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1
Lubetkin, S. C., J. E. Zeh, C. Rosa, and J. C. George. "Age estimation for young bowhead whales (Balaena mysticetus) using annual baleen growth increments." Canadian Journal of Zoology 86, no. 6 (2008): 525–38. http://dx.doi.org/10.1139/z08-028.
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We compiled age estimates and baleen plate δ13C data from 86 bowhead whales ( Balaena mysticetus L., 1758). We used previous whale age estimates based on aspartic acid racemization (AAR) and corpora counts to extend the use of δ13C data for age determination from cycle counting to a modified exponential model using annual baleen growth increments. Our approach used the growth increment data from individual whales in a nonlinear mixed effects model to assess both population-level and whale-specific growth parameters. Although age estimates from baleen-based models become less precise as the whales age, and baleen growth and length near steady state, the growth increment model shows promise in estimating ages of bowhead whales 10–13.5 m long with baleen lengths <250 cm, where other techniques are less precise or the data are scarce. Ages estimated using the growth increment data from such whales ranged from 6.4 to 19.8 years.
2
Lubetkin, S. C., J. E. Zeh, and J. C. George. "Statistical modeling of baleen and body length at age in bowhead whales (Balaena mysticetus)." Canadian Journal of Zoology 90, no. 8 (2012): 915–31. http://dx.doi.org/10.1139/z2012-057.
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We used baleen lengths and age estimates from 175 whales and body lengths and age estimates from 205 whales to test which of several single- and multi-stage growth models best characterized age-specific baleen and body lengths for bowhead whales ( Balaena mysticetus L., 1758) with the goal of determining which would be best for predicting whale age based on baleen or body length. Previous age estimates were compiled from several techniques, each of which is valid over a relatively limited set of physical characteristics. The best fitting single-stage growth model was a variation of the von Bertalanffy growth model for both baleen and body length data. Based on Bayesian information criterion, the two- and three-stage versions of the von Bertalanffy model fit the data better than did the single-stage models for both baleen and body length. The best baleen length models can be used to estimate expected ages for bowhead whales with up to 300–325 cm baleen, depending on sex, which correspond to age estimates approaching 60 years. The best body length models can be used to estimate expected ages for male bowhead whales up to 14 m, and female bowheads up to 15.5 m or ages up to approximately 40 years.
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Moore, Sue E. "Is it ‘boom times’ for baleen whales in the Pacific Arctic region?" Biology Letters 12, no. 9 (2016): 20160251. http://dx.doi.org/10.1098/rsbl.2016.0251.
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The marine ecosystem in the Pacific Arctic region has experienced dramatic transformation, most obvious by the loss of sea ice volume (75%), late-summer areal extent (50%) and change in phenology (four to six weeks longer open-water period). This alteration has resulted in an opening of habitat for subarctic species of baleen whales, many of which are recovering in number from severe depletions from commercial whaling in the nineteenth and twentieth centuries. Specifically, humpback, fin and minke whales ( Megaptera novaeangliae , Balaenoptera physalus and Balaenoptera acutorostrata ) are now regularly reported during summer and autumn in the southern Chukchi Sea. These predators of zooplankton and forage fishes join the seasonally resident grey whale ( Eschrichtius robustus ) and the arctic-endemic bowhead whale ( Balaena mysticetus ) in the expanding open-ocean habitat of the Pacific Arctic. Questions arising include: (i) what changes in whale-prey production and delivery mechanisms have accompanied the loss of sea ice, and (ii) how are these five baleen whale species partitioning the expanding ice-free habitat? While there has been no programme of research specifically focused on these questions, an examination of seasonal occurrence, foraging plasticity and (for bowhead whales) body condition suggests that the current state of Pacific Arctic marine ecosystem may be ‘boom times’ for baleen whales. These favourable conditions may be moderated, however, by future shifts in ecosystem structure and/or negative impacts to cetaceans related to increased commercial activities in the region.
4
Volkenandt, Mareike, Ian O’Connor, Jean-Marc Guarini, Simon Berrow, and Ciaran O’Donnell. "Fine-scale spatial association between baleen whales and forage fish in the Celtic Sea." Canadian Journal of Fisheries and Aquatic Sciences 73, no. 2 (2016): 197–204. http://dx.doi.org/10.1139/cjfas-2015-0073.
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Baleen whales can be regularly observed in the Celtic Sea; however, little is known about their local foraging behaviour. The study objective was to determine whether or not baleen whales selectively prey upon particular forage fish species or, on the contrary, is predation on the Celtic Sea plateau driven by random encounters between prey and predator? Concurrent sighting surveys for fin (Balaenoptera physalus), minke (Balaenoptera acutorostrata), and humpback (Megaptera novaeangliae) whales were carried out simultaneously from 2007 to 2013 during dedicated fisheries acoustic surveys assessing the abundance and distribution of forage fish. Probabilities of spatial overlap between baleen whales and forage fish were analysed and compared with the probability of a random encounter. For estimations of foraging threshold and prey selectivity, mean fish biomass and fish length were calculated when baleen whales and forage fish co-occurred. Whales were dominantly observed in areas with herring (Clupea harengus) and sprat (Sprattus sprattus), while areas with mackerel (Scomber scombrus) were not targeted. A prey detection range of up to 8 km was found, which enables baleen whales to track their prey to minimize search effort. Fish densities within the defined foraging distance ranged from 0.001 to 3 kg·m−2 and were correlated to total fish abundance. No prey size selectivity according to fish length was found. By linking baleen whale distribution to high-density herring and sprat areas, it was possible to identify the Celtic Sea as a prey hot spot for baleen whales during autumn.
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Belikov, Stanislav E., and Andrei N. Boltunov. "Distribution and migrations of cetaceans in the Russian Arctic according to observations from aerial ice reconnaissance." NAMMCO Scientific Publications 4 (July 21, 2002): 69. http://dx.doi.org/10.7557/3.2838.
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This paper is based on 748 observations of belugas (Delphinapterus leucas) and 382 observations of baleen whales in the Russian Arctic, the majority of the data provided by aerial reconnaissance of sea ice (ARSI). Although the data are not suitable for the estimation of the number and density of the animals, they represent a multi-year (1958-1995) range of observations to update our knowledge on the seasonal distribution and migrations of the species. Belugas inhabit not only shelf waters but also the zone of the shelf slope and the abyssal zone of the Arctic Ocean, where the animals appear mostly in summer. In winter belugas were observed only in the Barents Sea. In June-August, the frequency of beluga observations was highest in the Laptev Sea, which has previously been believed to have considerably lower numbers of beluga than the Kara and Barents seas. Patterns of seasonal distribution and ice cover suggest the existence of a natural border preventing or reducing population exchange between belugas inhabiting the western and eastern parts of the Russian Arctic. A brief review of available data on distribution of the narwhal (Monodon monoceros) in the Russian Arctic is also given. Two species of baleen whales were frequently seen in the Russian Arctic: the bowhead whale (Balaena mysticetus), and the grey whale (Eschrichtius robustus). The majority of such observations were made in the southeastern part of the East-Siberian Sea and the southern part of the Chukchi Sea. In the Bering Sea baleen whales were usually seen near the Chukotka Peninsula, in Anadyr Bay and southeast of it. Whales were usually seen in ice-free water: observations of whales among rarefied ice and near the ice edge were rare. There were considerable annual and seasonal variations in distribution and migrations of baleen whales in the region, probably caused mainly by the dynamics of ice conditions.
