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The Southern Ocean ecosystem has undergone extensive changes in the past two centuries driven by industrial sealing and whaling, climate change and commercial fishing. However, following the end of commercial whaling, some populations of whales in this region are recovering. Baleen whales are reliant on Antarctic krill, which is also the largest Southern Ocean fishery. Since 1993, krill catch has increased fourfold, buoyed by nutritional supplement and aquaculture industries. In this Perspective, we approximate baleen whale consumption of Antarctic krill before and after whaling to examine if the ecosystem can support both humans and whales as krill predators. Our back-of-the-envelope calculations suggest that current krill biomass cannot support both an expanding krill fishery and the recovery of whale populations to pre-whaling sizes, highlighting an emerging human-wildlife conflict. We then provide recommendations for enhancing sustainability in this region by reducing encounters with whales and bolstering the krill population. The Southern Ocean ecosystem is recovering from 20th-century industrial whaling, while the krill fishery in this region has grown rapidly and may expand further, driven by demand for supplements and aquaculture feed. This Perspective discusses how current krill biomass is unlikely to support both a growing krill fishery and rebounding whale populations in the Southern Ocean. [ABSTRACT FROM AUTHOR]

When, where, and what predators prey upon salmon is fundamental to understanding their mortality in a given region. We reviewed the available information about predators of three Japanese Pacific salmon species throughout their life history: chum salmon Oncorhynchus keta, pink salmon O. gorbuscha, and masu salmon O. masou. Thirteen fish species, including seven salmonid species, and three avian species, such as great cormorant Phalacrocorax carbo, have been described as predators of fry/juvenile salmon in rivers. Predators of fry/juveniles in estuarine–coastal areas have been relatively well investigated and include 15 fish species, including young masu salmon, and five avian species, such as rhinoceros auklet Cerorhinca monocerata. Four large fish species, such as salmon shark Lamna ditropis, one baleen whale species, and pinnipeds are reported predators of subadults in the open sea. In the sea around Japan, including the Pacific, the Sea of Okhotsk, and the Japan Sea, we found evidence of predation on subadults, adults, unknown life-stage salmon by four pinniped species and three species of baleen and toothed whales. Adults returning to rivers were preyed upon by two mammal species including brown bear Ursus arctos and two raptor species. We also identified information gaps for specific predators by region and life stage. Collaborating with non-researchers to obtain observation records of predation on salmon is one method that could efficiently expand our knowledge of local predators. We further suggest using the information from our review to incorporate predation effects as well as environmental factors in models examining salmon stock fluctuation mechanisms. [ABSTRACT FROM AUTHOR]

The relative importance of various sensory modalities can shift in response to evolutionary transitions, resulting in changes to underlying gene families encoding their reception systems. The rapid birth‐and‐death process underlying the evolution of the large olfactory receptor (OR) gene family has accelerated genomic‐level change for the sense of smell in particular. The transition from the land to sea in marine mammals is an attractive model for understanding the influence of habitat shifts on sensory systems, with the retained OR repertoire of baleen whales contrasting with its loss in toothed whales. In this study, we examine to what extent the transition from a terrestrial to a marine environment has influenced the evolution of baleen whale OR repertoires. We developed Gene Mining Pipeline (GMPipe) (https://github.com/AprilJauhal/GMPipe), which can accurately identify large numbers of candidate OR genes. GMPipe identified 707 OR sequences from eight baleen whale species. These repertoires exhibited distinct family count distributions compared to terrestrial mammals, including signs of relative expansion in families OR10, OR11 and OR13. While many receptors have been lost or show signs of random drift in baleen whales, others exhibit signs of evolving under purifying or positive selection. Over 85% of OR genes could be sorted into orthologous groups of sequences containing at least four homologous sequences. Many of these groups, particularly from family OR10, presented signs of relative expansion and purifying selective pressure. Overall, our results suggest that the relatively small size of baleen whale OR repertoires result from specialisation to novel olfactory landscapes, as opposed to random drift. [ABSTRACT FROM AUTHOR]

Foraging efficiency is key to animal fitness. Consequently, animals evolved a variety of kinematic, morphological, physiological, and behavioral adaptations for efficient locomotion to reduce energy expenditure while moving to find, capture, and consume prey. Often suited to specific habitat and prey types, these adaptations correspond to the terrain or substrate the animal moves through. In aquatic systems, adaptations focus on overcoming drag, buoyancy, and hydrostatic forces. Buoyancy both benefits and hinders diving animals; in particular, shallow divers constantly contend with the costs of overcoming buoyancy to dive and maintain position. Pacific Coast Feeding Group (PCFG) gray whales forage in shallow habitats where they work against buoyancy to dive and feed using various foraging tactics. Bubble blasts (underwater exhalations) have been observed during several foraging tactics performed by PCFG whales. As exhalations aid buoyancy regulation in other diving animals, we hypothesize that bubble blasts are performed by longer, more buoyant whales in shallower water and that bubble blasts increase dive duration while accounting for size and tactic. We test our hypotheses using Bayesian linear mixed effects models and a 7‐year dataset of drone footage containing concurrent individual morphological and behavioral data. We find that while headstanding – a stationary, head‐down tactic – bubble blasts are performed by longer, more buoyant whales and extend the dive duration, whereas whales using forward‐swimming tactics are less likely to bubble blast. Our results suggest that PCFG gray whales may use bubble blasts as a behavioral adaption to mitigate the cost of energetically expensive tactics in their shallow habitat foraging niche. [ABSTRACT FROM AUTHOR]

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic‐endemic prey.We assessed diet and distribution of ECA killer whales using bulk and compound‐specific stable isotope analysis (CSIA) of amino acids (AA) of 54 skin biopsies collected from 2009 to 2020 around Baffin Island, Canada.Bulk ECA killer whale skin δ15N and δ13C values did not overlap with potential Arctic prey after adjustment for trophic discrimination, and instead reflected foraging history in the North Atlantic prior to their arrival in the ECA. Adjusted killer whale stable isotope (SI) values primarily overlapped with several species of North Atlantic baleen whales or tuna. Amino acid (AA)‐specific δ15N values indicated the ECA killer whales fed primarily on marine mammals, having similar glutamic acid δ15N–phenylalanine δ15N (δ15NGlx‐Phe) and threonine δ15N (δ15NThr) as mammal‐eating killer whales from the eastern North Pacific (ENP) that served as a comparative framework. However, one ECA whale grouped with the fish‐eating ENP ecotype based δ15NThr.Distinctive essential AA δ13C of ECA killer whale groups, along with bulk SI similarity to killer whales from different regions of the North Atlantic, indicates different populations converge in Arctic waters from a broad source area. Generalist diet and long‐distance dispersal capacity favour range expansions, and integration of these insights will be critical for assessing ecological impacts of increasing killer whale predation pressure on Arctic‐endemic species. [ABSTRACT FROM AUTHOR]

