Odontocetes Research Articles

Parallel Spectral Tuning of a Cone Visual Pigment Provides Evidence for Ancient Deep-Sea Adaptations in Cetaceans.

Dichromatic color vision is mediated by two cone visual pigments in many eutherian mammals. After reentry into the sea, early cetaceans lost their violet-sensitive visual pigment (short wavelength-sensitive 1) independently in the baleen and toothed whale ancestors and thus obtained only monochromatic cone vision. Subsequently, losses of the middle/long wavelength-sensitive (M/LWS) pigment have also been reported in multiple whale lineages, leading to rhodopsin (RH1)-mediated rod monochromatic vision. To further elucidate the phenotypic evolution of whale visual pigments, we assessed the spectral tuning of both M/LWS and RH1 from representative cetacean taxa. Interestingly, although the coding sequences for M/LWS are intact in both the pygmy right whale and the Baird's beaked whale, no spectral sensitivity was detected in vitro. Pseudogenization of other cone vision-related genes is observed in the pygmy right whale, suggesting a loss of cone-mediated vision. After ancestral sequence reconstructions, ancient M/LWS pigments from cetacean ancestors were resurrected and functionally measured. Spectral tuning of M/LWS from the baleen whale ancestor shows that it is green sensitive, with a 40-nm shift in sensitivity to a shorter wavelength. For the ancestor of sperm whales, although no spectral sensitivity could be recorded for its M/LWS pigment, a substantial sensitivity shift (20 to 30 nm) to a shorter wavelength may have also occurred before its functional inactivation. The parallel phenotypic evolution of M/LWS to shorter wavelength sensitivity might be visual adaptations in whales allowing more frequent deep-sea activities, although additional ecological differentiations may have led to their subsequent losses.

Feeding mode drives mandibular shape in extant Delphinidae

AbstractDelphinidae is the most diverse family within the toothed whale clade, displaying two biosonar modes, different feeding strategies, and diving and habitat adaptations. This work examines the delphinid mandible to determine the association between shape, size and ecological variables in extant species. Geometric morphometric analysis on 95 mandibles belonging to 30 (out of 38) extant species, representatives of all 17 extant genera, was performed in occlusal (or dorsal) and lateral (or labial) view. The results reveal that feeding mode and climate primarily drive mandibular shape in extant species. Biosonar mode is an evolutionary driver in mandibular shape in occlusal view, while diet and maximum prey size play a significant role in size only in both views. By contrast, Diving Ecology, Superficial Temperature and Rostral index do not play a significant role in driving delphinid mandibular shape and size.

Whale Collections and Exhibitions at the Natural History Museum of the University of Pisa (Italy)

The Natural History Museum of the University of Pisa hosts the most important osteological collection of extant cetaceans in Italy as well as one of the most relevant all over Europe. Furthermore, it also preserves a significant palaeontological collection that includes several holotypes and otherwise unique specimens of Archaeoceti (archaic cetaceans), Mysticeti (baleen whales) and Odontoceti (toothed whales). Here, we provide a historical overview of these collections and the corresponding displays, with special attention paid to the origin, development and design of the ‘Archaeocete Hall’ and ‘Cetacean Gallery’. These comprise what may be the largest exhibition worldwide among those dedicated exclusively to cetaceans—one that includes 28 complete skeletons and one skull belonging to 27 extant species as well as fossils of nine extinct species. Our review also reveals that the museum exhibitions feature the oldest known specimen of Mesoplodon bowdoini and the type specimen of Ziphius savi, the latter being a validly described species that is currently regarded as a junior synonym of Ziphius cavirostris. Also significant is the display of several holotype specimens of fossil species such as the protocetid archaeocete Aegyptocetus tarfa, the balaenid baleen whales Balaena montalionis and Balaenula astensis, and the monodontid Casatia thermophila. The Archaeocete Hall and Cetacean Gallery are highly appreciated by visitors as well as perused by the museum’s educational team. The online archiving of 3D models of many of the MSNUP specimens on the open-access digital repository Sketchfab and their subsequent dissemination through the Wikimedia platforms has led to the creation of a major osteological resource—one that is broadly accessible to internet users worldwide.

