Baleen Whales Research Articles

A Young Eden’s Whale (Balaenoptera edeni edeni) Wandering in a Busy International Container Port

Eden’s whale (Balaenoptera edeni edeni) is one of the least-understood baleen whales, with a global distribution that is almost completely unknown; only a few basic population studies of this species have been reported thus far. On 29 June 2021, a single Eden’s whale was sighted in Dapeng Bay, Shenzhen, a busy international container port. This sighting was the first record of a live Eden’s whale in the area, and it attracted immediate widespread attention. Our research team monitored the whale, nicknamed “Xiaobu” by Shenzhen citizens, until its disappearance. There were 48 sightings of the whale over a period of 50 days during vessel-based surveys from 2 July to 29 August 2021. Xiaobu was mainly sighted in coastal areas with a depth of 8.70 to 16.30 m; it remained 1 km offshore. The whale moved in a small minimum convex polygon range of 44.67 km2 and kernel density estimation range of 87.96 km2. From 2 to 27 July 2021, the whale was sighted near the Liquefied Natural Gas Pier in the eastern part of Dapeng Bay; it moved toward the Yantian International Container Terminal in the western part of Dapeng Bay between 28 July and 25 August, after which it was not sighted again. Its shift from east to west may have been influenced by food distribution and/or a gradual increase in familiarity with the local environment. Aerial vertical photogrammetry estimated a short body length of 7.49 m, indicating a young whale. Based on stranding records from the Chinese coastal area, the Eden’s whale population in Beibu Gulf presumably migrates northward to the East China Sea (approximately 2,000 km northeast) in April, and then returns in December. Xiaobu may have become separated from the Eden’s whale group when whales reached Shenzhen during the northward migration.

Acoustic behavior of gray whales tagged with biologging devices on foraging grounds

Understanding the function of baleen whale acoustic signals requires the investigation of calling behaviors relative to location, timing, and behavioral state. Previous studies of gray whale (Eschrichtius robustus) vocal behavior have principally used passive recorders and been conducted primarily on breeding grounds and along migratory routes, and not areas associated with foraging. We conducted an analysis of accelerometer and acoustic data collected during 12 deployments of animal-borne tags in 2016, 2019, and 2021 on gray whales that return annually to northern Puget Sound, Washington. We identified 141 calls from gray whales in approximately 128 hours of accelerometer and/or acoustic data collected from tag deployments. The most prominent were pulsive ‘rumble-like’ calls, upsweeping tones, and moans. Using the tag’s accelerometer to identify calls produced by tagged animals enabled us to explore the behavioral context behind call production, revealing that vocalizations were made primarily at slow speeds (mean 1.03 ± 0.26 m/s-1), shallow depths (mean 7.63 ± 4.99 m), and temporally proximate to surface behavior (mean 43.3 ± 39.66 sec) most similar to non-foraging associated depth (mean 5.78 ± 1.46 m and speed (mean 1.46 ± 1.11 m/s-1) profiles. Vocalizations originating from the tagged animal occurred closer to the conclusion of a foraging event (mean 87.7 ± 119.32 min) than the beginning, with only 7% of all calls occurring during periods of feeding. This study demonstrates that gray whales remain vocal on foraging grounds and that call-associated accelerometry signals can be a valuable tool in identifying individual callers in animal-borne acoustic data.

Assessment of a non-invasive approach to pregnancy diagnosis in gray whales through drone-based photogrammetry and faecal hormone analysis.