Individual specialization may occur relative to diet, behaviour or spatial distribution, potentially leading to differential resource and space use within a population. While specializations have been documented across many animal populations, the underlaying causes of individual specialization (e.g. morphology, age or sex) are not always identified. Causes of specialization can be especially challenging to uncover for large, long-lived marine animals. We used a Bayesian multilevel, multinomial logistic regression model to study the relationships between grey whale, Eschrichtius robustus , use of foraging tactics and morphology (body length and condition), while accounting for habitat characteristics and individual variation in tactic use. The model was informed by a 7-year longitudinal data set of concurrent morphology and foraging behaviour collected using drones. We found evidence of an ontogenetic shift in the use of foraging tactics associated with body length (a proxy for age). Individual specialization in behaviour was also associated with water depth and habitat. After accounting for the effects of these covariates, there was some residual individual level variation in the use of different foraging tactics. Our findings demonstrate variation in resource and habitat use within a baleen whale population at the individual level relative to body length and habitat, suggesting that individual spatial distribution and access to prey may vary by age class. Our results can be applied to investigate whether juveniles and adults differ in their foraging success and resilience to stressors. • We used drones to measure behaviour and morphology of eastern grey whales. • Whale foraging behaviours were associated with morphology and habitat type. • Different foraging tactics were associated with different depths and habitat types. • Whales switched foraging tactics as they grew in length. • Morphology affected habitat and prey accessibility and consequently tactic use. [ABSTRACT FROM AUTHOR]

Baleen whales are key consumers in marine ecosystems and can serve as ecosystem sentinels. Body condition, defined as an individual’s energy stores relative to its structural size, can provide a useful proxy for health in baleen whales. As capital breeders, important life history events in baleen whales such as seasonal migrations and reproduction depend on having sufficient energy stores. Spatiotemporal variability of body condition of baleen whales can reflect differences in energy accumulated during the foraging season. Here we assess and compare the body condition and mass of humpback whales (Megaptera novaeangliae) across four different foraging areas from the West Indies distinct population segment in the Northwest Atlantic. Morphometric measurements of humpback whales were obtained using unoccupied aerial systems (UAS, or drones) from the New York Bight, the Gulf of Maine, Iceland, and Greenland. Uncertainty in morphometric estimates was incorporated and propagated using a bootstrapping approach. Measurements were used to estimate body volume and calculate a body condition index (BCI) for each individual whale. Since body mass is a key parameter for understanding animal physiology and bioenergetics, we further compared whale body mass to body size between foraging areas by converting body volume to body mass using estimates of tissue density from tagging studies. BCI showed significant differences between foraging areas with a large effect size (ANCOVA: mean η² = 0.168; all p< 0.001) when incorporating day of year and year as covariates. Humpback whales in the Gulf of Maine showed significantly higher BCI than those in the New York Bight, Iceland, and Greenland. Standardized Major Axis (SMA) regressions comparing log-log relationships of both body volume and body mass, respectively, to total length reinforced these results. Humpback whales in the Gulf of Maine showed significantly higher elevation in the SMAs than those in the other study regions (p<0.001), implying that humpback whales foraging in the Gulf of Maine accumulated greater energy reserves for a given body size. Estimates of body mass indicate that for a given body length, humpback whales in the Gulf of Maine have an 18% greater body mass than those in the New York Bight, Iceland, or Greenland. Regional differences in prey availability or anthropogenic threats could contribute to the observed patterns in body condition. Our findings highlight the importance of regional environmental factors to the nutritional health of baleen whales. [ABSTRACT FROM AUTHOR]

Knowledge about species-specific hearing is vital to assessing how anthropogenic noise impacts marine mammals. Unfortunately, no empirical audiogram exists for any mysticete whale. We therefore developed a catch-and-release method to assess hearing in a small mysticete, the minke whale (Balaenoptera acutorostrata). Stationary lead nets were placed to intercept migratory routes and direct the whales into an ocean basin enclosed by nets and islets, while another net was pulled across the entrance once a whale entered the basin. The minke whales were then slowly corralled into a modified aquaculture pen using a net suspended between two boats. Subsequently, the water volume available to the whales was gradually reduced by raising the pen net by hand until the whales were secured in a “hammock” between the floating pen ring and a raft. From the raft, researchers could access the whales to monitor their health, apply instruments for hearing tests, or perform other research objectives, and then attach tags to monitor the movements and diving behavior of the whale post-release. The method is a slow and controlled procedure, allowing continuous monitoring and quick release of the whales, if needed. In the first three field seasons employing the method, three minke whales were caught for research procedures. Initial hearing measurements using auditory evoked potentials were successfully completed. After release, the whales resumed migration, and dive behavior was considered normal. Our observations demonstrated that minke whales can be guided safely via moored net barriers, corralled into an aquaculture pen, and safely handled for research purposes, before being released back into the wild. [ABSTRACT FROM AUTHOR]

This article discusses observations of killer whale attacks on sei and fin whales in the Magellanic Sub-Antarctic Waters of Chile. The attacks occurred between March 2020 and April 2021 and resulted in the death of the whales. The researchers were able to identify one female killer whale involved in three of the attacks, which is relatively rare. The study emphasizes the need for further research on the trophic ecology and dietary plasticity of killer whales in the area. Additionally, a collection of articles and studies on killer whale behavior, diet, and interactions with other marine species is provided, offering valuable insights for researchers and library patrons interested in understanding the behavior and ecological role of killer whales in diverse marine ecosystems. [Extracted from the article]

Humpback whales in Bermuda have been observed engaging in a unique behavior of expanding their oral pouches and rubbing them against the seafloor. This behavior is believed to be a method of skin maintenance in areas where barnacles and whale lice congregate. The whales were observed swimming together, often in pairs, and descending into sand holes to rub their expanded pouches against the bottom. This behavior is different from feeding and may serve as a way for the whales to exfoliate and clean hard-to-reach areas of their bodies. Further research is needed to fully understand this behavior. [Extracted from the article]