Exploring the ecosystem structure of Zanzibar archipelago, trophic flows and fisheries interaction by using a mass balance modelling approach

The marine ecosystem in the Zanzibar archipelago has great economic and ecological importance due to high fisheries productivity. Yet, limited information is available on its status and possible impacts of fishing on it. Ecological models have been recognized as powerful tools for assessing the structure and function of ecosystems and forecasting the impacts of human activities on marine ecosystems. However, the use of ecological models in understanding ecosystems in the Western Indian Ocean region is inadequate. This study constructed a model to examine the ecosystem functioning, trophic flows, and fisheries interactions of the marine region affected by fishing gears in the Zanzibar archipelago using Ecopath with Ecosim software. The model includes 34 functional groups and 10 most common fishing gears, the input parameters were gathered from published reports. The ecosystem indicators showed that the Zanzibar ecosystem is in the early developmental stage contributed by strong fishing pressure that reduces the stability and maturity of the ecosystem. The total catch estimated at 5.538 t km−2year−1 showed a sign of the high exploitation rate of fisheries resources. The catch is dominated by higher trophic level fish as reflected in the mean trophic level of the fishery (3.2). The keystoneness analysis identified pelagic cephalopods, sharks and rays, turtles, tuna and tuna like species and toothed whales for their importance in the Zanzibar marine ecosystem. Fishing pressure on the ecosystem of Zanzibar is high, hence for better management, the focus should be for coral reef and pelagic species that are highly targeted by number of gears while protecting keystone species as important groups of the ecosystem. Fisheries harvest data collection system should be improved to collect information at species level and focus on all target species, including invertebrates.

Conservation and selective pressures shaping baleen whale olfactory receptor genes supports their use of olfaction in the marine environment.

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.

Proximity labelling of pro-interleukin-1α reveals evolutionary conserved nuclear interactions.

Interleukin-1α is a suggested dual-function cytokine that diverged from interleukin-1β in mammals potentially by acquiring additional biological roles that relate to highly conserved regions in the pro-domain of interleukin-1α, including a nuclear localisation sequence and histone acetyltransferase-binding domains. Why evolution modified pro-interleukin-1α's subcellular location and protein interactome, and how this shaped interleukin-1α's intracellular role, is unknown. Here we show that TurboID proximity labelling with pro-interleukin-1α suggests a nuclear role for pro-interleukin-1α that involves interaction with histone acetyltransferases, including EP300. We also identify and validate inactivating mutations in the pro-interleukin-1α nuclear localisation sequence of multiple mammalian species, including toothed whales, castorimorpha and marsupials. However, histone acetyltransferase-binding domains are conserved in those species that have lost pro-interleukin-1α nuclear localisation. Together, these data suggest that histone acetyltransferase binding and nuclear localisation occurred together, and that while some species lost the nuclear localisation sequence in their pro-interleukin-1α, histone acetyltransferase binding ability was maintained. The nuclear localisation sequence was lost from several distinct species at different evolutionary times, suggesting convergent evolution, and that the loss of the nuclear localisation sequence confers some important biological outcome.

Evolution of ion channels in cetaceans: a natural experiment in the tree of life

Cetaceans represent a natural experiment within the tree of life in which a lineage changed from terrestrial to aquatic habitats. This shift involved phenotypic modifications, representing an opportunity to explore the genetic bases of phenotypic diversity. Among the different molecular systems that maintain cellular homeostasis, ion channels are crucial for the proper physiological functioning of all living species. This study aims to explore the evolution of ion channels during the evolutionary history of cetaceans. To do so, we created a bioinformatic pipeline to annotate the repertoire of ion channels in the genome of the species included in our sampling. Our main results show that cetaceans have, on average, fewer protein-coding genes and a higher percentage of annotated ion channels than non-cetacean mammals. Signals of positive selection were detected in ion channels related to the heart, locomotion, visual and neurological phenotypes. Interestingly, we predict that the NaV1.5 ion channel of most toothed whales (odontocetes) is sensitive to tetrodotoxin, similar to NaV1.7, given the presence of tyrosine instead of cysteine, in a specific position of the ion channel. Finally, the gene turnover rate of the cetacean crown group is more than three times faster than that of non-cetacean mammals.

