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Map showing the seasonal broad distribution ranges of bowhead whales (Balaena mysticetus) in the Eastern (green) and Western Arctic (blue). Plain black arrows indicate broad northward migration (spring) and dashed black arrows broad southward migration (fall). Map after COSEWIC (2009), Dueck and Ferguson (2009), Quakenbush et al. (2013), and Harwood et al. (2017). (Color figure online)
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Previous studies have demonstrated that the analysis of biogeochemical tracers along baleen can provide seasonal, annual, and longer term insights into whale movements, habitat use, diet, and ecosystem processes. We measured the mercury (Hg) concentration and stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope compositions along baleen plates of bowhe...
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... Furthermore, several recent studies have shown relatively consistent δ 15 N values of annual cycles within baleen plates of blue whales and other mysticetes (Blevins et al., 2022;Busquets-Vass et al., 2017;Eisenmann et al., 2016;Silva et al., 2019;Trueman et al., 2019). We detrended each plate's δ 15 N values using a Gaussian low-pass filter to study seasonal trends (Park & Gambéroni, 1995;Pomerleau et al., 2018) then used Fast Fourier Transform (FFT) to calculate peak spectral frequencies to estimate annual cycles ( Figure A5). Spectral peak frequencies were converted to cm/cycle (1/frequency) for each individual, then averaged by species to calculate species growth rate (Matthews & Ferguson, 2015;Pomerleau et al., 2018). ...
... We detrended each plate's δ 15 N values using a Gaussian low-pass filter to study seasonal trends (Park & Gambéroni, 1995;Pomerleau et al., 2018) then used Fast Fourier Transform (FFT) to calculate peak spectral frequencies to estimate annual cycles ( Figure A5). Spectral peak frequencies were converted to cm/cycle (1/frequency) for each individual, then averaged by species to calculate species growth rate (Matthews & Ferguson, 2015;Pomerleau et al., 2018). Only individuals with at least three annual cycles were considered when calculating species averages (shown as ±1 standard deviation). ...
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.
... Because baleen grows continually at a generally predictable rate , and because it, like mammalian hair and nails, therefore encompasses a "snapshot" of a few years of a whale's life, baleen has proven useful in physiological research . This is even more valuable considering how well baleen (again, like other keratinous tissues) retains both endogenous and exogenous substances within a whale's body, most notably hormones, isotopes, and seawater contaminants (Caraveo-Patiño et al., 2007;Pomerleau et al., 2018). Therefore, baleen has become highly advantageous for biologists whose studies focus not on filtration but instead on endocrinological, isotopic, and toxicological or pollutant research. ...
Recent findings have greatly improved our understanding of mysticete oral filtration, and have upended the traditional view of baleen filtration as a simple process. Flow tank experiments, telemetric tag deployment on whales, and other lab and field methods continue to yield new data and ideas. These suggest that several mechanisms arose from ecological, morphological, and biomechanical adaptations facilitating the evolution of extreme body size in Mysticeti. Multiple lines of evidence strongly support a characterization of baleen filtration as a conceptually dynamic process, varying according to diverse intraoral locations and times of the filtration process, and to other prevailing conditions. We review and highlight these lines of evidence as follows. First, baleen appears to work as a complex metafilter comprising multiple components with differing properties. These include major and minor plates and eroded fringes (AKA bristles or hairs), as well as whole baleen racks. Second, it is clear that different whale species rely on varied ecological filtration modes ranging from slow skimming to high-speed lunging, with other possibilities in between. Third, baleen filtration appears to be a highly dynamic and flow-dependent process, with baleen porosity not only varying across sites within a single rack, but also by flow direction, speed, and volume. Fourth, findings indicate that baleen (particularly of balaenid whales and possibly other species) generally functions not as a simple throughput sieve, but instead likely uses cross-flow or other tangential filtration, as in many biological systems. Fifth, evidence reveals that the time course of baleen filtration, including rate of filter filling and clearing, appears to be more complex than formerly envisioned. Flow direction, and possibly plate and fringe orientation, appears to change during different stages of ram filtration and water expulsion. Sixth, baleen’s flexibility and related biomechanical properties varies by location within the whole filter (=rack), leading to varying filtration conditions and outcomes. Seventh, the means of clearing/cleaning the baleen filter, whether by hydraulic, hydrodynamic, or mechanical methods, appears to vary by species and feeding type, notably intermittent lunging versus continuous skimming. Together, these and other findings of the past two decades have greatly elucidated processes of baleen filtration, and heightened the need for further research. Many aspects of baleen filtration may pertain to other biological filters; designers can apply several aspects to artificial filtration, both to better understand natural systems and to design and manufacture more effective synthetic filters. Understanding common versus unique features of varied filtration phenomena, both biological and artificial, will continue to aid scientific and technical understanding, enable fruitful interdisciplinary partnerships, and yield new filter designs.