This article discusses the first documented observation of sexual behavior between two male humpback whales. The researchers observed one emaciated whale with a jaw injury being pursued and penetrated by another whale, who held it in place with its pectoral fins. While nonreproductive sexual behavior is common in many species, humpback whale sexual behavior remains largely undescribed. The significance and contexts of these behaviors in humpback whale social interactions require further study. [Extracted from the article]

The available data on occurrence patterns of cetaceans in the Red Sea area of the Kingdom of Saudi Arabia is very limited. The dearth of information is of pressing conservation concern as the coastline is undergoing rapid development as part of the Kingdom's effort to diversify its national economy. To understand how these developments will impact cetaceans in the region, the first large‐scale acoustic and visual survey in the Kingdom's part of the Gulf of Aqaba and the northeastern Red Sea was undertaken in 2020. The results of the acoustic surveys reveal 3.6 encounters per 100 km of track line of odontocete species with variable distribution across the study area. No baleen whale vocalizations were detected. Through visual surveys, five odontocete species were identified within the study area: Tursiops truncatus, T. aduncus, Stenella attenuata, S. longirostris, and two opportunistic sightings of a single Grampus griseus. [ABSTRACT FROM AUTHOR]

The earliest Miocene (Aquitanian, 23–20 Ma) remains a critically under-sampled 'dark age' in cetacean evolution. This is especially true of baleen whales (mysticetes), Aquitanian specimens of which remain almost entirely unknown. Across the globe, the nature of the cetacean fossil record radically shifts at the Oligocene-Miocene boundary, with mysticetes and some archaic odontocete lineages suddenly disappearing despite the availability of cetacean-bearing rock units. New Zealand is the only place worldwide where this change is not readily apparent, with baleen whales apparently persisting into the earliest Miocene. Whether this is a genuine pattern has so far remained obscured by a lack of biostratigraphic resolution associated with the Oligo-Miocene boundary. Here, we report 23 new strontium (87Sr/86Sr) dates from Lentipecten shells associated with 16 mysticete and seven odontocete specimens, respectively. Of these, eight fall within the Early Miocene and seven – including five mysticetes – specifically within the Aquitanian. Our findings confirm the unique nature and global importance of the cetacean fossil record from New Zealand, and provide a foundation for investigations into the causes and effects of the Early Miocene cetacean 'dark age'. [ABSTRACT FROM AUTHOR]

Eomysticetidae are a clade of early diverging functionally toothless, longirostrine and likely baleen-bearing stem mysticete whales. Eomysticetid fossils are rare but known worldwide from Oligocene strata. The richest assemblage of eomysticetids has been uncovered in New Zealand from the Kokoamu Greensand and Otekaike Limestone (North Otago and South Canterbury regions, South Island). This includes some of the largest known eomysticetids, Tokarahia kauaeroa and Tokarahia lophocephalus, some older and more archaic forms such as Matapanui waihao, the fragmentary Tohoraata raekohao and Tohoraata waitakiensis, and the well-known Waharoa ruwhenua represented by several well-preserved skulls and mandibles of adults and juveniles. Studies of these New Zealand fossils strongly indicates monophyly of Eomysticetidae and suggest possible skim feeding behaviour, possession of non-functional teeth and baleen, extreme rostral lengthening during growth and peramorphic evolution, rostral kinesis, use of Zealandia as a calving ground, and probable extinction at or near the Oligo-Miocene boundary. [ABSTRACT FROM AUTHOR]

Recent research on mysticete fossils from the Late Eocene and Oligocene has revolutionised our understanding of the diversity and evolutionary scenarios for early baleen whales. For example, aetiocetids are a possible, though controversial, lineage that bridges the gap between the toothed and baleen-bearing mysticetes, and eomysticetids show a further transitional step towards the baleen-bearing status, with the presence of non-functional dentition in adults. However, information about the origin of crown mysticetes, including the most recent common ancestor of all extant lineages and its descendants, is critical to further understanding the evolution of baleen whales. The phylogenetic positions of the Oligocene Toipahautea, Whakakai, Horopeta, and Mauicetus from New Zealand remain unresolved and problematic, but all four genera show a close relationship with crown mysticetes. The original and subsequent cladistic analyses have consistently revealed a sister relationship between the Toipahautea-to-Mauicetus grade and crown mysticetes, and Horopeta has been placed close to the cetotheriids within the crown group. This review aims to stimulate more research on this topic by elucidating the origin of crown mysticetes, which likely experienced a poorly known radiation event during the Oligocene that established the modern lineages. [ABSTRACT FROM AUTHOR]

The sei whale (Balaenoptera borealis) is an important species among baleen whales in the North Pacific and plays a significant role in the ecosystem. Despite the importance of this species, information regarding its migration patterns and breeding locations remains limited. To enhance the understanding of the phenology of North Pacific sei whales, we deployed satellite-monitored tags on these whales in the western and central North Pacific from 2017 to 2023. We fitted 55 sei whale tracks to a state-space model to describe the whales' seasonal movements at feeding grounds and their migratory behavior. The whales typically leave their feeding grounds between November and December, with migration pathways extending from off Japan to the west of the Hawaiian Islands. These southward transits converge in the waters of the Marshall Islands and north of Micronesia between 20° N and 7° N, which appear to be breeding grounds. After a brief stay at these breeding grounds, the whales migrate northward from January to February, reaching their feeding grounds around 30°N by March. To the best of our knowledge, this is the first study to present the phenology of feeding and breeding seasons and the migration pattern of North Pacific sei whales. [ABSTRACT FROM AUTHOR]

While rhythm can facilitate and enhance many aspects of behavior, its evolutionary trajectory in vocal communication systems remains enigmatic. We can trace evolutionary processes by investigating rhythmic abilities in different species, but research to date has largely focused on songbirds and primates. We present evidence that cetaceans--whales, dolphins, and porpoises--are a missing piece of the puzzle for understanding why rhythm evolved in vocal communication systems. Cetaceans not only produce rhythmic vocalizations but also exhibit behaviors known or thought to play a role in the evolution of different features of rhythm. These behaviors include vocal learning abilities, advanced breathing control, sexually selected vocal displays, prolonged mother-infant bonds, and behavioral synchronization. The untapped comparative potential of cetaceans is further enhanced by high interspecific diversity, which generates natural ranges of vocal and social complexity for investigating various evolutionary hypotheses. We show that rhythm (particularly isochronous rhythm, when sounds are equally spaced in time) is prevalent in cetacean vocalizations but is used in different contexts by baleen and toothed whales. We also highlight key questions and research areas that will enhance understanding of vocal rhythms across taxa. By coupling an infraorder-level taxonomic assessment of vocal rhythm production with comparisons to other species, we illustrate how broadly comparative research can contribute to a more nuanced understanding of the prevalence, evolution, and possible functions of rhythm in animal communication. [ABSTRACT FROM AUTHOR]