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Werth, Alexander J., Robert W. Harriss, Michael V. Rosario, J. Craig George, and Todd L. Sformo. "Hydration affects the physical and mechanical properties of baleen tissue." Royal Society Open Science 3, no. 10 (2016): 160591. http://dx.doi.org/10.1098/rsos.160591.
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Baleen, an anisotropic oral filtering tissue found only in the mouth of mysticete whales and made solely of alpha-keratin, exhibits markedly differing physical and mechanical properties between dried or (as in life) hydrated states. On average baleen is 32.35% water by weight in North Atlantic right whales ( Eubalaena glacialis ) and 34.37% in bowhead whales ( Balaena mysticetus ). Baleen's wettability measured by water droplet contact angles shows that dried baleen is hydrophobic whereas hydrated baleen is highly hydrophilic. Three-point flexural bending tests of mechanical strength reveal that baleen is strong yet ductile. Dried baleen is brittle and shatters at about 20–30 N mm −2 but hydrated baleen is less stiff; it bends with little force and absorbed water is squeezed out when force is applied. Maximum recorded stress was 4× higher in dried (mean 14.29 N mm −2 ) versus hydrated (mean 3.69 N mm −2 ) baleen, and the flexural stiffness was >10× higher in dried (mean 633N mm −2 ) versus hydrated (mean 58 N mm −2 ) baleen. In addition to documenting hydration's powerful effects on baleen, this study indicates that baleen is far more pliant and malleable than commonly supposed, with implications for studies of baleen's structure and function as well as its susceptibility to oil or other hydrophobic pollutants.
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Werth, Alexander J., Shemar M. Blakeney, and Adrian I. Cothren. "Oil adsorption does not structurally or functionally alter whale baleen." Royal Society Open Science 6, no. 5 (2019): 182194. http://dx.doi.org/10.1098/rsos.182194.
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Mysticete whales filter small prey from seawater using baleen, a unique keratinous oral tissue that grows from the palate, from which it hangs in hundreds of serial plates. Laboratory experiments testing effects of oils on material strength and flexibility, particle capture and tissue architecture of baleen from four mysticete species (bowhead, Balaena mysticetus ; North Atlantic right, Eubalaena glacialis ; fin, Balaenoptera physalus ; humpback, Megaptera novaeangliae ) indicate that baleen is hydrophilic and oleophobic, shedding rather than adsorbing oil. Oils of different weights and viscosities were tested, including six petroleum-based oils and two fish or plankton oils of common whale prey. No notable differences were found by oil type or whale species. Baleen did not adsorb oil; oil was readily rinsed from baleen by flowing water, especially from moving fringes. Microscopic examination shows minimal wrinkling or peeling of baleen's cortical keratin layers, probably due to oil repelling infiltrated water. Combined results cast doubt on fears of baleen fouling by oil; filter porosity is not appreciably affected, but oil ingestion risks remain. Particle capture studies suggest potentially greater danger to mysticetes from plastic pollution than oil.
8
Leaper, Rebecca, and Cara Miller. "Management of Antarctic baleen whales amid past exploitation, current threats and complex marine ecosystems." Antarctic Science 23, no. 6 (2011): 503–29. http://dx.doi.org/10.1017/s0954102011000708.
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AbstractAs baleen whales recover from severe exploitation, they are probably subject to a wide variety of threats within the Antarctic marine ecosystem, including directed take. Here we review both the management and current status of Antarctic baleen whales and consider those threats likely to impact on them. Threats range from global problems - marine pollution and climate change - to localized issues including shipping, habitat disturbance, unregulated wildlife tourism and fishery activities. We identify the most pressing anthropogenic threats to baleen whales including scientific whaling and climate change. It is unclear whether current management approaches will be able to effectively encompass all these threats while also accounting both for the differing levels of scientific understanding and for the differing recovery rates of the whale species. For management we recommend the following: 1) incorporation of both ecosystem considerations and the suite of identified threats not limited to direct take, 2) identification of measurable indicators of changes in whales that allow more certainty in monitoring of populations and the environment, and 3) recognition of significant relationships between baleen whales and habitat features to provide information on distribution and use.
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Stimpert, Alison K., David N. Wiley, Whitlow W. L. Au, Mark P. Johnson, and Roland Arsenault. "‘Megapclicks’: acoustic click trains and buzzes produced during night-time foraging of humpback whales ( Megaptera novaeangliae )." Biology Letters 3, no. 5 (2007): 467–70. http://dx.doi.org/10.1098/rsbl.2007.0281.
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Humpback whales ( Megaptera novaeangliae ) exhibit a variety of foraging behaviours, but neither they nor any baleen whale are known to produce broadband clicks in association with feeding, as do many odontocetes. We recorded underwater behaviour of humpback whales in a northwest Atlantic feeding area using suction-cup attached, multi-sensor, acoustic tags (DTAGs). Here we describe the first recordings of click production associated with underwater lunges from baleen whales. Recordings of over 34 000 ‘megapclicks’ from two whales indicated relatively low received levels at the tag (between 143 and 154 dB re 1 μPa pp), most energy below 2 kHz, and interclick intervals often decreasing towards the end of click trains to form a buzz. All clicks were recorded during night-time hours. Sharp body rolls also occurred at the end of click bouts containing buzzes, suggesting feeding events. This acoustic behaviour seems to form part of a night-time feeding tactic for humpbacks and also expands the known acoustic repertoire of baleen whales in general.
10
Werth, Alexander J. "Hydrodynamic and Sensory Factors Governing Response of Copepods to Simulated Predation by Balaenid Whales." International Journal of Ecology 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/208913.
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Predator/prey interactions between copepods and balaenid (bowhead and right) whales were studied with controlled lab experiments using moving baleen in still water and motionless baleen in flowing water to simulate zooplankton passage toward, into, and through the balaenid oral cavity. Copepods showed a lesser escape response to baleen and to a model head simulating balaenid oral hydrodynamics than to other objects. Copepod escape response increased as water flow and body size increased and was greatest at distances ≥10 cm from baleen and at copepod density = 10,000 m−3. Data from light/dark experiments suggest that escape is based on mechanoreception, not vision. The model head captured 88% of copepods. Results support previous research showing hydrodynamic effects within a whale’s oral cavity create slight suction pressures to draw in prey or at least preclude formation of an anterior compressive bow wave that could scatter or alert prey to the presence of the approaching whale.
11
Häussermann, Verena, Carolina S. Gutstein, Michael Beddington, et al. "Largest baleen whale mass mortality during strong El Niño event is likely related to harmful toxic algal bloom." PeerJ 5 (May 31, 2017): e3123. http://dx.doi.org/10.7717/peerj.3123.
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While large mass mortality events (MMEs) are well known for toothed whales, they have been rare in baleen whales due to their less gregarious behavior. Although in most cases the cause of mortality has not been conclusively identified, some baleen whale mortality events have been linked to bio-oceanographic conditions, such as harmful algal blooms (HABs). In Southern Chile, HABs can be triggered by the ocean–atmosphere phenomenon El Niño. The frequency of the strongest El Niño events is increasing due to climate change. In March 2015, by far the largest reported mass mortality of baleen whales took place in a gulf in Southern Chile. Here, we show that the synchronous death of at least 343, primarily sei whales can be attributed to HABs during a building El Niño. Although considered an oceanic species, the sei whales died while feeding near to shore in previously unknown large aggregations. This provides evidence of new feeding grounds for the species. The combination of older and newer remains of whales in the same area indicate that MMEs have occurred more than once in recent years. Large HABs and reports of marine mammal MMEs along the Northeast Pacific coast may indicate similar processes in both hemispheres. Increasing MMEs through HABs may become a serious concern in the conservation of endangered whale species.