Knowledge of baleen whales' reproductive physiology is limited and requires long-term individual-based studies and innovative tools. We used 6 years of individual-level data on the Pacific Coast Feeding Group gray whales to evaluate the utility of faecal progesterone immunoassays and drone-based photogrammetry for pregnancy diagnosis. We explored the variability in faecal progesterone metabolites and body morphology relative to observed reproductive status and estimated the pregnancy probability for mature females of unknown reproductive status using normal mixture models. Individual females had higher faecal progesterone concentrations when pregnant than when presumed non-pregnant. Yet, at the population level, high overlap and variability in progesterone metabolite concentrations occurred between pregnant and non-pregnant groups, limiting this metric for accurate pregnancy diagnosis in gray whales. Alternatively, body width at 50% of the total body length (W50) correctly discriminated pregnant from non-pregnant females at individual and population levels, with high accuracy. Application of the model using W50 metric to mature females of unknown pregnancy status identified eight additional pregnancies with high confidence. Our findings highlight the utility of drone-based photogrammetry to non-invasively diagnose pregnancy in this group of gray whales, and the potential for improved data on reproductive rates for population management of baleen whales generally.

Zoop to poop: assessment of microparticle loads in gray whale zooplankton prey and fecal matter reveal high daily consumption rates

The ocean continues to be a sink for microparticle (MP) pollution, which includes microplastics and other anthropogenic debris. While documentation of MP in marine systems is now common, we lack information on rates of MP ingestion by baleen whales and their prey. We collected and assessed MP loads in zooplankton prey and fecal samples of gray whales (Eschrichtius robustus) feeding in coastal Oregon, USA and produced the first estimates of baleen whale MP consumption rates from empirical data of zooplankton MP loads (i.e., not modeled). All zooplankton species examined were documented gray whale prey items (Atylus tridens, Holmesimysis sculpta, Neomysis rayii) and contained an average of 4 MP per gram of tissue, mostly of the microfiber morphotype. We extrapolated MP loads in zooplankton prey to estimate the daily MP consumption rates of pregnant and lactating gray whales, which ranged between 6.5 and 21 million MP/day. However, these estimates do not account for MP ingested from ambient water or benthic sediments, which may be high for gray whales given their benthic foraging strategy. We also assessed MP loads in fecal samples from gray whales feeding in the same spatio-temporal area and detected MP in all samples examined, which included microfibers and significantly larger morphotypes than in the zooplankton. We theorize that gray whales ingest MP via both indirect trophic transfer from their zooplankton prey and directly through indiscriminate consumption of ambient MPs when foraging benthically where they consume larger MP morphotypes that have sunk and accumulated on the seafloor. Hence, our estimated daily MP consumption rates for gray whales are likely conservative because they are only based on indirect MP ingestion via prey. Our results improve the understanding of MP loads in marine ecosystems and highlight the need to assess the health impacts of MP consumption on zooplankton and baleen whales, particularly due to the predominance of microfibers in samples, which may be more toxic and difficult to excrete than other MP types. Furthermore, the high estimated rates of MP consumption by gray whales highlights the need to assess health consequences to individuals and subsequent scaled-up effects on population vital rates.

Do whales really increase the oceanic removal of atmospheric carbon?

Whales have been titled climate savers in the media with their recovery welcomed as a potential carbon solution. However, only a few studies were performed to date providing data or model outputs to support the hypothesis. Following an outline of the primary mechanisms by which baleen whales remove carbon from the atmosphere for eventual sequestration at regional and global scales, we conclude that the amount of carbon whales are potentially sequestering might be too little to meaningfully alter the course of climate change. This is in contrast to media perpetuating whales as climate engineers. Creating false hope in the ability of charismatic species to be climate engineers may act to further delay the urgent behavioral change needed to avert catastrophic climate change impacts, which can in turn have indirect consequences for the recovery of whale populations. Nevertheless, whales are important components of marine ecosystems, and any further investigation on existing gaps in their ecology will contribute to clarifying their contribution to the ocean carbon cycle, a major driver of the world’s climate. While whales are vital to the healthy functioning of marine ecosystems, overstating their ability to prevent or counterbalance anthropogenically induced changes in global carbon budget may unintentionally redirect attention from known, well-established methods of reducing greenhouse gases. Large scale protection of marine environments including the habitats of whales will build resilience and assist with natural carbon capture.