The Salish Sea supports several baleen whale species, including humpback (Megaptera novaeangliae), gray (Eschrichtius robustus) and minke whales (Balaenoptera acutorostrata). With the exception of minke whales, these species were decimated by commercial whaling in the 1900s. Because recovery of these populations is monitored on broad spatial scales determined by stocks or populations, their use of the Salish Sea ecosystem is not well documented or understood. We collated 17,436 opportunistic sighting reports to assess patterns in mysticete presence and distribution in the Salish Sea (1976-2019). We used the proportion of sightings for each species and spatial models targeting comparisons between species to limit the influence of spatio-temporal variation in reporting efforts. Humpback whale sightings have increased dramatically since the late 2000s, mirroring population-wide increases and suggesting a renewed use of historically important feeding areas. Gray whale sightings increased most notably at two distinct times (1989, 2017), both of which align with periods of high mortality experienced by the delisted Eastern North Pacific stock of gray whales and may reflect individuals straying from their migration routes. Sightings of minke whales remained relatively stable over this study period and were likely driven by a group of 30-40 individuals that forage off shallow banks and bathymetrically complex habitats around the San Juan Archipelago. Though it can be difficult to separate the bias that accompanies public sightings databases, citizen science efforts are invaluable for monitoring the recovery of rebounding populations and can illuminate longitudinal patterns that would otherwise go unnoticed. [ABSTRACT FROM AUTHOR]

Context: Humpback whale (Megaptera novaeangliae) populations have been recovering from whaling but are now facing threats from changing food availability due to ocean warming and changes in habitat suitability. There is uncertainty over whether opportunistic observations can produce reliable species distribution models (SDMs) and adequately inform conservation management. Aims: To compare SDMs for humpback whales in the Great Barrier Reef Marine Park based on different opportunistic sightings datasets and evaluate the impact different sources of opportunistic data have on our understanding of humpback whale habitat relationships. Methods: Maximum entropy modelling (Maxent) was used to create predictive models for humpback whale distributions. Sighting data from citizen science and opportunistic observations from various other databases were used. Models were compared to evaluate disparities and predictive capabilities. Key results: Distinct environmental variables [bathymetry, distance to the coast] were identified as the most relevant for each SDM. The best-fitting model diverged from an existing model, with humpback whale distribution predicted to be closer to shore. Areas with the highest habitat suitability were concentrated in the north-eastern coastal region across all models developed in this study. Conclusions: This study demonstrates that, with careful application and consideration, citizen science data can enhance our understanding of humpback whale distributions and contribute to their conservation. The research underlines the importance of embracing diverse data sources in SDM, despite the challenges posed by opportunistic data. Implications: The study provides valuable insights for conservation management and informs strategies to protect humpback whale populations in changing environmental conditions. Understanding the habitat relationships of humpback whales in the Great Barrier Reef is key for conservation. This study compares species distribution models based on different opportunistic sightings datasets, revealing distinct significance of environmental factors. The findings inform strategies to protect humpback whale populations in the face of changing environmental conditions. [ABSTRACT FROM AUTHOR]

Changes in body size have been documented across taxa in response to human activities and climate change. Body size influences many aspects of an individual's physiology, behavior, and ecology, ultimately affecting life history performance and resilience to stressors. In this study, we developed an analytical approach to model individual growth patterns using aerial imagery collected via drones, which can be used to investigate shifts in body size in a population and the associated drivers. We applied the method to a large morphological dataset of gray whales (Eschrichtius robustus) using a distinct foraging ground along the NE Pacific coast, and found that the asymptotic length of these whales has declined since around the year 2000 at an average rate of 0.05–0.12 m/y. The decline has been stronger in females, which are estimated to be now comparable in size to males, minimizing sexual dimorphism. We show that the decline in asymptotic length is correlated with two oceanographic metrics acting as proxies of habitat quality at different scales: the mean Pacific Decadal Oscillation index, and the mean ratio between upwelling intensity in a season and the number of relaxation events. These results suggest that the decline in gray whale body size may represent a plastic response to changing environmental conditions. Decreasing body size could have cascading effects on the population's demography, ability to adjust to environmental changes, and ecological influence on the structure of their community. This finding adds to the mounting evidence that body size is shrinking in several marine populations in association with climate change and other anthropogenic stressors. Our modeling approach is broadly applicable across multiple systems where morphological data on megafauna are collected using drones. [ABSTRACT FROM AUTHOR]

Fin whale song is a ubiquitous low-frequency pulsing that has been recorded in every ocean basin. In recent years, the complexity of fin whale song has been realized. In the North Atlantic, this song is made up of two low-frequency note types (A and B notes) and one higher-frequency note type (upsweeps). The A and B notes are produced with both singlet and doublet inter-note intervals. These song patterns are interwoven throughout an individual's song and have been observed to shift over time, both gradually and suddenly. Like many baleen whales, the population size of fin whales is poorly defined. Passive acoustic monitoring has been suggested as a way to estimate abundance if a cue rate or calling rate can be determined. In this study, we used recordings from 119 fin whale tracks from 2013-2023 generated from passive acoustic recorders in the North Atlantic to define fin whale song patterns in this ocean basin, identify changes in these song patterns over time, and calculate cue rates. The fin whales recorded sang in 4 distinct patterns. Inter-note intervals were 25 s for A-A singlets, 13 s for B-B singlets, 12/20 s for B-B doublets, and 10/11 s for A-B doublets. B-B doublet inter-note intervals significantly increased from May 2019-April 2023 and A-B inter-note intervals showed an intra-annual increasing trend that reset each summer. Fin whale song in the North Atlantic also often includes higher frequency upsweep notes immediately prior to B notes. While A and B note peak frequency was steady over these years, upsweep peak frequency significantly decreased, continuing a similar trend that has been observed over 30 years. Despite these changes, the dominant song pattern remained consistent and cue rate for actively singing whales was relatively stable, which is in contrast to patterns observed in the North Pacific. Many of these nuances in fin whale singing behavior are newly described herein, and these findings are vital for monitoring baseline behavior, behavioral trends over time, and ultimately estimating abundance of a poorly understood species. [ABSTRACT FROM AUTHOR]