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Stafford, K. M., C. Lydersen, Ø. Wiig, and K. M. Kovacs. "Extreme diversity in the songs of Spitsbergen's bowhead whales." Biology Letters 14, no. 4 (2018): 20180056. http://dx.doi.org/10.1098/rsbl.2018.0056.
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Almost all mammals communicate using sound, but few species produce complex songs. Two baleen whales sing complex songs that change annually, though only the humpback whale ( Megaptera novaeangliae ) has received much research attention. This study focuses on the other baleen whale singer, the bowhead whale ( Balaena mysticetus ). Members of the Spitsbergen bowhead whale population produced 184 different song types over a 3-year period, based on duty-cycled recordings from a site in Fram Strait in the northeast Atlantic. Distinct song types were recorded over short periods, lasting at most some months. This song diversity could be the result of population expansion, or immigration of animals from other populations that are no longer isolated from each other by heavy sea ice. However, this explanation does not account for the within season and annual shifting of song types. Other possible explanations for the extraordinary diversity in songs could be that it results either from weak selection pressure for interspecific identification or for maintenance of song characteristics or, alternatively, from strong pressure for novelty in a small population.
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Stimmelmayr, R., DS Rotstein, G. Sheffield, and JC George. "Subcutaneous, abdominal, and thoracic encapsulated fat necrosis in bowhead whales Balaena mysticetus from Alaska, USA." Diseases of Aquatic Organisms 145 (July 15, 2021): 159–64. http://dx.doi.org/10.3354/dao03605.
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We describe a case series of encapsulated fat necrosis with subcutaneous, abdominal, and thoracic locations in 7 subsistence-harvested bowhead whales Balaena mysticetus. Masses had a variably-dense fibrous capsule surrounding necrotic adipocytes and calcium salts (saponification). One animal also had prior concussive injury, pleural fibrosis, and hepatic lipoma; the other animals had no significant findings. The described condition is uncommon in bowhead whales, with 7/575 (1.2%) observed from 1996 to 2015. The exact mechanisms of development of encapsulated fat necrosis in bowhead whales remain to be determined. Encapsulated fat necrosis has been reported in other baleen whales, humans, and cows. It is usually an incidental finding during post-mortem examination that needs to be differentiated from neoplastic and inflammatory lesions, as the latter may have public health implications. Assessment of further cases in bowhead whales and other baleen whales is warranted to better understand their pathogenesis.
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Rolland, Rosalind M., Susan E. Parks, Kathleen E. Hunt, et al. "Evidence that ship noise increases stress in right whales." Proceedings of the Royal Society B: Biological Sciences 279, no. 1737 (2012): 2363–68. http://dx.doi.org/10.1098/rspb.2011.2429.
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Baleen whales ( Mysticeti ) communicate using low-frequency acoustic signals. These long-wavelength sounds can be detected over hundreds of kilometres, potentially allowing contact over large distances. Low-frequency noise from large ships (20–200 Hz) overlaps acoustic signals used by baleen whales, and increased levels of underwater noise have been documented in areas with high shipping traffic. Reported responses of whales to increased noise include: habitat displacement, behavioural changes and alterations in the intensity, frequency and intervals of calls. However, it has been unclear whether exposure to noise results in physiological responses that may lead to significant consequences for individuals or populations. Here, we show that reduced ship traffic in the Bay of Fundy, Canada, following the events of 11 September 2001, resulted in a 6 dB decrease in underwater noise with a significant reduction below 150 Hz. This noise reduction was associated with decreased baseline levels of stress-related faecal hormone metabolites (glucocorticoids) in North Atlantic right whales ( Eubalaena glacialis ). This is the first evidence that exposure to low-frequency ship noise may be associated with chronic stress in whales, and has implications for all baleen whales in heavy ship traffic areas, and for recovery of this endangered right whale population.
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Hobson, Keith A., and Don M. Schell. "Stable carbon and nitrogen isotope patterns in baleen from eastern Arctic bowhead whales (Balaena mysticetus)." Canadian Journal of Fisheries and Aquatic Sciences 55, no. 12 (1998): 2601–7. http://dx.doi.org/10.1139/f98-142.
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Previous measurements of naturally occurring stable isotopes of carbon (delta13C) and nitrogen (delta15N) along the baleen plates of western Arctic bowhead whales (Balaena mysticetus) have provided a continuous lifetime record of the feeding or nutritional ecology of these animals that migrate annually between isotopically different foodwebs. However, virtually nothing was known about isotopic patterns of eastern Arctic bowheads. We measured delta13C and delta15N values along the baleen plates of three eastern and one western Arctic bowhead whales taken from Canadian waters in 1988 and 1996. In contrast to western Arctic animals, we found strong evidence for periodic fluctuations in delta15N but not delta13C values in the eastern Arctic specimens. We interpret these results as evidence that eastern Arctic animals do not move between foodwebs that differ in delta13C signature and suggest that these whales either (i) move annually between areas isotopically enriched in 15N but not 13C, (ii) shift diet annually by about one third of a trophic level, or (iii) undergo seasonal fasting that results in enrichment of baleen delta15N resulting from protein catabolism.
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Schall, Elena, Karolin Thomisch, Olaf Boebel, Gabriele Gerlach, Stefanie Spiesecke, and Ilse Van Opzeeland. "Large-scale spatial variabilities in the humpback whale acoustic presence in the Atlantic sector of the Southern Ocean." Royal Society Open Science 7, no. 12 (2020): 201347. http://dx.doi.org/10.1098/rsos.201347.
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Southern Hemisphere humpback whales ( Megaptera novaeangliae ) inhabit a wide variety of ecosystems including both low- and high-latitude areas. Understanding the habitat selection of humpback whale populations is key for humpback whale stock management and general ecosystem management. In the Atlantic sector of the Southern Ocean ( ASSO ), the investigation of baleen whale distribution by sighting surveys is temporally restricted to the austral summer. The implementation of autonomous passive acoustic monitoring, in turn, allows the study of vocal baleen whales year-round. This study describes the results of analysing passive acoustic data spanning 12 recording positions throughout the ASSO applying a combination of automatic and manual analysis methods to register humpback whale acoustic activity. Humpback whales were present at nine recording positions with higher acoustic activities towards lower latitudes and the eastern and western edges of the ASSO . During all months, except December (the month with the fewest recordings), humpback whale acoustic activity was registered in the ASSO . The acoustic presence of humpback whales at various locations in the ASSO confirms previous observations that part of the population remains in high-latitude waters beyond austral summer, presumably to feed. The spatial and temporal extent of humpback whale presence in the ASSO suggests that this area may be used by multiple humpback whale breeding populations as a feeding ground.
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Piatt, John F., David A. Methven, Alan E. Burger, Ruth L. McLagan, Vicki Mercer, and Elizabeth Creelman. "Baleen whales and their prey in a coastal environment." Canadian Journal of Zoology 67, no. 6 (1989): 1523–30. http://dx.doi.org/10.1139/z89-217.
