.04, r² = 0.40). Greater mean October–December Bering Sea ice area resulted in longer absences between whales migrating south in the fall and north in the spring (p < 0.01, r² = 0.85). A stepwise shift after 2012–2013 shows some whales are remaining in southern Chukchi Sea rather than moving through the Bering Strait and into the northwestern Bering Sea for the winter. Spring northward migration into the southern Chukchi Sea was earlier in years with less mean January–March Chukchi Sea ice area and delayed in years with greater sea ice area (p < 0.01, r² = 0.82). ConclusionsAs sea ice continues to decline, northward spring-time migration could shift earlier or more bowhead whales may overwinter at summer feeding grounds. Changes to bowhead whale migration could increase the overlap with ships and impact Indigenous communities that rely on bowhead whales for nutritional and cultural subsistence. 

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4. First description of migratory behavior of humpback whales from an Antarctic feeding ground to a tropical calving ground

   https://doi.org/10.1186/s40317-021-00266-8  

   Modest, Michelle; Irvine, Ladd; Andrews-Goff, Virginia; Gough, William; Johnston, David; Nowacek, Douglas; Pallin, Logan; Read, Andrew; Moore, Reny Tyson; Friedlaender, Ari (October 2021, Animal Biotelemetry)

   Abstract BackgroundDespite exhibiting one of the longest migrations in the world, half of the humpback whale migratory cycle has remained unexamined. Until now, no study has provided a continuous description of humpback whale migratory behavior from a feeding ground to a calving ground. We present new information on satellite-derived offshore migratory movements of 16 Breeding Stock G humpback whales from Antarctic feeding grounds to South American calving grounds. Satellite locations were used to demonstrate migratory corridors, while the impact of departure date on migration speed was assessed using a linear regression. A Bayesian hierarchical state–space animal movement model (HSSM) was utilized to investigate the presence of Area Restricted Search (ARS) en route. Results35,642 Argos locations from 16 tagged whales from 2012 to 2017 were collected. The 16 whales were tracked for a mean of 38.5 days of migration (range 10–151 days). The length of individually derived tracks ranged from 645 to 6381 km. Humpbacks were widely dispersed geographically during the initial and middle stages of their migration, but convened in two convergence regions near the southernmost point of Chile as well as Peru’s Illescas Peninsula. The state–space model showed almost no instances of ARS along the migratory route. The linear regression assessing whether departure date affected migration speed showed suggestive but inconclusive support for a positive trend between the two variables. Results suggestive of stratification by sex and reproductive status were found for departure date and route choice. ConclusionsThis multi-year study sets a baseline against which the effects of climate change on humpback whales can be studied across years and conditions and provides an excellent starting point for the investigation into humpback whale migration. 

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5. Seasonally Variable Aquifer Discharge and Cooler Climate in Bermuda During the Last Interglacial Revealed by Subannual Clumped Isotope Analysis

   https://doi.org/10.1029/2020PA004145  

   Zhang, Jade Z.; Petersen, Sierra V.; Winkelstern, Ian Z.; Lohmann, Kyger C. (May 2021, Paleoceanography and Paleoclimatology)

   Abstract Faunal analog reconstructions suggest that Last Interglacial (MIS 5e) sea surface temperatures were cooler around Bermuda and in the Caribbean than modern climate. Here we describe new and revised clumped isotope measurements ofCittarium picafossil shells supporting previous findings of cooler than modern temperatures in Bermuda during the Last Interglacial. We resolve temperature and δ¹⁸O_wdifferences between two closely located and apparently coeval sites described in Winkelstern et al. (2017),https://doi.org/10.1002/2016pa003014through reprocessing raw isotopic data with the updated Brand/IUPAC parameters. New subannual‐resolution clumped isotope data reveal large variations in δ¹⁸O_wout of phase with seasonal temperature changes (i.e., lower δ¹⁸O_wvalues in winter). Supported by modern δ¹⁸O_wmeasurements identifying similar processes occurring today, we suggest past variations in coastal δ¹⁸O_wwere driven by seasonally variable freshwater discharge from a subterranean aquifer beneath the island. Taken together, our results emphasize the importance of δ¹⁸O_win controlling carbonate δ¹⁸O, and suggest that typical assumptions of constant δ¹⁸O_wshould be made cautiously in nearshore settings and can contribute to less accurate reconstructions of paleotemperature. 

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