Introduction: The oceanic waters around the Azores host a high diversity of cetaceans, with 28 species of toothed and baleen whales present year-round or seasonally. This high cetacean biodiversity likely plays an important role in the structure, functioning and productivity of the ecosystem, and may increase trophic redundancy, thus contributing to food web resilience to disturbances. Methods: Here we used stable isotope (γ13C and γ15N) analysis to characterize trophic niches, assess niche overlap, describe the trophic structure and discuss potential redundancy in the cetacean community. Using 407 samples from 12 species, we estimated Standard Ellipse Areas and overlaps between species and used a hierarchical clustering analysis to identify trophic guilds. Results and discussion: γ13C and γ15N values ranged from -20.53 to -15.46‰ and from 7.78 to 14.41‰ respectively, suggesting the use of diverse habitats and resources among cetacean species. Clustering analysis revealed that species were grouped into four trophic guilds, segregated mainly by trophic position (TP): a low-TP guild with three zooplanktivore baleen whales, a mid-TP guild with micronektivores, a high-TP guild with micronekton and nekton consumers, and a cluster with only Pseudorca crassidens. There was significant isotopic niche overlap between one pair of species within each guild, indicating some potential for trophic redundancy in the community. Yet, these pairs also showed some form of spatial or temporal partitioning, suggesting that mechanisms promoting species coexistence could play a key role in structuring the cetacean community in the region and in its ecological role. [ABSTRACT FROM AUTHOR]

Background: The life cycle of most baleen whales involves annual migrations from low-latitude breeding grounds to high latitude feeding grounds. In most species, these migrations are traditionally considered to be carried out according to information acquired through vertical social learning during the first months of life and made individually. However, some recent studies have suggested a more complex scenario, particularly for the species of the Balaenoptera genus. Methods: Here, we studied the variation of δ15N and δ13C values along the growth axis of the baleen plate from 24 fin whales feeding off western Iceland to delve into their pattern of movements and to identify potential associations between individuals. The segment of baleen plate analyzed informed about at least two complete migratory cycles. We performed cluster analyses through two different methodologies and, whenever possible, we genotyped 20 microsatellite loci to determine potential existence of kinship. Results: Results of the of δ15N and δ13C values agree with a dispersion strategy in the winter breeding grounds. However, and despite the overall large variability, several pairs or groups of individuals with no kinship showed highly similar isotopic patterns for two consecutive years for both δ15N and δ13C values. Conclusions: Our results suggest that, notably, some whales without kinship share the same migratory regime and destinations. We hypothesize that this could reflect either: (i) the sharing of particularly beneficial migratory regimes, and/or (ii) long-term association between individuals. [ABSTRACT FROM AUTHOR]

Chromosome instability, a hallmark of lung cancer, is a driving mechanism for hexavalent chromium [Cr(VI)] carcinogenesis in humans. Cr(VI) induces structural and numerical chromosome instability in human lung cells by inducing DNA double-strand breaks and inhibiting homologous recombination repair and causing spindle assembly checkpoint (SAC) bypass and centrosome amplification. Great whales are long-lived species with long-term exposures to Cr(VI) and accumulate Cr in their tissue, but exhibit a low incidence of cancer. Data show Cr(VI) induces fewer chromosome aberrations in whale cells after acute Cr(VI) exposure suggesting whale cells can evade Cr(VI)-induced chromosome instability. However, it is unknown if whales can evade Cr(VI)-induced chromosome instability. Thus, we tested the hypothesis that whale cells resist Cr(VI)-induced loss of homologous recombination repair activity and increased SAC bypass and centrosome amplification. We found Cr(VI) induces similar amounts of DNA double-strand breaks after acute (24 h) and prolonged (120 h) exposures in whale lung cells, but does not inhibit homologous recombination repair, SAC bypass, or centrosome amplification, and does not induce chromosome instability. These data indicate whale lung cells resist Cr(VI)-induced chromosome instability, the major driver for Cr(VI) carcinogenesis at a cellular level, consistent with observations that whales are resistant to cancer. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Top krill predators such as the Antarctic minke whale (AMW) serve a vital role within the fragile Antarctic sea-ice ecosystem. They are an abundant krill specialist, but their ecological role in the Antarctic remains poorly understood due to their cryptic behavior and remote habitat. It is therefore crucial to develop a baseline understanding of their basic social and foraging ecology. This study uses animal-borne camera tags to quantitatively explore these critical ecological aspects. Twenty-eight tags were deployed on AMW between 2018 and 2019 in Andvord and Paradise Bays around the Western Antarctic Peninsula. Tag data were analyzed with respect to diving, foraging, and social behavior. Results suggest the presence of loose fission-fusion sociality, with individuals forming short-term associations in 60.6% of cases including both foraging and non-foraging contexts. Socializing was significantly more common for larger individuals and resulted in a significant decrease in foraging rates for both shallow (< 30 m) and deep (> 30 m) dives. There were 12 instances of simultaneously tagged individuals that associated with one another in pairs or trios, displaying synchronized spatial movement and diving behavior. These data illustrated the use of group foraging strategies, with high incidence of synchronized foraging dives (67.5% of associated dives) and lunges (64% of associated lunges). Our results provide clear baseline information on AMW sociality and group foraging, which will help direct future studies for more targeted work. This study will improve our ability to understand the relationship between Antarctic species and their environment as climate change continues to alter the ecosystem landscape. Significance: Baseline information on sociality is thus key to understanding broader species ecology, which is especially important for keystone species. Our study is the first to directly provide these foundational insights for AMW, a common krill predator in the Antarctic sea-ice ecosystem. Individuals displayed short-term associations in a fission-fusion social structure similar to other baleen whale species, and socializing was associated with both larger individuals and lower foraging rates. In simultaneous tag deployments, tagged individuals frequently associated with one another and displayed synchronized diving and foraging behavior. Our results suggest that sociality may be more important to minke whale ecology than previously thought. These results provide necessary baseline information for more targeted ecological questions, such as the benefit of group foraging or how such precise synchrony might be coordinated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In coastal British Columbia, Canada, marine megafauna such as humpback whales (Megaptera novaeangliae) and fin whales (Balaenoptera physalus velifera) have been subject to a history of exploitation and near extirpation. While their populations have been in recovery, significant threats are posed to these vulnerable species by proposed natural resource ventures in this region, in addition to the compounding effects of anthropogenic climate change. Genetic tools play a vital role in informing conservation efforts, but the associated collection of tissue biopsy samples can be challenging for the investigators and disruptive to the ongoing behaviour of the targeted whales. Here, we evaluate a minimally intrusive approach based on collecting exhaled breath condensate, or respiratory ‘blow’ samples, from baleen whales using an unoccupied aerial system (UAS), within Gitga'at First Nation territory for conservation genetics. Minimal behavioural responses to the sampling technique were observed, with no response detected 87% of the time (of 112 UAS deployments). DNA from whale blow (n = 88 samples) was extracted, and DNA profiles consisting of 10 nuclear microsatellite loci, sex identification and mitochondrial (mt) DNA haplotypes were constructed. An average of 7.5 microsatellite loci per individual were successfully genotyped. The success rates for mtDNA and sex assignment were 80% and 89% respectively. Thus, this minimally intrusive sampling method can be used to describe genetic diversity and generate genetic profiles for individual identification. The results of this research demonstrate the potential of UAS‐collected whale blow for conservation genetics from a remote location. [ABSTRACT FROM AUTHOR]