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Patterns of abundance of humpback (Megaptera novaeangliae), fin (Balaenoptera physalus), and minke (Balaenoptera acutorostrata) whales are described in relation to the abundance of their primary prey, capelin (Mallotus villosus), during 1982–1985 at Witless Bay, Newfoundland. The abundance ratio of the three whale species was 10:1:3.5, respectively. Abundance of all whale species was strongly correlated with abundance of capelin through each season and between years. Capelin abundance accounted for 63% of the variation in whale numbers in 1983 and 1984, while environmental parameters (e.g., water temperatures) accounted for little variance. The amount of capelin consumed by whales was small (< 2%) compared with the amount available. All three species overlapped temporally at Witless Bay, but spatial overlap was reduced as fins occurred primarily offshore, minkes primarily inshore, and humpbacks in bay habitats of intermediate depth.
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Di Iorio, Lucia, and Christopher W. Clark. "Exposure to seismic survey alters blue whale acoustic communication." Biology Letters 6, no. 1 (2009): 51–54. http://dx.doi.org/10.1098/rsbl.2009.0651.
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The ability to perceive biologically important sounds is critical to marine mammals, and acoustic disturbance through human-generated noise can interfere with their natural functions. Sounds from seismic surveys are intense and have peak frequency bands overlapping those used by baleen whales, but evidence of interference with baleen whale acoustic communication is sparse. Here we investigated whether blue whales ( Balaenoptera musculus ) changed their vocal behaviour during a seismic survey that deployed a low-medium power technology (sparker). We found that blue whales called consistently more on seismic exploration days than on non-exploration days as well as during periods within a seismic survey day when the sparker was operating. This increase was observed for the discrete, audible calls that are emitted during social encounters and feeding. This response presumably represents a compensatory behaviour to the elevated ambient noise from seismic survey operations.
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McAlpine, Donald F. "Size and growth of heart, liver, and kidneys in North Atlantic fin (Balaenoptera physalus), sei (B. borealis), and sperm (Physeter macrocephalus) whales." Canadian Journal of Zoology 63, no. 6 (1985): 1402–9. http://dx.doi.org/10.1139/z85-210.
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Size and growth of heart, liver, and kidneys in fin (Balaenoptera physalus), sei (B. borealis), and sperm (Physeter macrocephalus) whales taken commercially off Iceland during the 1980 season are compared and examined relative to organ weights for terrestrial mammals. In agreement with the work of previous investigators, the sperm whale is shown to have a relatively smaller heart. However, contrary to previous analysis, fin and sei whales are shown to have relative heart sizes not radically different from those of terrestrial mammals. It is suggested that the differences in relative heart size between the baleen and toothed whales are a reflection of the greater swimming speeds that the baleen whales are capable of attaining. This analysis confirms that marine cetaceans have relatively much larger livers than terrestrial mammals and that they also appear to have relatively larger kidneys. The results presented here, however, show fin, sei, and sperm whales to have relative kidney sizes less than half as great as those given in previous analyses. Growth gradients in the three organs show a distinct pattern of divergence between sperm (Odontocete) and fin and sei (Mysticete) whales.
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Parks, Susan E., Dana A. Cusano, Sofie M. Van Parijs, and Douglas P. Nowacek. "Acoustic crypsis in communication by North Atlantic right whale mother–calf pairs on the calving grounds." Biology Letters 15, no. 10 (2019): 20190485. http://dx.doi.org/10.1098/rsbl.2019.0485.
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Mammals with dependent young often rely on cryptic behaviour to avoid detection by potential predators. In the mysticetes, large baleen whales, young calves are known to be vulnerable to direct predation from both shark and orca predators; therefore, it is possible that mother–calf pairs may show cryptic behaviours to avoid the attention of predators. Baleen whales primarily communicate through low-frequency acoustic signals, which can travel over long ranges. In this study, we explore the potential for acoustic crypsis, a form of cryptic behaviour to avoid predator detection, in North Atlantic right whale mother–calf pairs. We predicted that mother–calf pairs would either show reduced calling rates, reduced call amplitude or a combination of these behavioural modifications when compared with other demographic groups in the same habitat. Our results show that right whale mother–calf pairs have a strong shift in repertoire usage, significantly reducing the number of higher amplitude, long-distance communication signals they produced when compared with juvenile and pregnant whales in the same habitat. These observations show that right whale mother–calf pairs rely upon acoustic crypsis, potentially to minimize the risk of acoustic eavesdropping by predators.
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Liu, Mingming, Wenzhi Lin, Mingli Lin, et al. "The First Attempt of Satellite Tracking on Occurrence and Migration of Bryde’s Whale (Balaenoptera edeni) in the Beibu Gulf." Journal of Marine Science and Engineering 9, no. 8 (2021): 796. http://dx.doi.org/10.3390/jmse9080796.
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Satellite-tagging is increasingly becoming a powerful biotelemetry approach to obtain remote measurement through tracking free-living cetaceans, which can fill knowledge gaps on cetaceans and facilitate conservation management. Here, we made a first biologging attempt on baleen whales in Chinese waters. An adult Bryde’s whale in the Beibu Gulf was tagged to investigate potential occurrence areas and migration routes of this poorly studied species. The whale was satellite-tracked for ~6 days with 71 filtered Argos satellite locations, resulting in a linear movement distance of 464 km. At each satellite-tracking location, the water depth was measured as 42.1 ± 24.8 m on average. During the satellite-tracking period, the whale’s moving speed was estimated at 5.33 ± 4.01 km/h. These findings expanded the known distribution areas of Bryde’s whales in the Beibu Gulf and provided an important scientific basis for the regional protection of this species. We suggest that fine-scale movements, habitat use, and migratory behavior of Bryde’s whales in the Beibu Gulf need more biotelemetry research, using long-term satellite-tracking tags and involving enough individuals. Furthermore, the genetic relationship and possible connectivity of Bryde’s whales in the Beibu Gulf and adjacent waters should be examined.
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Goldbogen, Jeremy A., Brandon L. Southall, Stacy L. DeRuiter, et al. "Blue whales respond to simulated mid-frequency military sonar." Proceedings of the Royal Society B: Biological Sciences 280, no. 1765 (2013): 20130657. http://dx.doi.org/10.1098/rspb.2013.0657.
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Mid-frequency military (1–10 kHz) sonars have been associated with lethal mass strandings of deep-diving toothed whales, but the effects on endangered baleen whale species are virtually unknown. Here, we used controlled exposure experiments with simulated military sonar and other mid-frequency sounds to measure behavioural responses of tagged blue whales ( Balaenoptera musculus ) in feeding areas within the Southern California Bight. Despite using source levels orders of magnitude below some operational military systems, our results demonstrate that mid-frequency sound can significantly affect blue whale behaviour, especially during deep feeding modes. When a response occurred, behavioural changes varied widely from cessation of deep feeding to increased swimming speed and directed travel away from the sound source. The variability of these behavioural responses was largely influenced by a complex interaction of behavioural state, the type of mid-frequency sound and received sound level. Sonar-induced disruption of feeding and displacement from high-quality prey patches could have significant and previously undocumented impacts on baleen whale foraging ecology, individual fitness and population health.
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Wray, Janie, Eric Keen, and Éadin N. O’Mahony. "Social survival: Humpback whales (Megaptera novaeangliae) use social structure to partition ecological niches within proposed critical habitat." PLOS ONE 16, no. 6 (2021): e0245409. http://dx.doi.org/10.1371/journal.pone.0245409.