Allometric Growth of the Enigmatic Deep-Sea Megamouth Shark Megachasma pelagios Taylor, Compagno, and Struhsaker, 1983 (Lamniformes, Megachasmidae)

Megamouth sharks Megachasma pelagios Taylor, Compagno, and Struhsaker, 1983, are a large-bodied, planktivorous, deep-sea species with peculiar morphology. Since their initial description in the late 20th century, many individuals of different sizes have been reported, but few studies examined ontogenetic changes in body shapes. Here, we assess the growth changes in their heads and fins based on length measurements from nine different-sized individuals (177–544 cm in total length). Bivariate analyses showed that the head becomes larger relative to body length with increasing body size (i.e., positive allometry), whereas the relative size of the caudal fin remains constant (i.e., isometric growth). This trend differs from basking sharks and apparently resembles whale sharks and some baleen whales, although they are all large-bodied filter feeders. Given that relative mouth size is linked to feeding modes, our results suggest that megamouth sharks have different feeding modes from ram-feeding basking sharks and may have some similarity with suction-feeding whale sharks and engulfment-feeding baleen whales.

Kinematics and energetics of foraging behavior in Rice’s whales of the Gulf of Mexico

Rorqual foraging behavior varies with species, prey type and foraging conditions, and can be a determining factor for their fitness. Little is known about the foraging ecology of Rice’s whales (Balaenoptera ricei), an endangered species with a population of fewer than 100 individuals. Suction cup tags were attached to two Rice’s whales to collect information on their diving kinematics and foraging behavior. The tagged whales primarily exhibited lunge-feeding near the sea bottom and to a lesser extent in the water-column and at the sea surface. During 6–10 min foraging dives, the whales typically circled their prey before executing one or two feeding lunges. Longer duration dives and dives with more feeding-lunges were followed by an increase in their breathing rate. The median lunge rate of one lunge per dive of both animals was much lower than expected based on comparative research on other lunge-feeding baleen whales, and may be associated with foraging on fish instead of krill or may be an indication of different foraging conditions. Both animals spent extended periods of the night near the sea surface, increasing the risk for ship strike. Furthermore, their circling before lunging may increase the risk for entanglement in bottom-longline fishing gear. Overall, these data show that Rice’s whale foraging behavior differs from other lunge feeding rorqual species and may be a significant factor in shaping our understanding of their foraging ecology. Efforts to mitigate threats to Rice’s whales will benefit from improved understanding of patterns in their habitat use and fine-scale ecology.

Testing heterochrony: Connecting skull shape ontogeny and evolution of feeding adaptations in baleen whales.

Ontogeny plays a key role in the evolution of organisms, as changes during the complex processes of development can allow for new traits to arise. Identifying changes in ontogenetic allometry-the relationship between skull shape and size during growth-can reveal the processes underlying major evolutionary transformations. Baleen whales (Mysticeti, Cetacea) underwent major morphological changes in transitioning from their ancestral raptorial feeding mode to the three specialized filter-feeding modes observed in extant taxa. Heterochronic processes have been implicated in the evolution of these feeding modes, and their associated specialized cranial morphologies, but their role has never been tested with quantitative data. Here, we quantified skull shapes ontogeny and reconstructed ancestral allometric trajectories using 3D geometric morphometrics and phylogenetic comparative methods on sample representing modern mysticetes diversity. Our results demonstrate that Mysticeti, while having a common developmental trajectory, present distinct cranial shapes from early in their ontogeny corresponding to their different feeding ecologies. Size is the main driver of shape disparity across mysticetes. Disparate heterochronic processes are evident in the evolution of the group: skim feeders present accelerated growth relative to the ancestral nodes, while Balaenopteridae have overall slower growth, or pedomorphosis. Gray whales are the only taxon with a relatively faster rate of growth in this group, which might be connected to its unique benthic feeding strategy. Reconstructed ancestral allometries and related skull shapes indicate that extinct taxa used less specialized filter-feeding modes, a finding broadly in line with the available fossil evidence.