... Bowhead whales feed on zooplankton (e.g., calanoid copepods ;Fortune et al., 2020b,c;Pontbriand et al., 2023), primarily during late summer through autumn (e.g., Finley, 2001;Pomerleau et al., 2011Pomerleau et al., , 2012. However, stable isotope analysis and movement data from tagged whales have revealed that bowhead whales likely feed year-round, although at a lower rate in winter Matthews & Ferguson, 2015;Pomerleau et al., 2018). In autumn, ECWG bowhead whales are found along the east coast of Baffin Island, the west coast of Greenland, and Foxe Basin Reeves & Mitchell, 1990;Reeves et al., 1983). ...
Climate change poses new challenges to Arctic marine mammals, with increasing vessel traffic and associated underwater noise pollution emerging as significant threats. The bowhead whale ( Balaena mysticetus ), an endemic Arctic cetacean, faces these new threats. The Eastern Canada‐West Greenland (ECWG) bowhead whale population migrates through areas with the highest levels of vessel traffic in the Canadian Arctic. Here, we document the spatial and temporal overlap between 36 satellite‐tagged ECWG bowhead whales and vessels equipped with Automatic Identification System (AIS) transponders during 2012–2017. We report 1,145 instances where vessels were within 125 km of a tagged whale, with 306 occurrences within distances ≤50 km. Overlap between vessels and tagged bowhead whales was quantified monthly within years to investigate individual whale encounter rates. Results indicate that ECWG bowhead whales encounter the majority (79%) of vessels annually during August–October, with the highest number of encounters (42%) observed in September. Encounter rates ranged from 0.25 to 0.51 vessels encountered per day per whale during August–October compared to <0.07 vessels per day in all other months in this study. To better inform conservation strategies, further research is required to assess bowhead whale behavioral responses relative to distance from vessels.
... It is ubiquitous but unevenly distributed in marine environments globally (Liu et al., 2021;Médieu et al., 2022). On an oceanic scale, concentrations of Hg can increase on a gradient with latitude (Houssard et al., 2019), can differ within estuarine habitats (Eagles-Smith and Ackerman, 2014), and can contaminate marine wildlife populations to different extents (Carravieri et al., 2017;Pomerleau et al., 2018;Albert et al., 2021b;Médieu et al., 2022). The distribution of Hg can be influenced by water currents, which can transport Hg to new habitats, and zones of upwelling have been associated with higher concentrations of Hg in coastal habitats (Conaway et al., 2009;Cossa and Tabard, 2020). ...
... Measurements of bulk carbon (δ 13 C) and nitrogen (δ 15 N) stable isotopes in baleen has been successfully applied to assess time-integrated diet and movements of different cetacean species (e.g., Best and Schell, 1996;Pomerleau et al., 2018;Silva et al., 2019). δ 15 N values are often used as an indicator of trophic position (Fry, 1988), whereas δ 13 C values reflect the sources of primary production that fuel the food webs and are generally used to distinguish movements across isotopically distinct food webs. ...
... Previous studies on mysticetes showed correlated and non-correlated δ 15 N and δ 13 C cycles along their baleen plates (Best & Schell 1996, Caraveo-Patiño et al. 2007, Matthews & Ferguson 2015, Hunt et al. 2018, Pomerleau et al. 2018, Reiss et al. 2020. For ex ample, bowhead whales Balaena mysticetus and sei whales Balaenoptera borealis have synchronous δ 15 N and δ 13 C cycles, which indicates that they forage continuously in isotopically distinct regions throughout their distribution (Matthews & Ferguson 2015, Pomerleau et al. 2018, Reiss et al. 2020). ...
... Previous studies on mysticetes showed correlated and non-correlated δ 15 N and δ 13 C cycles along their baleen plates (Best & Schell 1996, Caraveo-Patiño et al. 2007, Matthews & Ferguson 2015, Hunt et al. 2018, Pomerleau et al. 2018, Reiss et al. 2020. For ex ample, bowhead whales Balaena mysticetus and sei whales Balaenoptera borealis have synchronous δ 15 N and δ 13 C cycles, which indicates that they forage continuously in isotopically distinct regions throughout their distribution (Matthews & Ferguson 2015, Pomerleau et al. 2018, Reiss et al. 2020). On the other hand, gray whales Eschrichtius robustus and blue whales Balaenoptera musculus showed no correlation between δ 15 N and δ 13 C (Caraveo-Patiño et al. 2007, Hunt et al. 2018. ...