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Animal culture and social bonds are relevant to wildlife conservation because they influence patterns of geography, behavior, and strategies of survival. Numerous examples of socially-driven habitat partitioning and ecological-niche specialization can be found among vertebrates, including toothed whales. But such social-ecological dynamics, described here as ‘social niche partitioning’, are not known among baleen whales, whose societies—particularly on foraging grounds—are largely perceived as unstructured and incidental to matters of habitat use and conservation. However, through 16 years of behavioral observations and photo-identifications of humpback whales (Megaptera novaeangliae) feeding within a fjord system in the Canadian Pacific (primarily within Gitga’at First Nation waters), we have documented long-term pair bonds (up to 12 years) as well as a complex societal structure, which corresponds closely to persistent patterns in feeding strategy, long-term site fidelity (extended occupancy and annual rate of return up to 75%), specific geographic preferences within the fjord system, and other forms of habitat use. Randomization tests of network congruency and clustering algorithms were used to test for overlap in patterns of social structure and habitat use, which confirmed the occurrence of social niche partitioning on the feeding grounds of this baleen whale species. In addition, we document the extensive practice of group bubble net feeding in Pacific Canada. This coordinated feeding behavior was found to strongly mediate the social structure and habitat use within this humpback whale society. Additionally, during our 2004–2019 study, we observed a shift in social network structure in 2010–2012, which corresponded with environmental and demographic shifts including a sudden decline in the population’s calving rate. Our findings indicate that the social lives of humpback whales, and perhaps baleen whales generally, are more complex than previously supposed and should be a primary consideration in the assessment of potential impacts to important habitat.
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Owen, Kylie, K. Curt S. Jenner, Micheline-Nicole M. Jenner, Robert D. McCauley, and Russel D. Andrews. "Water temperature correlates with baleen whale foraging behaviour at multiple scales in the Antarctic." Marine and Freshwater Research 70, no. 1 (2019): 19. http://dx.doi.org/10.1071/mf17288.
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How baleen whales locate prey and how environmental change may influence whale foraging success are not well understood. Baleen whale foraging habitat has largely been described at a population level, yet population responses to change are the result of individual strategies across multiple scales. This study aimed to determine how the foraging behaviour of individual whales varied relative to environmental conditions along their movement path. Biotelemetry devices provided information on humpback whale (Megaptera novaeangliae) movement at two spatial scales in East Antarctica, and a mixed modelling approach was used at a medium scale (tens of kilometres) to determine which environmental factors correlated with a change in foraging behaviour. Water temperature was linked to a change in foraging behaviour at both spatial scales. At the medium scale, warmer water was associated with the resident state, commonly assumed to represent periods of foraging behaviour. However, fine-scale analyses suggested that cooler water was associated with a higher feeding rate. Variation in whale foraging behaviour with changes in water temperature adds support to the hypothesis that whales may be able to track environmental conditions to find prey. Future research should investigate this pattern further, given the predicted rise in water temperatures under climate-change scenarios.
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Fordyce, R. Ewan, and Felix G. Marx. "The pygmy right whale Caperea marginata : the last of the cetotheres." Proceedings of the Royal Society B: Biological Sciences 280, no. 1753 (2013): 20122645. http://dx.doi.org/10.1098/rspb.2012.2645.
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The pygmy right whale, Caperea marginata , is the most enigmatic of the living baleen whales (Mysticeti). Its highly disparate morphology and the virtual absence of a described fossil record have made it extremely difficult to place Caperea into a broader evolutionary context, and molecular and morphological studies have frequently contradicted each other as to the origins and phylogenetic relationships of the species. Our study of a wealth of material from New Zealand collections, representing a wide range of ontogenetic stages, has identified several new features previously unreported in Caperea , which suggest that the pygmy right whale may be the last survivor of the supposedly extinct family Cetotheriidae. This hypothesis is corroborated by both morphology-based and total evidence cladistic analyses, including 166 morphological characters and 23 taxa, representing all the living and extinct families of toothless baleen whales. Our results allow us to formally refer Caperea to Cetotheriidae, thus resurrecting the latter from extinction and helping to clarify the origins of a long-problematic living species.
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Friedlaender, Ari S., David W. Johnston, Reny B. Tyson, et al. "Multiple-stage decisions in a marine central-place forager." Royal Society Open Science 3, no. 5 (2016): 160043. http://dx.doi.org/10.1098/rsos.160043.
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Air-breathing marine animals face a complex set of physical challenges associated with diving that affect the decisions of how to optimize feeding. Baleen whales (Mysticeti) have evolved bulk-filter feeding mechanisms to efficiently feed on dense prey patches. Baleen whales are central place foragers where oxygen at the surface represents the central place and depth acts as the distance to prey. Although hypothesized that baleen whales will target the densest prey patches anywhere in the water column, how depth and density interact to influence foraging behaviour is poorly understood. We used multi-sensor archival tags and active acoustics to quantify Antarctic humpback whale foraging behaviour relative to prey. Our analyses reveal multi-stage foraging decisions driven by both krill depth and density. During daylight hours when whales did not feed, krill were found in deep high-density patches. As krill migrated vertically into larger and less dense patches near the surface, whales began to forage. During foraging bouts, we found that feeding rates (number of feeding lunges per hour) were greatest when prey was shallowest, and feeding rates decreased with increasing dive depth. This strategy is consistent with previous models of how air-breathing diving animals optimize foraging efficiency. Thus, humpback whales forage mainly when prey is more broadly distributed and shallower, presumably to minimize diving and searching costs and to increase feeding rates overall and thus foraging efficiency. Using direct measurements of feeding behaviour from animal-borne tags and prey availability from echosounders, our study demonstrates a multi-stage foraging process in a central place forager that we suggest acts to optimize overall efficiency by maximizing net energy gain over time. These data reveal a previously unrecognized level of complexity in predator–prey interactions and underscores the need to simultaneously measure prey distribution in marine central place forager studies.
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Ukishima, Yoshiyuki, Masahiko Kino, Hiroyuki Kubota, Shiro Wada, and Shoji Okada. "Identification of Whale Species by Thin-Layer Isoelectric Focusing of Sarcoplasmic Proteins1." Journal of AOAC INTERNATIONAL 74, no. 6 (1991): 943–50. http://dx.doi.org/10.1093/jaoac/74.6.943.
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Abstract Thin-layer isoelectric focusing was applied to the identification of whale (Cetacea) species by using water-soluble sarcoplasmic proteins of skeletal muscles. Twenty-eight samples consisting of 4 species (10 samples) of baleen whales (Mysticeti) and 8 species (18 samples) of toothed whales (Odontoceti) were analyzed. Each sample (approximately 1 g) was electrophoresed with Ampholine PAGplate, pH 3.5-9.5. The electrophoretic profiles were species-specific on the 4 toothed whale species that did not have a marked intra-species difference, and all 4 baleen whale species. However, the profiles were not specific on the 4 other dolphin species, even though they were discriminable from the other 4 toothed whale species. Numerical values of pls and relative peak heights were obtained by densitometric analysis of the isoelectro-focused protein bands. The bands were also species-specific for the 8 toothed whale species mentioned. The values may be applicable to species identification without the need for a standard sample, which may not be readily obtainable. Experiments on test samples of minke and sei whales showed that bloodletting with ice water made the densities of isoelectro-focused bands thinner, although species identification was still possible by using the Inside part of muscles. Heat treatment at below 60°C for 10 min caused little denaturation; at higher temperatures the protein bands were diminished in a temperature-dependent fashion. Therefore, the present isoelectric focusing analysis should be applicable to small samples of whale meat, excluding several species of dolphins.
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Würsig, Bernd. "The Behavior of Baleen Whales." Scientific American 258, no. 4 (1988): 102–7. http://dx.doi.org/10.1038/scientificamerican0488-102.
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Clapham, Phil. "Why do Baleen Whales Migrate?." Marine Mammal Science 17, no. 2 (2001): 432–36. http://dx.doi.org/10.1111/j.1748-7692.2001.tb01289.x.