Distribution, hosts and long-term decline in abundance of the Patagonian lamprey inferred from diet assessment of albatrosses

Knowledge of lampreys during their marine phase is limited, and for the southern hemisphere species was gleaned from their predators (albatrosses) in the 1970s. Taking advantage of new methodologies and long-term data on predator diet and distributions, we infer diverse aspects of lamprey distribution and ecology. DNA analyses indicated that albatrosses at South Georgia prey on Patagonian lamprey Geotria macrostoma, originating from Argentina. Their core pelagic distribution when free swimming appears to be the Antarctic Polar Frontal zone (APFZ), and not South Georgia waters as assumed previously. If so, the APFZ would be the first known hotspot in abundance of an anadromous lamprey in oceanic waters. We could not identify a teleost fish that would be a likely host. Instead, we infer that the lamprey may prey on baleen whales, based on comparison of stable isotope ratios in lamprey with candidate host species, timing of appearance in albatross diets coincident with whale migrations, and circumstantial evidence (unexplained scarring recorded during the whaling era). We suggest that the lamprey do not tolerate cold Antarctic waters, and detach from southerly-migrating whales at the thermal boundary of the APFZ, where they become accessible to albatrosses in surface waters. Given strong evidence that relative importance of prey in seabird diets reflects availability in foraging areas, the steep decrease in the annual consumption of lamprey by albatrosses at South Georgia from > 550 tonnes in 1975–1976 and 1986, to very low levels in most years since 2012, is likely to indicate a major population decrease. Despite our unconventional means of assessing the population trend, there is a compelling case for listing of Patagonian lamprey at least as Near threatened by the International Union for the Conservation of Nature, and an urgent need to better understand anthropogenic threats in Argentina.

Potential impact of offshore human activities on gray whales (Eschrichtius robustus)

Gray whale (Eschrichtius robustus) reactions to offshore human activities have been relatively well studied compared to those of other mysticetes. Studies of short-term behavioural responses to underwater noise associated with aircraft, ships and seismic explorations indicate a 0.5 probability that whales will respond to continuous broadband noise when sound levels exceed ca 120dB2 and to intermittent noise when levels exceed ca 170dB, usually by changing their swimming course to avoid the source. Gray whales were ‘startled’ at the sudden onset of noise during playback studies, but demonstrated a flexibility in swimming and calling behaviour that may allow them to circumvent increased noise levels. Whales may be ‘harassed’ by noise from large commercial vessels, especially in shipping lanes or near busy ports. Gray whales sometimes change course and alter their swimming speed and respiratory patterns when followed by whalewatching boats. Conversely, some whales swim toward small skiffs deployed from whalewatching boats in breeding lagoons, seemingly attracted by the noise of idling outboard engines. Reported gray whale reactions to aircraft are varied and seem related to ongoing whale behaviour and aircraft altitude. Whale response to research involving tagging and biopsy sampling appears to be short term. Gray whales were seen swimming through surface oil from the Exxon Valdez oil spill along the Alaskan coast and showed only partial avoidance to natural oil seeps off the California coast. Laboratory tests suggest that gray whale baleen, and possibly skin, may be resistant to damage by oil, but spilled oil or oil dispersant in a primary feeding area could negatively affect gray whales by contaminating benthic prey. Gray whales are sometimes injured or killed in collisions with vessels or entanglement in fishing gear. Concern about the cumulative long-term impact of offshore human activities is particularly acute in the Southern California Bight, where many activities are often concurrent.