Baleen whales (Mysticeti) possess the necessary anatomical structures and genetic elements for olfaction. Nevertheless, the olfactory receptor gene (OR) repertoire has undergone substantial degeneration in the cetacean lineage following the divergence of the Artiodactyla and Cetacea. The functionality of highly degenerated mysticete ORs within their olfactory epithelium remains unknown. In this study, we extracted total RNA from the nasal mucosae of common minke whales (Balaenoptera acutorostrata) to investigate ORs' localized expression. All three sections of the mucosae examined in the nasal chamber displayed comparable histological structure. However, the posterior portion of the frontoturbinal region exhibited notably high OR expression. Neither the olfactory bulb nor the external skin exhibited the expression of these genes. Although this species possesses four intact non-class-2 ORs, all the ORs expressed in the nasal mucosae belong to class-2, implying the loss of aversion to specific odorants. These anatomical and genomic analyses suggest that ORs are still responsible for olfaction within the nasal region of baleen whales, enabling them to detect desirable scents such as prey and potential mating partners. [ABSTRACT FROM AUTHOR]

This article explores the cultural evolution of humpback whale songs in the South Atlantic, specifically focusing on changes observed in Brazil between 2017 and 2018. The study reveals a significant shift in the complexity of the songs, suggesting a cultural revolution within the humpback whale population. The authors propose that these revolutions are a result of cultural exchange between different populations during the nonbreeding season, facilitated by the lack of physical barriers in the Southern Hemisphere. The research emphasizes the importance of acoustic interactions in understanding the dynamics of humpback whale songs and highlights the need for further study in this area. [Extracted from the article]

This article reports the first direct observation of a successful southern right whale birth in South African coastal waters. Southern right whale females typically migrate to coastal areas in South Africa to give birth and nurse their young. The calving season extends from late June to late October, with a peak in August. Despite long-term research efforts, very little is known about the birthing event in southern right whales. The article describes the observation of a lone southern right whale performing unique behaviors, followed by the birth of a calf. The mother did not assist the calf immediately after birth, which is consistent with behavior observed in other successful cetacean births. The article highlights the value of opportunistic data and the need for further research to improve our understanding of cetacean behavior and ecology. [Extracted from the article]

The establishment of marine protected areas (MPAs) for cetaceans is an important strategy to mitigate human disturbance and protect biodiversity. Despite abundant cetacean species, there are only a few MPAs dedicated to cetacean conservation in China, all of which are for inshore dolphins. Bryde's whales, the only nearshore baleen whale population in mainland China, are conflicting with intensive human activities, yet an effective conservation strategy is lacking. This study used species distribution models to analyze distribution patterns and suitable habitats of Bryde's whales in the Beibu Gulf and proposes the first baleen whale MPA in China. Our results showed Bryde's whales have a seasonal distribution pattern in the Beibu Gulf, and that the waters around Weizhou Island and the southeastern coast of Vietnam were their core habitats. The seasonal nighttime light data indicated a negative relationship between the number of ship lights and Bryde's whale sightings and suggest that Bryde's whales might be threatened by fisheries. We proposed an MPA based on the results, suggesting that the waters within 20 km around Weizhou Island should be declared a protected area. Furthermore, we recommend that anthropogenic activities in the waters around Weizhou Island are better managed to reduce negative impacts on marine life. [ABSTRACT FROM AUTHOR]

This article presents a study on estimating tidal lung volumes (VT) in adult gray whales using audio and video recordings. The researchers used unmanned aerial systems (UAS) to monitor foraging whales in coastal waters and compared their findings to previous studies conducted in a winter breeding/calving lagoon. The results indicate that tidal lung volume can be estimated based on body length and exhalation duration. This method provides a new tool for understanding the metabolic rate and resource requirements of gray whales, as well as the impact of changing oceanographic conditions on their prey availability. [Extracted from the article]

Abstract Foraging efficiency is key to animal fitness. Consequently, animals evolved a variety of kinematic, morphological, physiological, and behavioral adaptations for efficient locomotion to reduce energy expenditure while moving to find, capture, and consume prey. Often suited to specific habitat and prey types, these adaptations correspond to the terrain or substrate the animal moves through. In aquatic systems, adaptations focus on overcoming drag, buoyancy, and hydrostatic forces. Buoyancy both benefits and hinders diving animals; in particular, shallow divers constantly contend with the costs of overcoming buoyancy to dive and maintain position. Pacific Coast Feeding Group (PCFG) gray whales forage in shallow habitats where they work against buoyancy to dive and feed using various foraging tactics. Bubble blasts (underwater exhalations) have been observed during several foraging tactics performed by PCFG whales. As exhalations aid buoyancy regulation in other diving animals, we hypothesize that bubble blasts are performed by longer, more buoyant whales in shallower water and that bubble blasts increase dive duration while accounting for size and tactic. We test our hypotheses using Bayesian linear mixed effects models and a 7‐year dataset of drone footage containing concurrent individual morphological and behavioral data. We find that while headstanding – a stationary, head‐down tactic – bubble blasts are performed by longer, more buoyant whales and extend the dive duration, whereas whales using forward‐swimming tactics are less likely to bubble blast. Our results suggest that PCFG gray whales may use bubble blasts as a behavioral adaption to mitigate the cost of energetically expensive tactics in their shallow habitat foraging niche.