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Cassoff, RM, KM Moore, WA McLellan, SG Barco, DS Rotstein, and MJ Moore. "Lethal entanglement in baleen whales." Diseases of Aquatic Organisms 96, no. 3 (2011): 175–85. http://dx.doi.org/10.3354/dao02385.
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Popov, Ya. "Toothless Ancestor of Baleen Whales." Priroda, no. 12 (December 2018): 48–49. http://dx.doi.org/10.31857/s0032874x0003331-3.
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Shipps, B. K., Carlos Mauricio Peredo, and Nicholas D. Pyenson. "Borealodon osedax , a new stem mysticete (Mammalia, Cetacea) from the Oligocene of Washington State and its implications for fossil whale-fall communities." Royal Society Open Science 6, no. 7 (2019): 182168. http://dx.doi.org/10.1098/rsos.182168.
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Baleen whales (mysticetes) lack teeth as adults and instead filter feed using keratinous baleen plates. They do not echolocate with ultrasonic frequencies like toothed whales but are instead known for infrasonic acoustics. Both baleen and infrasonic hearing are separately considered key innovations linked to their gigantism, evolutionary success and ecological diversity. The earliest mysticetes had teeth, and the phylogenetic position of many so-called toothed mysticetes remains debated, including those belonging to the nominal taxonomic groups Llanocetidae, Mammalodontidae and Aetiocetidae. Here, we report a new stem mysticete, Borealodon osedax gen. et sp. nov., from the Oligocene of Washington State, USA. Borealodon preserves multi-cusped teeth with apical wear; microCT scans of the inner ear indicate that the minimum frequency hearing limit of Borealodon was similar to mammalodontids. Borealodon is not recovered within a monophyletic Mammalodontidae nor a monophyletic Aetiocetidae; instead, it represents an unnamed lineage of stem Mysticeti, adding to the diversity of stem mysticetes, especially across the Rupelian–Chattian boundary. Furthermore, the presence of a putative chemosynthetic bivalve along with Osedax , a bone-boring annelid, found in association with the type specimen of Borealodon , offer more insights into the evolution of deep-sea whale-fall communities.
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Uchida, Mayuka, Ippei Suzuki, Keizo Ito, et al. "Estimation of the feeding record of pregnant Antarctic minke whales (Balaenoptera bonaerensis) using carbon and nitrogen stable isotope analysis of baleen plates." Polar Biology 44, no. 3 (2021): 621–29. http://dx.doi.org/10.1007/s00300-021-02816-5.
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AbstractAntarctic minke whales (Balaenoptera bonaerensis) are migratory capital breeders that experience intensive summer feeding on Antarctic krill (Euphausia superba) in the Southern Ocean and winter breeding at lower latitudes, but their prey outside of the Antarctic is unknown. Stable isotope analyses were conducted on δ13C and δ15N from the baleen plates of ten pregnant Antarctic minke whales to understand the growth rate of the baleen plate and their diet in lower latitudes. Two to three oscillations along the length of the edge of the baleen plate were observed in δ15N, and the annual growth rate was estimated to be 75.2 ± 20.4 mm, with a small amplitude (0.97 ± 0.21 ‰). Bayesian stable isotope mixing models were used to understand the dominant prey that contributed to the isotopic component of the baleen plate using Antarctic krill from the stomach contents and reported values of Antarctic coastal krill (Euphausia crystallorophias), Antarctic silver fish (Pleuragramma antarcticum), Australian krill spp., and Australian pelagic fish spp.. The models showed that the diet composition of the most recent three records from the base of the baleen plates (model 1) and the highest δ15N values in each baleen plate (model 2) were predominantly Antarctic krill, with a contribution rate of approximately 80%. The rates were approximately 10% for Antarctic coastal krill and less than 2.0% for the two Australian prey groups in both models. These results suggest that pregnant Antarctic minke whales did not feed on enough prey outside of the Antarctic to change the stable isotope values in their baleen plates.
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Peredo, Carlos Mauricio, and Nicholas D. Pyenson. "Morphological variation of the relictual alveolar structures in the mandibles of baleen whales." PeerJ 9 (July 30, 2021): e11890. http://dx.doi.org/10.7717/peerj.11890.
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Living baleen whales (mysticetes) are bulk filter feeders that use keratinous baleen plates to filter food from prey laden water. Extant mysticetes are born entirely edentulous, though they possess tooth buds early in ontogeny, a trait inherited from toothed ancestors. The mandibles of extant baleen whales have neither teeth nor baleen; teeth are resorbed in utero and baleen grows only on the palate. The mandibles of extant baleen whales also preserve a series of foramina and associated sulci that collectively form an elongated trough, called the alveolar groove. Despite this name, it remains unclear if the alveolar groove of edentulous mysticetes and the dental structures of toothed mammals are homologous. Here, we describe and quantify the anatomical diversity of these structures across extant mysticetes and compare their variable morphologies across living taxonomic groups (i.e., Balaenidae, Neobalaenidae, Eschrichtiidae, and Balaenopteridae). Although we found broad variability across taxonomic groups for the alveolar groove length, occupying approximately 60–80 percent of the mandible’s total curvilinear length (CLL) across all taxa, the relictual alveolar foramen showed distinct patterns, ranging between 15–25% CLL in balaenids, while ranging between 3–12% CLL in balaenopterids. This variability and the morphological patterning along the body of the mandible is consistent with the hypothesis that the foramina underlying the alveolar groove reflect relictual alveoli. These findings also lay the groundwork for future histological studies to examine the contents of these foramina and clarify their potential role in the feeding process.
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Park, Travis, Alistair R. Evans, Stephen J. Gallagher, and Erich M. G. Fitzgerald. "Low-frequency hearing preceded the evolution of giant body size and filter feeding in baleen whales." Proceedings of the Royal Society B: Biological Sciences 284, no. 1848 (2017): 20162528. http://dx.doi.org/10.1098/rspb.2016.2528.
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Living baleen whales (mysticetes) produce and hear the lowest-frequency (infrasonic) sounds among mammals. There is currently debate over whether the ancestor of crown cetaceans (Neoceti) was able to detect low frequencies. However, the lack of information on the most archaic fossil mysticetes has prevented us from determining the earliest evolution of their extreme acoustic biology. Here, we report the first anatomical analyses and frequency range estimation of the inner ear in Oligocene (34–23 Ma) fossils of archaic toothed mysticetes from Australia and the USA. The cochlear anatomy of these small fossil mysticetes resembles basilosaurid archaeocetes, but is also similar to that of today's baleen whales, indicating that even the earliest mysticetes detected low-frequency sounds, and lacked ultrasonic hearing and echolocation. This suggests that, in contrast to recent research, the plesiomorphic hearing condition for Neoceti was low frequency, which was retained by toothed mysticetes, and the high-frequency hearing of odontocetes is derived. Therefore, the low-frequency hearing of baleen whales has remained relatively unchanged over the last approximately 34 Myr, being present before the evolution of other signature mysticete traits, including filter feeding, baleen and giant body size.
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Hoekstra, P. F., L. A. Dehn, J. C. George, K. R. Solomon, D. CG Muir, and T. M. O'Hara. "Trophic ecology of bowhead whales (Balaena mysticetus) compared with that of other arctic marine biota as interpreted from carbon-, nitrogen-, and sulfur-isotope signatures." Canadian Journal of Zoology 80, no. 2 (2002): 223–31. http://dx.doi.org/10.1139/z01-229.