Context-driven communication during deep-sea foraging in a social toothed whale.

Social deep-diving odontocetes face the challenge of balancing near-surface proximity to oxygen and group members with foraging in the deep sea. Individuals rely on conspecifics for critical life functions, such as predator defence, but disperse during foraging to feed individually. To understand the role of social acoustic mediation during foraging in deep-diving toothed whales, we investigated the context of social burst-pulse call production in Risso's dolphin (Grampus griseus) using biologgers. Dolphins produced context-specific burst pulses predominantly during daytime foraging, preceding or following foraging dives and in the early descent of daytime deep dives. Individuals applied differential short and long burst-pulse calls intended for either near-surface receivers (horizontal transmission) or deep-foraging receivers (vertical transmission). Our results show that deep-diving toothed whales are reliant on acoustic communication during certain foraging contexts, to relay information including foraging conditions or an individual's location. Moreover, they accentuate the importance of maintaining acoustic contact with conspecifics, specifically when dispersed during deeper foraging. It also signifies that our oceanic top predators may be specifically vulnerable to the current strong increase in anthropogenic noise. Potential masking of the signals from group members communicating at a distance could undermine their social cohesion, and hence their capacity to maintain vital life functions.

Abundance of humpback whales in the eastern Indian sector of the Southern Ocean in 2018/19 using opportunistic sighting survey data with a note on the occurrence of other cetaceans

Past commercial whaling depleted the humpback whale in the Southern Ocean; however, its population has recovered since hunting was terminated in 1966. Information on abundance is essential not only managing target animals but understanding the ecosystem because the species is one of the main consumers of Antarctic krill. Abundance of this species has not been reported in the eastern Indian sector (80–150°E) of the Southern Ocean since the mid-2000s. A multidisciplinary ecosystem survey focusing on Antarctic krill was conducted in the area by the Japanese research vessel Kaiyo-maru in 2018/19 austral summer. An opportunistic cetacean sighting survey (platform of opportunity (POP) survey) was conducted as part of the survey. Four baleen and five toothed whale species were sighted during the sighting survey. Humpback whales (113 schools/178 animals) were most frequently observed, followed by fin whales (15/36). Abundance of humpback whales was estimated as 22,395 individuals (CV = 0.270, 95 % confidence intervals: 13,310–37,663) based on the design-based line transect method. Krill consumption by humpback whales in this area was tentatively estimated as 1.336 million tons, corresponding to 30.9 % of krill biomass, although the amount varied greatly depending on the consumption rate’s assumption. The estimated abundance was comparable with previous estimates, however, there are some caveats in interpreting the results. As no approaching whale sightings were made during this POP survey, the proportion of sightings of unidentified large whales was high, possibly leading to an underestimation of the abundance. Dedicated sighting surveys are desirable to obtain more accurate and unbiased abundance estimates, especially for management purposes, although the results of this study could be used for ecological studies in combination with other data sets recoded by the multidisciplinary survey.

Estimation of chronological age of Risso’s dolphin (Grampus griseus) based on DNA methylation frequency