Baleen whales are ecosystem sentinels of microplastic pollution. Research indicates that they likely ingest millions of anthropogenic microparticles per day when feeding. Their immense prey consumption and filter-feeding behavior put them at risk. However, the role of baleen, the oral filtering structure of mysticete whales, in this process has not been adequately addressed. Using actual baleen tissue from four whale species (fin, humpback, minke, and North Atlantic right) in flow tank experiments, we tested the capture rate of plastics of varying size, shape, and polymer type, as well as chemical residues leached by degraded plastics, all of which accumulated in the baleen filter. Expanded polystyrene foam was the most readily captured type of plastic, followed by fragments, fibers, nurdles, and spherical microbeads. Nurdle and microbead pellets were captured most readily by right whale baleen, and fragments were captured by humpback baleen. Although not all differences between polymer types were statistically significant, buoyant polymers were most often trapped by baleen. Plastics were captured by baleen sections from all regions of a full baleen rack, but were more readily captured by baleen from dorsal and posterior regions. Baleen–plastic interactions underlie various risks to whales, including filter clogging and damage, which may impede feeding. We posit that plastics pose a higher risk to some whale species due to a combination of factors, including filter porosity, diet, habitat and geographic distribution, and foraging ecology and behavior. Certain whale species in specific marine regions are of the greatest concern due to plastic abundance. It is not feasible to remove all plastic from the sea; most of what is there will continue to break into ever-smaller pieces. We suggest that higher priorities be accorded to lessening humans’ dependence on plastics, restricting entry points of plastics into the ocean, and developing biodegradable alternatives.

Abstract Many baleen whales are renowned for their acoustic communication. Under pristine conditions, this communication can plausibly occur across hundreds of kilometres. Frequent vocalisations may allow a dispersed migrating group to maintain contact, and therefore benefit from improved navigation via the “wisdom of the crowd”. Human activities have considerably inflated ocean noise levels. Here we develop a data-driven mathematical model to investigate how ambient noise levels may inhibit whale migration. Mathematical models allow us to simultaneously simulate collective whale migration behaviour, auditory cue detection, and noise propagation. Rising ambient noise levels are hypothesised to influence navigation through three mechanisms: (i) diminished communication space; (ii) reduced ability to hear external sound cues and; (iii) triggering noise avoidance behaviour. Comparing pristine and current soundscapes, we observe navigation impairment that ranges from mild (increased journey time) to extreme (failed navigation). Notably, the three mechanisms induce qualitatively different impacts on migration behaviour. We demonstrate the model’s potential predictive power, exploring the extent to which migration may be altered under future shipping and construction scenarios.

Cetotheriidae is a family of baleen whales that went nearly extinct during the Pleistocene (excluding Caperea marginata). For a long time, the Cetotheriidae family has been seen as a problematic clade, but in the past two decades there have been various studies trying to resolve the phylogeny of this group. In 1831, Alexandre Vandelli described three cetotheriid skulls, found during a gold exploration at Adiça beach (Portugal). These specimens constituted the first Portuguese vertebrate fossils ever published in the literature. Another skull was added to the "Vandelli skulls" by Jacinto Pedro Gomes, in 1914, during a survey of the Museu Nacional de História Natural collections without giving information on the origin of this skull. In 1941, Remington Kellogg states that one of the original "Vandelli skulls" is no longer present in the Museu Nacional de História Natural collections. Until today, there is no information on how, or exactly when, the fourth skull and one of the original three "Vandelli skulls" appeared and disappeared, respectively. Since their discovery, all the attempts to describe these specimens were not based on direct observations and no comprehensive phylogenetic analysis have included the three skulls. Here we provide a detailed anatomic description, a new phylogenetic analysis and a palaeoecological reconstruction of these specimens, clarifying their relationships within the Cetotheriidae family and fostering the importance of these historical specimens to the modern comprehension of fossil whale evolution. In addition, our results support that Cephalotropis nectus is a valid species with an emended diagnosis. We also concluded that two specimens belong to a new genus, forming two new fossil species (new combinations). [ABSTRACT FROM AUTHOR]

Gray whales (Eschrichtius robustus) evolved to suction feed on benthic invertebrates and typically do not consume adult fish. Yet, these whales are flexible foragers, occasionally skim feeding on planktonic invertebrates and rarely lunge feeding on fish, the latter according to anecdotal accounts. We documented the unusual phenomenon of multiple gray whales predating dense schools of anchovy over a sustained period (22 days) in June 2022 at Pacifica, California, in the Gulf of the Farallones. Analysis of 11,265 photos and 11 video clips (totaling 4 min 16 s) for behavior and whale identification resulted in a total of 165 foraging events by six identified gray whales. Attribution of foraging behavior to the most active individuals was achieved by matching left pectoral fins, visible during lateralized feeding behavior. Whales rolled onto their right sides in 96% of near-surface side-swimming bouts. Another behavior, first photographed here, was dynamic surface lunge feeding by one gray whale. Five gray whales interspersed fish feeding with benthic suction feeding evidenced by sediment streaming: prey type switching was executed rapidly, in less than 1 minute in several instances, the shortest intervals reported for a baleen whale. Similar results were obtained for foraging behavior switching (continuous side-swimming or intermittent lunging) in pursuit of fish. Four photo-identified Pacifica whales were sighted in San Francisco Bay/Gulf of the Farallones, one of which was also matched to the Pacific Coast Feeding Group. Such local and regional connections warrant efforts to determine whether gray whales use this area as a migratory stopover site or for summer foraging, or both. Our observations confirm gray whale behavioral plasticity and opportunistic exploitation of food resources in mid-latitudes, which may enhance their resilience to climate change. [ABSTRACT FROM AUTHOR]

The article discusses the first recorded live-stranding of an Antarctic Minke Whale (AMW) in the Caribbean Sea, providing details on the identification process and morphological characteristics.Topics include the migration patterns of AMWs, diagnostic characteristics for identification, and potential causes for their presence in non-native regions.