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In this study, stable carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) isotope ratios were measured in muscle tissue from the BeringChukchiBeaufort Sea population of bowhead whales (Balaena mysticetus; n = 84) and various marine biota between 1997 and 2000. In previous investigations, stable carbon and nitrogen isotope ratios in baleen from this population have been used to elucidate age, migratory behaviour, and feeding ecology. However, information on δ13C, δ15N, and δ34S isotope patterns in bowhead whale muscle tissue and variability within the Bering Sea population is limited. Stable sulfur isotope values did not vary with δ13C enrichment for three consecutive seasons (n = 53) and this suggests that habitat selection by bowhead whales was consistent over the sampling period. We found that in contrast to other studies, seasonal differences (spring versus fall) in δ13C values were not associated with seasonal changes in δ15N values, suggesting either that bowhead whales maintain a consistently lower trophic position relative to other marine mammals or that stable carbon and nitrogen isotope fractionation is tissue-dependent and (or) isotope-dependent within this species. Seasonal fluctuation in δ13C values was consistent for all age classes of bowhead whales and suggests that the Bering and Beaufort seas are both important regions for feeding.
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Fitzgerald, Erich M. G. "A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales." Proceedings of the Royal Society B: Biological Sciences 273, no. 1604 (2006): 2955–63. http://dx.doi.org/10.1098/rspb.2006.3664.
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Extant baleen whales (Cetacea, Mysticeti) are all large filter-feeding marine mammals that lack teeth as adults, instead possessing baleen, and feed on small marine animals in bulk. The early evolution of these superlative mammals, and their unique feeding method, has hitherto remained enigmatic. Here, I report a new toothed mysticete from the Late Oligocene of Australia that is more archaic than any previously described. Unlike all other mysticetes, this new whale was small, had enormous eyes and lacked derived adaptations for bulk filter-feeding. Several morphological features suggest that this mysticete was a macrophagous predator, being convergent on some Mesozoic marine reptiles and the extant leopard seal ( Hydrurga leptonyx ). It thus refutes the notions that all stem mysticetes were filter-feeders, and that the origins and initial radiation of mysticetes was linked to the evolution of filter-feeding. Mysticetes evidently radiated into a variety of disparate forms and feeding ecologies before the evolution of baleen or filter-feeding. The phylogenetic context of the new whale indicates that basal mysticetes were macrophagous predators that did not employ filter-feeding or echolocation, and that the evolution of characters associated with bulk filter-feeding was gradual.
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Edds, Peggy L., and J. Andrew F. Macfarlane. "Occurrence and general behavior of balaenopterid cetaceans summering in the St. Lawrence Estuary, Canada." Canadian Journal of Zoology 65, no. 6 (1987): 1363–76. http://dx.doi.org/10.1139/z87-216.
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Baleen whale movements were monitored from a hillside on the north shore of the St. Lawrence Estuary from 28 June to 27 September 1979. No diurnal or tidal relationships were apparent for the two most abundant species, the minke and finback. Single minke whales were seen almost daily. Adult pairs were only seen on four dates, and no adult-calf pairs were observed. Twenty-two small minkes were observed; three were possibly 1st-year calves. Finbacks occurred singly and in groups, particularly later in the field season. Resightings of distinctive finbacks indicate that adult pairings are temporary. One finback had been seen in the area in 1973–1975. Adult–calf pairs and seven single juveniles were also seen. Observations of finbacks pursued by whale watchers provide evidence that some regulation of the rapidly growing whale-watching industry may be warranted. Blue whales and humpback whales were seen far less frequently than minkes and finbacks. The relative abundances of minke, finback, and humpback were similar to 1973–1974 in the same area: however, blue whales were seen far more frequently in the past.
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Fournet, Michelle E. H., Lauren Jacobsen, Christine M. Gabriele, David K. Mellinger, and Holger Klinck. "More of the same: allopatric humpback whale populations share acoustic repertoire." PeerJ 6 (July 30, 2018): e5365. http://dx.doi.org/10.7717/peerj.5365.
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Background Humpback whales (Megaptera novaeangliae) are a widespread, vocal baleen whale best known for producing song, a complex, repetitive, geographically distinct acoustic signal sung by males, predominantly in a breeding context. Humpback whales worldwide also produce non-song vocalizations (“calls”) throughout their migratory range, some of which are stable across generations. Methods We looked for evidence that temporally stable call types are shared by two allopatric humpback whale populations while on their northern hemisphere foraging grounds in order to test the hypothesis that some calls, in strong contrast to song, are innate within the humpback whale acoustic repertoire. Results Despite being geographically and genetically distinct populations, humpback whales in Southeast Alaska (North Pacific Ocean) share at least five call types with conspecifics in Massachusetts Bay (North Atlantic Ocean). Discussion This study is the first to identify call types shared by allopatric populations, and provides evidence that some call types may be innate.
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Brüniche-Olsen, Anna, John W. Bickham, Celine A. Godard-Codding, et al. "Influence of Holocene habitat availability on Pacific gray whale (Eschrichtius robustus) population dynamics as inferred from whole mitochondrial genome sequences and environmental niche modeling." Journal of Mammalogy 102, no. 4 (2021): 986–99. http://dx.doi.org/10.1093/jmammal/gyab032.
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Abstract Environmental changes since the Pleistocene and commercial whaling in the last few centuries have drastically reduced many whale populations, including gray whales in the North Pacific. Herein we use complete mitogenome sequences from 74 individuals to evaluate gray whale phylogeography and historical demography, then use environmental niche modeling to assess how habitat availability has changed through time for Pacific gray whales. We identify a large degree of haplotype sharing between gray whales sampled in Russian and Mexican waters, coupled with very limited matrilineal population structure. Confirming previous studies, our environmental niche models showed a decrease in available habitat during the Last Glacial Maximum, but we find no genetic signals of recent population declines in mitochondrial genomes despite both sustained habitat loss and a commercial whaling bottleneck. Our results illustrate the complex dynamics of baleen whale biogeography since the Holocene as well as the difficulty in detecting recent demographic bottlenecks from mitochondrial DNA sequences.
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Panigada, S., M. Zanardelli, S. Canese, and M. Jahoda. "How deep can baleen whales dive?" Marine Ecology Progress Series 187 (1999): 309–11. http://dx.doi.org/10.3354/meps187309.
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Piatt, JF, and DA Methven. "Threshold foraging behavior of baleen whales." Marine Ecology Progress Series 84 (1992): 205–10. http://dx.doi.org/10.3354/meps084205.
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Thomas, Peter O., Randall R. Reeves, and Robert L. Brownell. "Status of the world's baleen whales." Marine Mammal Science 32, no. 2 (2015): 682–734. http://dx.doi.org/10.1111/mms.12281.
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Corkeron, Peter J., and Richard C. Connor. "WHY DO BALEEN WHALES MIGRATE?1." Marine Mammal Science 15, no. 4 (1999): 1228–45. http://dx.doi.org/10.1111/j.1748-7692.1999.tb00887.x.
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Jackson, Jeremy. "On the evolution of baleen whales." Science 360, no. 6384 (2018): 44.1–44. http://dx.doi.org/10.1126/science.360.6384.44-a.
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Bianucci, Giovanni, Felix G. Marx, Alberto Collareta, et al. "Rise of the titans: baleen whales became giants earlier than thought." Biology Letters 15, no. 5 (2019): 20190175. http://dx.doi.org/10.1098/rsbl.2019.0175.