An HMM-DNN-Based System for the Detection and Classification of Low-Frequency Acoustic Signals from Baleen Whales, Earthquakes, and Air Guns off Chile

Marine passive acoustic monitoring can be used to study biological, geophysical, and anthropogenic phenomena in the ocean. The wide range of characteristics from geophysical, biological, and anthropogenic sounds sources makes the simultaneous automatic detection and classification of these sounds a significant challenge. Here, we propose a single Hidden Markov Model-based system with a Deep Neural Network (HMM-DNN) for the detection and classification of low-frequency biological (baleen whales), geophysical (earthquakes), and anthropogenic (air guns) sounds. Acoustic data were obtained from the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization station off Juan Fernandez, Chile (station HA03) and annotated by an analyst (498 h of audio data containing 30,873 events from 19 different classes), and then divided into training (60%), testing (20%), and tuning (20%) subsets. Each audio frame was represented as an observation vector obtained through a filterbank-based spectral feature extraction procedure. The HMM-DNN training procedure was carried out discriminatively by setting HMM states as targets. A model with Gaussian Mixtures Models and HMM (HMM-GMM) was trained to obtain an initial set of HMM target states. Feature transformation based on Linear Discriminant Analysis and Maximum Likelihood Linear Transform was also incorporated. The HMM-DNN system displayed good capacity for correctly detecting and classifying events, with high event-level accuracy (84.46%), high weighted average sensitivity (84.46%), and high weighted average precision (89.54%). Event-level accuracy increased with higher event signal-to-noise ratios. Event-level metrics per class also showed that our HMM-DNN system generalized well for most classes but performances were best for classes that either had a high number of training exemplars (e.g., generally above 50) and/or were for classes of signals that had low variability in spectral features, duration, and energy levels. Fin whale and Antarctic blue whale song and air guns performed particularly well.

New specimens and species of the Oligocene toothed baleen whaleCoronodonfrom South Carolina and the origin of Neoceti

Baleen whales (Mysticeti) are gigantic filter-feeding cetaceans possessing the unique soft tissue structure baleen and lacking adult teeth; Oligocene fossils have revealed a wealth of early diverging tooth-bearing mysticetes highlighting the transition from archaeocete ancestors to early toothless baleen-bearing eomysticetid whales. The archaeocete-like, toothed mysticeteCoronodon havensteinifrom the lower Oligocene Ashley Formation of South Carolina possesses a number of peculiar aspects of feeding morphology suggesting dental filter-feeding in the earliest diverging mysticete lineage. New fossils ofCoronodonare described in detail, including (1) supplementary description of the holotype skull and skeleton ofCoronodon havensteini; (2) description of two new juvenile skulls ofC. havensteiniand a partial skull and postcranial skeleton of an adult; (3) description of the new speciesCoronodon planifronsn.sp.; and (4) description of the new speciesCoronodon newtonorum. New specimens ofCoronodon havensteiniinclude a partial adult skeleton preserving new elements for the species including incisors, numerous upper premolars and molars, lower m4, scapula, lumbar, and caudal vertebrae, and two juvenile skulls with tympanoperiotics and teeth. Fossils from the overlying unit, the Chandler Bridge Formation, represent two new species:Coronodon newtonorumn. sp. andCoronodon planifronsn. sp.Coronodon newtonorumpossesses a concave-up alveolar profile, a mandibular condyle elevated far above the toothrow, and a gracile periotic resembling those of juvenileC. havensteini.Coronodon planifronsn. sp. possesses a horizontal supraorbital process, successively smaller upper molars, massively inflated periotic, and longer intertemporal region.Coronodon planifronsn. sp. preserves one of the most complete vertebral columns among toothed mysticetes, indicating nine thoracic vertebrae, ten lumbar vertebrae, and at least 20 caudal vertebrae. The column exhibits a somewhat stabilized caudal peduncle with enlarged lumbocaudal vertebrae, and rectangular terminal caudals indicate the presence of tail flukes. Juvenile skulls reveal several ontogenetic trends inCoronodon havensteini, including the anterior migration of the orbitotemporal crest, anteroposterior elongation of the intertemporal region, inflation of the body of the periotic, enlargement of the tympanic bulla, and continued postnatal emergence of the premolars and molars from their alveoli. Disarticulated skulls suggest a degree of rostral kinesis in this genus. Phylogenetic analysis of the largest assembled supermatrix of Mysticeti (n=138 OTUs; four archaeocetes, 10 odontocetes, 124 mysticetes; 391 morphological and 27,225 molecular characters) confirms placement ofCoronodonas the earliest diverging lineage of Mysticeti under equally weighted analyses whereas implied weighting placesCoronodonand similar taxa outside Neoceti, prompting a review of character transformations at the base of Neoceti.