Baleen whales are ecosystem sentinels of microplastic pollution. Research indicates that they likely ingest millions of anthropogenic microparticles per day when feeding. Their immense prey consumption and filter-feeding behavior put them at risk. However, the role of baleen, the oral filtering structure of mysticete whales, in this process has not been adequately addressed. Using actual baleen tissue from four whale species (fin, humpback, minke, and North Atlantic right) in flow tank experiments, we tested the capture rate of plastics of varying size, shape, and polymer type, as well as chemical residues leached by degraded plastics, all of which accumulated in the baleen filter. Expanded polystyrene foam was the most readily captured type of plastic, followed by fragments, fibers, nurdles, and spherical microbeads. Nurdle and microbead pellets were captured most readily by right whale baleen, and fragments were captured by humpback baleen. Although not all differences between polymer types were statistically significant, buoyant polymers were most often trapped by baleen. Plastics were captured by baleen sections from all regions of a full baleen rack, but were more readily captured by baleen from dorsal and posterior regions. Baleen–plastic interactions underlie various risks to whales, including filter clogging and damage, which may impede feeding. We posit that plastics pose a higher risk to some whale species due to a combination of factors, including filter porosity, diet, habitat and geographic distribution, and foraging ecology and behavior. Certain whale species in specific marine regions are of the greatest concern due to plastic abundance. It is not feasible to remove all plastic from the sea; most of what is there will continue to break into ever-smaller pieces. We suggest that higher priorities be accorded to lessening humans' dependence on plastics, restricting entry points of plastics into the ocean, and developing biodegradable alternatives. [ABSTRACT FROM AUTHOR]

Socially transmitted behavioural patterns (i.e. cultural traditions) have been observed in many whale species from large baleen whales to small dolphins. However, no cultural traditions have been described so far in beaked whales, an elusive and poorly studied group of toothed whales. In this study we report a local population of Baird's beaked whales, Berardius bairdii , in the Commander Islands regularly using a shallow area with depths of less than 300 m which is uncharacteristic for this species. We analysed the distribution of this behaviour and mtDNA haplotypes among individual whales to explore whether it represents a cultural tradition and whether it is transmitted vertically within separate maternal lineages or horizontally among nonrelated whales. We found that the whales that frequently visited the study area, and therefore were familiar with the underwater landscape, often used the shallow areas of the shelf slope, while transient whales, unfamiliar with the local conditions, mostly adhered to the depth range typical of their species. Only those transient whales that maintained social bonds with residents were sometimes observed in shallow areas. Order-of-acquisition diffusion analysis showed that social transmission of knowledge about the shallow habitat was significantly more likely than individual asocial learning. Two mtDNA haplotypes were shared between whales that used the shallow areas and those that did not, suggesting that these categories did not represent separate maternal lineages. We conclude that knowledge of the shallow areas is transmitted horizontally through social learning, and therefore this is an example of a local cultural tradition. • We report on the first possible cultural tradition in beaked whales. • Some Baird's beaked whales used a shallow area, which is atypical for this species. • Resident whales familiar with the local conditions often used the shallow area. • Only those transients that had social bonds with residents occurred in the shallows. • The knowledge of the shallow area is transmitted through social learning. [ABSTRACT FROM AUTHOR]

Many baleen whales are renowned for their acoustic communication. Under pristine conditions, this communication can plausibly occur across hundreds of kilometres. Frequent vocalisations may allow a dispersed migrating group to maintain contact, and therefore benefit from improved navigation via the "wisdom of the crowd". Human activities have considerably inflated ocean noise levels. Here we develop a data-driven mathematical model to investigate how ambient noise levels may inhibit whale migration. Mathematical models allow us to simultaneously simulate collective whale migration behaviour, auditory cue detection, and noise propagation. Rising ambient noise levels are hypothesised to influence navigation through three mechanisms: (i) diminished communication space; (ii) reduced ability to hear external sound cues and; (iii) triggering noise avoidance behaviour. Comparing pristine and current soundscapes, we observe navigation impairment that ranges from mild (increased journey time) to extreme (failed navigation). Notably, the three mechanisms induce qualitatively different impacts on migration behaviour. We demonstrate the model's potential predictive power, exploring the extent to which migration may be altered under future shipping and construction scenarios. [ABSTRACT FROM AUTHOR]

Off Northern Chile, baleen whales use the area around Isla Chañaral as a feeding ground where they forage on euphausiids. Isla Chañaral is part of the highly productive Humboldt Archipelago (~ 28°S-29°S) within the Humboldt Current System (HCS). In this study, we seek to understand the submesoscale spatial distribution of fin and blue whales and their prey around Isla Chañaral using systematic and opportunistic visual sighting data of whales and systematic acoustic backscatter data of zooplankton from an Acoustic Zooplankton and Fish Profiler (AZFP); and to examine the oceanographic dynamics of the wider Humboldt Archipelago area with remote-sensing oceanographic data. We completed a total of 512.6 km of survey effort over 20 days in 2018 and 318.3 km over 16 days in 2019 collecting systematic whale sighting and backscatter data. A total of 42 fin whales, 0 blue whales and 66 unidenti fied whales were sighted in 2018, and 7 fin whales, 3 blue whales and 12 unidentified whales were sighted in 2019. Observed spatial distribution of backscatter and whales was strongly associated with a bathymetric feature, i.e., the submarine canyon that curves around Isla Chañaral. Generalized Additive Models showed that fin whale presence was associated with high levels of backscatter and shallow depths similar to those of the canyon. We found that long-term average geostrophic currents form a recirculation system between 28°S and 31°S that can transport nutrient-rich upwelled surface waters back towards the Humboldt Archipelago and contribute to high biological productivity in this area. However, in summer 2019 geostrophic flow occurred away from the coast and a warm low-productivity spring explained low backscatter and whale sightings around Isla Chanaral. The unique oceanographic features of Isla Chanaral and the Humboldt Archipelago that contribute to high concentrations of Endangered baleen whales and their prey justify the extension of the Isla Chanaral Marine Reserve to include the canyon between the mainland and the island, and the implementation of a Multiple Use Marine Protected Area for the entire Humboldt Archipelago area that explicitly protects this critical feature. [ABSTRACT FROM AUTHOR]

Ocean bottom seismometer networks can record opportunistic data sets of 20-Hz fin whale calls. Because networks are often too sparse for multi-station tracking, single-station methods are needed to estimate call density. We investigated a method to range to singing fin whales at full ocean depths using the spacing of water column multiples. Calls were detected by cross-correlating a spectrogram with a template call. To enhance multipath signals, we considered 20-min windows and either summed the spectrograms of all calls aligned on the strongest detection before measuring the multipath spacing or measured the spacing directly from the autocorrelation of the cross correlation time series. We evaluated the methods at five sites with contrasting seafloor and subsurface properties, bathymetric relief, and water depths of 4000–6000 m, using fin whale songs at four sites and a sei whale song at the fifth. The autocorrelation method works best, and ranges can be obtained to >15 km. Ranging at sedimented sites requires careful accounting for subsurface reflections. Ranges have considerable uncertainty in regions of bathymetric relief. The method requires that the time between calls is different from that of the multipaths and does not work reliably when more than one whale is singing nearby. [ABSTRACT FROM AUTHOR]