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Baleen whales (Mysticeti) are major ecosystem engineers, thanks to their enormous size and bulk filter feeding strategy. Their signature gigantism is thought to be a relatively recent phenomenon, resulting from a Plio-Pleistocene mode shift in their body size evolution. Here, we report the largest whale fossil ever described: an Early Pleistocene (1.5–1.25 Ma) blue whale from Italy with an estimated body length of up to 26 m. Macroevolutionary modelling taking into account this specimen, as well as additional material from the Miocene of Peru, reveals that the proposed mode shift occurred either somewhat earlier, or perhaps not at all. Large-sized mysticetes comparable to most extant species have existed since at least the Late Miocene, suggesting a long-term impact on global marine ecosystems.
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Hocking, David P., Felix G. Marx, Erich M. G. Fitzgerald, and Alistair R. Evans. "Ancient whales did not filter feed with their teeth." Biology Letters 13, no. 8 (2017): 20170348. http://dx.doi.org/10.1098/rsbl.2017.0348.
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The origin of baleen whales (Mysticeti), the largest animals on Earth, is closely tied to their signature filter-feeding strategy. Unlike their modern relatives, archaic whales possessed a well-developed, heterodont adult dentition. How these teeth were used, and what role their function and subsequent loss played in the emergence of filter feeding, is an enduring mystery. In particular, it has been suggested that elaborate tooth crowns may have enabled stem mysticetes to filter with their postcanine teeth in a manner analogous to living crabeater and leopard seals, thereby facilitating the transition to baleen-assisted filtering. Here we show that the teeth of archaic mysticetes are as sharp as those of terrestrial carnivorans, raptorial pinnipeds and archaeocetes, and thus were capable of capturing and processing prey. By contrast, the postcanine teeth of leopard and crabeater seals are markedly blunter, and clearly unsuited to raptorial feeding. Our results suggest that mysticetes never passed through a tooth-based filtration phase, and that the use of teeth and baleen in early whales was not functionally connected. Continued selection for tooth sharpness in archaic mysticetes is best explained by a feeding strategy that included both biting and suction, similar to that of most living pinnipeds and, probably, early toothed whales (Odontoceti).
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Kahane-Rapport, S. R., M. S. Savoca, D. E. Cade, et al. "Lunge filter feeding biomechanics constrain rorqual foraging ecology across scale." Journal of Experimental Biology 223, no. 20 (2020): jeb224196. http://dx.doi.org/10.1242/jeb.224196.
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ABSTRACTFundamental scaling relationships influence the physiology of vital rates, which in turn shape the ecology and evolution of organisms. For diving mammals, benefits conferred by large body size include reduced transport costs and enhanced breath-holding capacity, thereby increasing overall foraging efficiency. Rorqual whales feed by engulfing a large mass of prey-laden water at high speed and filtering it through baleen plates. However, as engulfment capacity increases with body length (engulfment volume∝body length3.57), the surface area of the baleen filter does not increase proportionally (baleen area∝body length1.82), and thus the filtration time of larger rorquals predictably increases as the baleen surface area must filter a disproportionally large amount of water. We predicted that filtration time should scale with body length to the power of 1.75 (filter time∝body length1.75). We tested this hypothesis on four rorqual species using multi-sensor tags with corresponding unoccupied aircraft systems-based body length estimates. We found that filter time scales with body length to the power of 1.79 (95% CI: 1.61–1.97). This result highlights a scale-dependent trade-off between engulfment capacity and baleen area that creates a biomechanical constraint to foraging through increased filtration time. Consequently, larger whales must target high-density prey patches commensurate to the gulp size to meet their increased energetic demands. If these optimal patches are absent, larger rorquals may experience reduced foraging efficiency compared with smaller whales if they do not match their engulfment capacity to the size of targeted prey aggregations.
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Lisney, Thomas J., and Shaun P. Collin. "Retinal Topography in Two Species of Baleen Whale (Cetacea: Mysticeti)." Brain, Behavior and Evolution 92, no. 3-4 (2018): 97–116. http://dx.doi.org/10.1159/000495285.
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Little is known about the visual systems of large baleen whales (Mysticeti: Cetacea). In this study, we investigate eye morphology and the topographic distribution of retinal ganglion cells (RGCs) in two species of mysticete, Bryde’s whale (Balaenoptera edeni) and the humpback whale (Megaptera novaeanglia). Both species have large eyes characterised by a thickened cornea, a heavily thickened sclera, a highly vascularised fibro-adipose bundle surrounding the optic nerve at the back of the eye, and a reflective blue-green tapetum fibrosum. Using stereology and retinal whole mounts, we estimate a total of 274,268 and 161,371 RGCs in the Bryde’s whale and humpback whale retinas, respectively. Both species have a similar retinal topography, consisting of nasal and temporal areas of high RGC density, suggesting that having higher visual acuity in the anterior and latero-caudal visual fields is particularly important in these animals. The temporal area is larger in both species and contains the peak RGC densities (160 cells mm–2 in the humpback whale and 200 cells mm–2 in Bryde’s whale). In the Bryde’s whale retina, the two high-density areas are connected by a weak centro-ventral visual streak, but such a specialisation is not evident in the humpback whale. Measurements of RGC soma area reveal that although the RGCs in both species vary substantially in size, RGC soma area is inversely proportional to RGC density, with cells in the nasal and temporal high-density areas being relatively more homogeneous in size compared to the RGCs in the central retina and the dorsal and ventral retinal periphery. Some of the RGCs were very large, with soma areas of over 2,000 µm2. Using peak RGC density and eye axial diameter (Bryde’s whale: 63.5 mm; humpback whale: 48.5 mm), we estimated the peak anatomical spatial resolving power in water to be 4.8 cycles/degree and 3.3 cycles/degree in the Bryde’s whale and the humpback whale, respectively. Overall, our findings for these two species are very similar to those reported for other species of cetaceans. This indicates that, irrespective of the significant differences in body size and shape, behavioural ecology and feeding strategy between mysticetes and odontocetes (toothed whales), cetacean eyes are adapted to vision in dim light and adhere to a common “bauplan” that evolved prior to the divergence of the two cetacean parvorders (Odontoceti and Mysticeti) over 30 million years ago.
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Whitehead, Hal, and J. E. Carscadden. "Predicting Inshore Whale Abundance — Whales and Capelin off the Newfoundland Coast." Canadian Journal of Fisheries and Aquatic Sciences 42, no. 5 (1985): 976–81. http://dx.doi.org/10.1139/f85-122.
Full textAbstract:
Inshore abundance of baleen whales along the Newfoundland coasts changed considerably during the period 1973–83. In particular, large numbers of humpbacks were present along the northeast coast each summer between 1977 and 1980. This influx led to entrapment of whales in fishing gear. Counts of humpback (Megaptera novaeangliae), finback (Balaenoptera physalus), and minke (Balaenoptera acutorostrata) whales during standard surveys along the coast are used as indices of inshore abundance, and are related to the year-class strengths of capelin (Mallotus villosus), their major food in the Newfoundland region. Whales are found inshore when there are few immature capelin offshore. Minke whale distributions seem more closely related to the abundance of 1- to 2-yr-old, immature capelin, but humpback and finback whales are found inshore with low abundances of 2- to 3-yr-old, mainly immature capelin. We suggest that estimates of capelin year-class strength predicted from abiotic variables can be used to predict inshore whale abundance, at least 1 yr in advance. The extreme influx of humpbacks of the late 1970s is unlikely to recur in the short term. The analysis suggests that finback populations in the area are declining.