Age of cetaceans is an important data set for their conservation and management. Although the chronological age of a toothed whale has traditionally estimated from the number of annual tooth growth layer groups (GLGs), this method has potential difficulties such as errors due to the subjectivity of the age-readers and time-consuming sample processing, in addition to lethal tooth sampling in many cases. To overcome these difficulties through a non-lethal approach, considerable amount of efforts has been made in recent years to construct chronological age estimation models based on the correlation between chronological and biological age expressed as the frequency of DNA methylation at CpG (cytosine-phosphate-guanine) sites. The present study, by using next-generation sequencing on DNA extracted from the skin tissues of 30 individuals (15 males and 15 females), performed methylation analysis on multiple CpG sites in the three genes previously reported as age-linked in cetaceans (GRIA2, TET2, and CDKN2A) to construct an age estimation model for Risso’s dolphins. Key aspects of this study are: (1) the chronological ages of Risso’s dolphins of wild origins used in this study had been determined by the GLGs of teeth prior to this study, and (2) as Risso’s dolphins are said to have a lifespan of 30 years, samples were collected from individuals aged 1–29 years, covering from young to old ages. Among the 11 CpG sites in GRIA2, 6 CpG sites in TET2, and 7 CpG sites in CDKN2A analyzed, the CpG sites in GRIA2 showed a statistically significant correlation with age, whereas those in TET2 and CDKN2A did not show such a strong correlation. Using multiple regression analysis on the CpG sites in the three genes, the best fitted model was expressed as follows: y=-0.7548 + 5.6164x(GRIA2_CpG3)+2.6187x(TET2_CpG6)-1.5907x(CDKN2A_CpG3) (R²=0.7062, residual mean=2.98, standard deviation=2.3). With the mean error of 2.98 years between the estimated and known chronological ages, the accuracy of this model was found to be comparable to or higher than that of previously reported age estimation models for cetaceans. This study demonstrated for the future that the age of wild Risso’s dolphins can be estimated by using their skin samples collected with minimal invasiveness.

Cetaceans are the next frontier for vocal rhythm research

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.

Interactions between Cetaceans (suborder Odontoceti) and Artisanal Fishing in Brazil: an ethnoecological approach

Studies based on the relationship between humans and the natural environment have been proven to be important tools for understanding the influence, knowledge, and perceptions associated with the web of interactions between humans, species and ecosystems. Here, we highlight the interactions between cetaceans and artisanal fishing. Thus, this study aimed to: a) compile studies that consider artisanal fishing and its interactions with small cetaceans in Brazil; b) understand research trends over the years; c) analyse the distribution of studies by country region; d) perform authorship and citation analyses; e) classify the interactions between cetaceans and artisanal fishing recorded by authors and f) identify dolphin species registered in the study. To achieve this, we reviewed the current status of national publications related to the interactions of cetaceans (suborder Odontoceti) with artisanal fishing in Brazil, focusing on ethnoecological studies. Seven databases were used to survey the studies. To classify the interactions, we adopted the categorization proposed by Freitas-Netto and adapted by Di Beneditto. Based on the data analysis, we registered 12 types of interactions, seven of which were grouped according to the descriptions proposed by Di Beneditto and five new categories were described based on the results of this study. The studies reported the interaction of 43.2% (n=16) of the 37 odontocete species reported to occur in Brazil, with emphasis on the species Sotalia guianensis, Tursiops truncatus, Pontoporia blainvillei, Inia geoffrensis and Sotalia fluviatilis. From our research it was possible to observe that ethnoecological studies allow us to answer important questions about the occurrence of species and aspects of fishing. Furthermore, we reinforce the importance of developing studies which focus on the knowledge of the existing relationships between cetaceans and traditional fishing methods, since studies on this topic can generate data that contribute to the establishment of mitigation strategies and the management of species and ecosystems.

Meta-analysis of the Cetacea gut microbiome: Diversity, co-evolution, and interaction with the anthropogenic pathobiome

Despite their critical roles in marine ecosystems, only few studies have addressed the gut microbiome (GM) of cetaceans in a comprehensive way. Being long-living apex predators with a carnivorous diet but evolved from herbivorous ancestors, cetaceans are an ideal model for studying GM-host evolutionary drivers of symbiosis and represent a valuable proxy of overall marine ecosystem health. Here, we investigated the GM of eight different cetacean species, including both Odontocetes (toothed whales) and Mysticetes (baleen whales), by means of 16S rRNA-targeted amplicon sequencing. We collected faecal samples from free-ranging cetaceans circulating within the Pelagos Sanctuary (North-western Mediterranean Sea) and we also included publicly available cetacean gut microbiome sequences. Overall, we show a clear GM trajectory related to host phylogeny and taxonomy (i.e., phylosymbiosis), with remarkable GM variations which may reflect adaptations to different diets between baleen and toothed whales. While most samples were found to be infected by protozoan parasites of potential anthropic origin, we report that this phenomenon did not lead to severe GM dysbiosis. This study underlines the importance of both host phylogeny and diet in shaping the GM of cetaceans, highlighting the role of neutral processes as well as environmental factors in the establishment of this GM-host symbiosis. Furthermore, the presence of potentially human-derived protozoan parasites in faeces of free-ranging cetaceans emphasizes the importance of these animals as bioindicators of anthropic impact on marine ecosystems.