Seasonal migration of the Critically Endangered North Atlantic right whale Eubalaena glacialis along the eastern seaboard of North America has been well studied. Since 2010, however, right whales have shifted their summer foraging location from the Bay of Fundy to the Gulf of St. Lawrence. There is a need to better understand right whale distribution to manage anthropogenic activities and mitigate impacts on whales. Stable isotope ratios of baleen plates can provide details about migration and foraging behaviour of an individual over a period of several years. We interpreted δ ¹³ C and δ ¹⁵ N cycles, examined whether stable isotope ratios of baleen could detect the right whale distribution shift, and compared variation within and among individuals before and after 2010. δ ¹³ C and δ ¹⁵ N values were compared between 8 right whales that died between 1992 and 2005 (pre-2010) and 5 right whales that died in 2019 (post-2010). The correlation between δ ¹³ C and δ ¹⁵ N varied considerably between individuals, indicating no clear pattern of annual migration in δ ¹³ C among whales. We observed a change in both isotope ratios after 2010, whereby the post-2010 whales were enriched in ¹³ C and ¹⁵ N relative to the pre-2010 whales (mean ± SE: 0.5 ± 0.1 and 0.9 ± 0.2‰, respectively). The isotopic variance among and within whales did not change after 2010. These results suggest that a range shift observed in sighting data is also reflected in the isotope ratios of right whale baleen. Detecting shifts in right whale migration is essential for protecting this species, and stable isotope analyses may be useful in future conservation efforts.
... Biopsy samples from bowhead whales can be used to determine the age of sampled whales using DNA methylation (Parsons et al. 2023), the sex of sampled whales (Linsky et al. 2022), pregnancy rates for sexually mature whales (Pallin et al. 2018), and their diet (Marcoux et al. 2012;Pomerleau et al. 2018). From combinations of these data and with samples from a large number of whales, the ages at sexual maturity and senescence of female bowhead whales can more accurately be determined, and the population structure can be determined as well. ...
Bowhead whales ( Balaena mysticetus ) have adopted growth and reproductive strategies to survive in a challenging environment where no other mysticete whales reside. They grow slowly, become sexually mature at around 25 years (later than other mammals), and do not give birth until they have sufficient energy reserves for the best possible chance of survival of the calf to weaning and long-term survival of the mother. To compensate for late maturity and long inter-birth intervals, some seem to have the capability to live to 200+ years of age, making them the longest-lived mammal known to date. Bowhead whale males have large testes per body size, and it is hypothesized that the basic polygynandrous system of females and males mating with multiple partners per estrous cycle allows for males to not compete violently against each other. Instead, they use sperm competition by volume of sperm for enhanced capability to father as many offspring as possible. Also, as in right whales ( Eubalaena spp.), the length of the penis is proportionally longer than those of balaenopterids. Details of sperm volume, potential variabilities of sperm viabilities, and actual paternities are unknown, but some patterns can be inferred from the closely related right whales with similar morphologies.
... To temporally match the biomarker results, we restricted dive data to the summer and fall period (June 1−November 30, as defined by Fortune et al. 2020b) following the tagging of the whales. Although bowhead whales forage year-round (Pomerleau et al. 2018), this period is when most of the foraging occurs (Fortune et al. 2020b) and, thus, is more representative of the integrated diet found in skin and blubber samples. Additionally, only dives occurring during an ARM behavioural state based on time stamps were included in the analysis, as foraging behaviour typically occurs in ARM while foraging is limited during the long uninterrupted linear movements typical of a Transit behavioural state (Fortune et al. 2020c). ...
Shifts in zooplankton quantity and quality caused by climate change could challenge the ability of bowhead whales to meet their energetic requirements. When facing such selection pressure, intra-population variation dampens the negative effects and provides population-level resilience. Previous studies observed inter-individual diet variation in bowhead whales, but the mechanism responsible for the variation was undetermined. We investigated foraging variability in Eastern Canada-West Greenland bowhead whales using dietary biomarkers (stable isotopes, fatty acids) and movement data (satellite telemetry with time-depth recorders) from the same individuals. We found that bowhead whale individuals using distinct summer and fall foraging habitats displayed differences in horizontal movements, foraging dive depth, and diet. For individuals using the Canadian Arctic Archipelago habitat (Foxe Basin, Gulf of Boothia, Prince Regent Inlet, Lancaster Sound and Admiralty Inlet, Nunavut), they performed long distance movements across regions, and their foraging dive depth was generally shallow, but increased from July to November. These whales displayed higher δ ¹³ C and δ ¹⁵ N values and ratios of C16:1n7/C16:0. Individuals using the West Baffin Bay habitat (Cumberland Sound, Baffin Bay, Davis Strait) were more localized in their horizontal movements and consistent over time in their foraging dive depth, which was generally deeper. These whales displayed lower δ ¹³ C and δ ¹⁵ N values and ratios of C16:1n7/C16:0. Overall, this inter-individual variation in diet and foraging behaviour could indicate some niche variation which would be beneficial for the population under changing habitats and prey availability.