The genome of the pygmy right whale illuminates the evolution of rorquals

BackgroundBaleen whales are a clade of gigantic and highly specialized marine mammals. Their genomes have been used to investigate their complex evolutionary history and to decipher the molecular mechanisms that allowed them to reach these dimensions. However, many unanswered questions remain, especially about the early radiation of rorquals and how cancer resistance interplays with their huge number of cells. The pygmy right whale is the smallest and most elusive among the baleen whales. It reaches only a fraction of the body length compared to its relatives and it is the only living member of an otherwise extinct family. This placement makes the pygmy right whale genome an interesting target to update the complex phylogenetic past of baleen whales, because it splits up an otherwise long branch that leads to the radiation of rorquals. Apart from that, genomic data of this species might help to investigate cancer resistance in large whales, since these mechanisms are not as important for the pygmy right whale as in other giant rorquals and right whales.ResultsHere, we present a first de novo genome of the species and test its potential in phylogenomics and cancer research. To do so, we constructed a multi-species coalescent tree from fragments of a whole-genome alignment and quantified the amount of introgression in the early evolution of rorquals. Furthermore, a genome-wide comparison of selection rates between large and small-bodied baleen whales revealed a small set of conserved candidate genes with potential connections to cancer resistance.ConclusionsOur results suggest that the evolution of rorquals is best described as a hard polytomy with a rapid radiation and high levels of introgression. The lack of shared positive selected genes between different large-bodied whale species supports a previously proposed convergent evolution of gigantism and hence cancer resistance in baleen whales.

The effect of age and sex selective harvest patterns for baleen whales

The taking of calves and females accompanied by calves is prohibited under the original and current forms of the Schedule of the International Whaling Commission. Proposed regulations under the Revised Management Scheme would reduce catch limits according to the proportion of females in the landings when females make up more than one-half of the landings. The implications of regulations on age, sex and reproductive status were explored by examining the relative impacts of baleen whale harvests with different age, sex and female reproductive status selectivity patterns using a matrix population model. The effects of 11 harvest patterns with varying selectivity for females and calves were measured by computing the fraction of the population that would have to be killed to reduce the growth rate of the population model to zero and the corresponding fraction of the population that would be landed (harvest fraction). The harvest impact per whale landed was measured for each selectivity pattern by expressing the harvest fraction as a percentage of the value of that fraction for a harvest random across age, sex and reproductive status. The harvest impacts per whale landed of the 11 patterns ranged from 64% greater to 29% lower than a random harvest. The patterns with the lowest harvest impact per whale landed were the pattern consistent with the IWC Schedule of prohibiting harvest of calves and females accompanied by calves, and the pattern of harvesting only calves. The harvest selectivity patterns which increased the vulnerability of females had the greatest impact. Relative to the IWC’s Revised Management Procedure, this increased female vulnerability was roughly compensated for by the decrease in catch limits as the proportion of females in the catches increased.