Isotopic niches reveal the trophic structure of the cetacean community in the oceanic waters around the Azores

IntroductionThe 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.MethodsHere we used stable isotope (δ13C and δ15N) 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 discussionδ13C and δ15N 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.

Reproductive Cessation and Post-Reproductive Lifespan in Honeybee Workers.

The post-reproductive lifespan is an evolutionary enigma because the cessation of reproduction in animals seems contrary to the maximization of Darwinian fitness. Several theories aim to explain the evolution of menopause, one of which suggests that females of a certain age receive more fitness benefits via indirect selection (kin selection) than they would directly from continuing reproduction. Post-reproductive lifespans are not very common in nature but have been described in humans, nonhuman primates, a few species of toothed whales, guppies, and in some insect societies consisting of clonal colony members, such as aphid and ant societies. Here, we provide evidence that menopause also exists in honeybee societies. Our study shows that workers with a short life expectancy (older and/or injured workers) invest fewer resources and less time in their own reproduction than workers with a long life expectancy (younger and/or uninjured workers), even if their colony is hopelessly queenless. These results are consistent with the kin selection explanation for the evolution of menopause and help us understand the net effects of relatedness and social cooperation in animals.

Accurate species classification of Arctic toothed whale echolocation clicks using one-third octave ratios.

Passive acoustic monitoring has been an effective tool to study cetaceans in remote regions of the Arctic. Here, we advance methods to acoustically identify the only two Arctic toothed whales, the beluga (Delphinapterus leucas) and narwhal (Monodon monoceros), using echolocation clicks. Long-term acoustic recordings collected from moorings in Northwest Greenland were analyzed. Beluga and narwhal echolocation signals were distinguishable using spectrograms where beluga clicks had most energy >30 kHz and narwhal clicks had a sharp lower frequency limit near 20 kHz. Changes in one-third octave levels (TOL) between two pairs of one-third octave bands were compared from over one million click spectra. Narwhal clicks had a steep increase between the 16 and 25 kHz TOL bands that was absent in beluga click spectra. Conversely, beluga clicks had a steep increase between the 25 and 40 kHz TOL bands that was absent in narwhal click spectra. Random Forest classification models built using the 16 to 25 kHz and 25 to 40 kHz TOL ratios accurately predicted the species identity of 100% of acoustic events. Our findings support the use of echolocation TOL ratios in future automated click classifiers for acoustic monitoring of Arctic toothed whales and potentially for other odontocete species.

Management and research efforts are failing dolphins, porpoises, and other toothed whales

Despite being subject to intensive research and public interest many populations of dolphins, porpoises, and other toothed whales (small cetaceans) continue to decline, and several species are on the verge of extinction. We examine small cetacean status, human activities driving extinction risk, and whether research efforts are addressing priority threats. We estimate that 22% of small cetaceans are threatened with extinction, with little signs of improvement in nearly thirty years. Fisheries and coastal habitat degradation are the main predictors of extinction risk. Contrary to popular belief, we show that the causal impact of small-scale fisheries on extinction risk is greater than from large-scale fisheries. Fisheries management strength had little influence on extinction risk, suggesting that the implementation of existing measures have been largely ineffective. Alarmingly, we find research efforts for priority threats to be vastly underrepresented and so a major shift in research focus is required. Small cetaceans are among the lower hanging fruits of marine conservation; continued failure to halt their decline bodes poorly for tackling marine biodiversity loss and avoiding an Anthropocene mass extinction.