... For example, carbon and nitrogen stable isotope measurements have been paired with measurements of reproductive and stress hormones from claws of bearded (Erignathus barbatus) and ringed (Pusa hispia) seals to understand the connection between seasonal changes in diet, reproduction, and stress (Crain et al., 2021). Longitudinal sampling of stable isotopes has been successfully paired with sampling of mercury in baleen from two populations of bowhead whales (Balaena mysticetus), which demonstrated they forage year-round, though they consume more mercury during the summer months (Pomerleau et al., 2018). ...
... However, it is yet to be determined whether bowheads will be able to adjust their energy budget by allocating more time to foraging (behavioural) or shift their distribution (dispersal) as they did during the Late Pleistocene (Foote et al., 2013) when pronounced fluctuations in environmental conditions occurred. Central to understanding the role that behavioural flexibility (i.e., plasticity) (Refsnider and Janzen, 2012;Samarra and Miller, 2015;Beever et al., 2017;Buchholz et al., 2019) may play in mitigating population level impacts of climate change is knowing to what extent bowhead whales (Reeves et al., 1983;Richardson et al., 1995;Fortune et al., 2020c) forage seasonally (Matthews and Ferguson, 2015;Pomerleau et al., 2018). ...
... Although juvenile males appear to allocate more time to feeding across seasons compared to females, this may be an artifact of an unbalanced sample size given that foraging effort for sub-adult males and females (equal sample sizes) shows close agreement, providing support of year-round foraging effort despite demography. Furthermore, wintertime feeding has been corroborated for the eastern population by longitudinal analysis of stable isotopes and mercury analysis from bowhead baleen (Matthews and Ferguson, 2015;Pomerleau et al., 2018). Behavioural evidence of year-round foraging has been detected for the western population in the Gulf of Anadyr in the Bering Sea, where whales conduct probable foraging dives to the seafloor where diapausing life-stages of copepods are anticipated to aggregate (Citta et al., 2015). ...
The ecological impact of environmental changes at high latitudes (e.g., increasing temperature, and decreased sea ice cover) on low-trophic species, such as bowhead whales, are poorly understood. Key to understanding the vulnerability of zooplanktivorous predators to climatic shifts in prey is knowing whether they can make behavioural or distributional adjustments to maintain sufficient prey acquisition rates. However, little is known about how foraging behaviour and associated environmental conditions fluctuate over space and time. We collected long-term movement (average satellite transmission days were 397 (± 204 SD) in 2012 and 484 (± 245 SD) in 2013) and dive behaviour data for 25 bowhead whales (Balaena mysticetus) equipped with time-depth telemetry tags, and used hierarchical switching-state-space models to quantify their movements and behaviours (resident and transit). We examined trends in inferred two-dimensional foraging behaviours based on dive shape of Eastern Canada-West Greenland bowhead whales in relation to season and sea ice, as well as animal sex and age via size. We found no differences with regards to whale sex and size, but we did find evidence that subsurface foraging occurs year-round, with peak foraging occurring in fall (7.3 hrs d⁻¹ ± 5.70 SD; October) and reduced feeding during spring (2.7 hrs d⁻¹ ± 2.55 SD; May). Although sea ice cover is lowest during summer foraging, whales selected areas with 65% (± 36.1 SD) sea ice cover. During winter, bowheads occurred in areas with 90% (± 15.5 SD) ice cover, providing some open water for breathing. The depth of probable foraging varied across seasons with animals conducting epipelagic foraging dives (< 200 m) during spring and summer, and deeper mesopelagic dives (> 400 m) during fall and winter that approached the sea bottom, following the seasonal vertical migration of lipid-rich zooplankton. Our findings suggest that, compared to related species (e.g., right whales), bowheads forage at relatively low rates and over a large geographic area throughout the year. This suggests that bowhead whales have the potential to adjust their behaviours (e.g., increased time allocated to feeding) and shift their distributions (e.g., occupy higher latitude foraging grounds) to adapt to climate-change induced environmental conditions. However, the extent to which energetic consumption may vary seasonally is yet to be determined.