Osteological correlates of evolutionary transitions in cetacean feeding and related oropharyngeal functions

Teeth are often the first structures that anatomists and paleontologists examine to understand the ecology and morphology of feeding, both because teeth are highly specialized structures that provide precise information, and because they are among the best and most commonly preserved fossils. Unfortunately, many fragmentary fossil and recent specimens lack teeth, and some come from edentulous individuals and taxa, as in mysticete (baleen) whales. In our broad comparative review, we survey non-dental osteological features that, due to size, shape, arrangement, and surface features reflecting muscle attachments, provide useful clues to general or specific aspects of prey capture, intraoral transport, processing, or swallowing. We focus on hyoid, palatal, and pterygoid bones, mandibular symphyses and processes such as the coronoid, and the temporal fossa and zygomatic arch, as well as adjacent cranial bones relating to oral and pharyngeal anatomy. These bones relate to muscles of five general locations especially indicative of feeding: mandibular, hyoid, tongue, pharyngeal, and facial regions. Together these bones and muscles affect feeding and related activities including suckling and breathing. We discuss osteological correlates that provide special relevance to key transitions in cetacean evolutionary history, such as the shift from predominantly terrestrial to aquatic feeding, the shift from typical mammalian mastication to swallowing prey entirely or nearly whole, and the separation of respiratory and digestive passages. We also point to examples of modern specialists in these anatomical optima for different modes of prey capture, intraoral transport, processing, and swallowing. Although we focus on cetaceans, our approach is broadly relevant to all vertebrates, notably other marine tetrapods.

The contribution of penguin guano to the Southern Ocean iron pool

Iron plays a crucial role in the high-nutrient, low-chlorophyll Southern Ocean regions, promoting phytoplankton growth and enhancing atmospheric carbon sequestration. In this area, iron-rich Antarctic krill (Euphausia superba) and baleen whale species, which are among their main predators, play a large role in the recycling of iron. However, penguins have received limited attention despite their representing the largest seabird biomass in the southern polar region. Here, we use breeding site guano volumes estimated from drone images, deep learning-powered penguin census, and guano chemical composition to assess the iron export to the Antarctic waters from one of the most abundant penguin species, the Chinstrap penguin (Pygoscelis antarcticus). Our results show that these seabirds are a relevant contributor to the iron remobilization pool in the Southern Ocean. With an average guano concentration of 3 mg iron g−1, we estimate that the Chinstrap penguin population is recycling 521 tonnes iron yr−1, representing the current iron contribution half of the amount these penguins were able to recycle four decades ago, as they have declined by more than 50% since then.

Minke whales change their swimming behavior with respect to their calling behavior, nearby conspecifics, and the environment in the central North Pacific

Behavioral responses to sonar have been observed in a number of baleen whales, including minke whales (Balaenoptera acutorostrata). Previous studies used acoustic minke whale boing detections to localize and track individual whales on the U.S. Pacific Missile Range Facility (PMRF) in Kaua ‘i, Hawai‘i before, during, and after Navy training activities. These analyses showed significant changes in central North Pacific minke whale distribution and swimming behavior during Navy sonar events. For the purposes of contextualizing changes in animal movement relative to Navy sonar, we expanded on this research to examine the natural variation in minke whale movement when Navy sonar was not present. This study included 2,245 acoustically derived minke whale tracks spanning the years 2012–2017 over all months that minke whales were detected (October–May). Minke whale movement was examined relative to calling season, day of the year, hour of day, wind speed, calling state (nominal or rapid), and distance to the nearest calling conspecific. Hidden Markov models were used to identify two kinematic states (slower, less directional movement and faster, more directional movement). The findings indicate that minke whales were more likely to travel in a faster and more directional state when they were calling rapidly, when other vocalizing minke whales were nearby, during certain times of the day and calling seasons, and in windier conditions, but these changes in movement were less intense than the changes observed during exposure to Navy sonar, when swim speeds were the fastest. These results start to put behavioral responses to Navy sonar into an environmental context to understand the severity of responses relative to natural changes in behavior.