Cetacean fauna of the southern part of the Barents Sea in winter 2019–2023 under changing climate conditions

Biophysical changes occurring in Arctic marine ecosystems under the influence of climatic factors may affect cetaceans staying here. For this reason, the urgent task is to conduct regular monitoring of marine mammals in order to assess the state of their populations and preserve the biodiversity of species. We analyzed the results of ship-based surveys of marine mammals carried out by the Polar branch of VNIRO in January–March 2019–2023 in the south of the Barents Sea and compared them with the observation data of earlier years. As the studies have shown, the winter cetacean fauna is currently represented by six species of baleen Mysticeti and toothed Odontoceti whales. White-beaked dolphin Lagenorhynchus albirostris Gray, 1846 was the most abundant and widespread species among all cetaceans; however, since 2022 we have seen a decrease in both the number of observations and abundance of this species. Fin whale Balaenoptera physalus Linnaeus, 1758 and killer whale Orcinus orca Linnaeus, 1758 were regularly registered in the study area, while sightings of harbor porpoise Phocoena phocoena Linnaeus, 1758 and humpback whale Megaptera novaeangliae Borowski, 1781 were single. Comparative analysis of the obtained data with the materials of 2012–2013 revealed some changes in the cetacean fauna that occurred during the last decade. In the waters of the southern part of the Barents Sea, there began met species that had not been previously recorded in our surveys, first of all, minke whale Balaenoptera acutorostrata Lacépède, 1804 and humpback whale. The materials we collected expanded our understanding of cetaceans staying in the western sector of the Russian Arctic during the winter.

The evolution of menopause in toothed whales

Understanding how and why menopause has evolved is a long-standing challenge across disciplines. Females can typically maximize their reproductive success by reproducing for the whole of their adult life. In humans, however, women cease reproduction several decades before the end of their natural lifespan1,2. Although progress has been made in understanding the adaptive value of menopause in humans3,4, the generality of these findings remains unclear. Toothed whales are the only mammal taxon in which menopause has evolved several times5, providing a unique opportunity to test the theories of how and why menopause evolves in a comparative context. Here, we assemble and analyse a comparative database to test competing evolutionary hypotheses. We find that menopause evolved in toothed whales by females extending their lifespan without increasing their reproductive lifespan, as predicted by the ‘live-long’ hypotheses. We further show that menopause results in females increasing their opportunity for intergenerational help by increasing their lifespan overlap with their grandoffspring and offspring without increasing their reproductive overlap with their daughters. Our results provide an informative comparison for the evolution of human life history and demonstrate that the same pathway that led to menopause in humans can also explain the evolution of menopause in toothed whales.

Directional soundscapes in the Norwegian Seas observed with a coherent hydrophone array

Directional soundscaping is an efficient approach for examining marine ecosystems since it allows the study of living organisms, their behavior, and temporo-spatial interactions with other natural and man-made objects underwater, useful for ecosystem monitoring during offshore energy activities, maritime surveillance, and defense. A large aperture coherent hydrophone array was employed for remote sensing in the Norwegian and Barents Seas in Spring 2014. Extensive analysis have been conducted in post-processing of recorded hydrophone array data for automatic detection, bearing estimation, and classification of signals by different sound producers, such as whale calls, ship radiated noise, and fish sounds. Directional soundscaping through passive ocean acoustic waveguide remote sensing (POAWRS) provides bearing-time trajectories of signal detections that can be applied for geographical mapping. The received marine mammal sounds include vocalizations from baleen whales such as humpback, fin, and minke, and toothed whales, such as beluga, pilot, and sperm. We provide an insight to the vocalizations and behaviorial patterns of these whales in the Lofoten and Northern Finmark regions. The relative contributions of distinct sound sources, including whales, fish, and ships, to the directional soundscapes are quantified. We also examine their temporo-spatial dependences via geographic mapping of acoustic signals from distinct sound producers.