Overview of minke whale sightings surveys conducted on IWC/IDCR and SOWER Antarctic cruises from 1978/79 to 2000/01

The IWC Southern Hemisphere minke whale assessment cruises (IDCR and SOWER) have been conducted since 1978/79 in the Antarctic regions of all six IWC management Areas for baleen whales (covering all, or more recently, part, of one Area each season). During the 23-year history of the programme to 2000/01, a total search distance on primary effort of 70,340 n.miles has been achieved during 2,448 ship-days in the Antarctic. A total of 6,027 primary minke whale school sightings were recorded. Over the years, there have been two major and some minor modifications to the survey design as a result of the development of survey procedures. These developments represent the best possible compromise between statistical needs and logistics. This paper outlines the most significant modifications that have occurred to the research equipment, protocols and data collection. Some preliminary results are also included. From 1985/86, the beginning of the second circumpolar set of cruises, the programme (initially a combination of Discovery marking and sightings) became essentially a dedicated line-transect systematic sightings cruise only. Modification of the survey design from the third circumpolar set of cruises (from 1991/92), to cover the whole region south of 60°S in the Antarctic resulted in a change in emphasis of the latitudinal coverage, especially in Areas I, II, III and V; the implications of this are discussed. The paper also describes: guidelines for the identification of minke whales; methods used for assessment of duplicate status in passing mode with independent observer; the protocol used for conducting the estimated angle and distance experiment; and methods used for determining the southern boundary of the research area (ice-edge). The programme has also enabled collection of biopsy, photo-identification, oceanographic and acoustic samples, and can be adapted to research programmes in other parts of the world. It is concluded that the programme has developed and established standard sighting procedures and has also improved the precision of whale identification standards in the Southern Ocean.

First Stranding Event of a Common Minke Whale (Balaenoptera acutorostrata Lacépède, 1804) Reported in the Gulf of Thailand

On 5 September 2022, a dead baleen whale was found stranded at Laem Phak Bia, Phetchaburi, the Gulf of Thailand, Thailand but could not be identified because it was in an advanced stage of decomposition. It was first suspected to be Omura’s whale (Balaenoptera Omurai), as that is a common species in the Gulf of Thailand. However, the cranium morphology was different from B. omurai and more similar to the common minke whale (Balaenoptera acutorostrata) from the North Pacific Ocean, which has never been reported in Thai territorial waters. The mitochondrial DNA control region (D-loop) was then used to identify the species through the Basic Local Alignment Search Tool (BLAST) available at the National Center for Biotechnology Information (NCBI) GenBank, which resulted in a high percent identity, 96.49 to 98.84, with B. acutorostrata. A Bayesian phylogenetic tree was further used to confirm the species, which grouped with B. acutorostrata from the North Pacific Ocean. This study provides evidence of the first stranding event of B. acutorostrata in the Gulf of Thailand. It is new information that extends previous knowledge on the distribution of the common minke whale and raises the need for more active surveys of cetaceans in the South China Sea going forward.

A New Specimen of cf. Isanacetus laticephalus (Baleen Whale) from the Oi Formation, Ichishi Group (Late Early Miocene) in Japan

In the history of baleen whales, the early Miocene is one of not a well-known time. Many baleen whales from the Miocene are known as “cetotheres”. The “cetothere” Isanacetus laticephalus was a baleen whale from the early to middle Miocene that is only known from Japan. The holotype and paratype of I. laticephalus are well-preserved, and the age of the species I. laticephalus makes it one of the earlier basal plicogulans; however, its phylogenetic position is unclear. Here, a new cranium including the periotic from an early Miocene deposit (about 18.5 to 17.0 Ma) of the Oi Formation, Ichishi Group in Mie, Japan is reported as cf. I. laticephalus. The specimen displays a combination of four periotic features: (i) a large lateral tuberosity; (ii) a rectangular pars cochlearis; (iii) a robust neck of the posterior process, and (iv) a cerebral aperture of the facial canal that is smaller than that of the dorsal vestibular area. This combination of features could be diagnostic for I. laticephalus, among basal plicogulans from the early and middle Miocene. Adding more referred specimens will expand the diagnoses of I. laticephalus, and firmly support phylogenetic trees with this species.