The departure of sperm whales (Physeter macrocephalus) in response to the declining jumbo squid (Dosidicus gigas) population in the central portion of the Gulf of California.

As sperm whales are important predators that control energy flux in the oceans, changes in their population can be used as a sentinel to measure of ecosystem health. The present study conducted a sperm whale survey of the eastern Midriff Islands Region in the Gulf of California over the course of nine years, recording sightings and collecting photographs of the fluke of sperm whale individuals. A photo-identification catalog was compiled, while individual recapture data were used to estimate the population size in the central portion of the Gulf of California, using a Jolly-Seber POPAN open population model. The results obtained show a yearly population of between 20 and 167 sperm whales, with a super population of 354 sperm whales observed between 2009 and 2015. However, from 2016 to 2018, no sightings of the species were recorded, which coincides with the decline observed in landings of their main prey, the jumbo squid, in the region. General additive model conducted on sperm whale sightings per unit of effort vs jumbo squid landings obtained an adjusted R2 of 0.644 and a deviance explained of 60.3%, indicating a good non-linear relationship between sightings of this odontocete and its prey availability. This evidence suggests that sperm whales departed the region between 2016 and 2018, due to a documented fishery collapse alongside changes of their main prey into its small phenotype, possibly as the result of increase warming conditions in surface and subsurface waters in the Gulf of California in the last three decades.

Reinforcement learning-based framework for whale rendezvous via autonomous sensing robots.

Rendezvous with sperm whales for biological observations is made challenging by their prolonged dive patterns. Here, we propose an algorithmic framework that codevelops multiagent reinforcement learning-based routing (autonomy module) and synthetic aperture radar-based very high frequency (VHF) signal-based bearing estimation (sensing module) for maximizing rendezvous opportunities of autonomous robots with sperm whales. The sensing module is compatible with low-energy VHF tags commonly used for tracking wildlife. The autonomy module leverages in situ noisy bearing measurements of whale vocalizations, VHF tags, and whale dive behaviors to enable time-critical rendezvous of a robot team with multiple whales in simulation. We conducted experiments at sea in the native habitat of sperm whales using an "engineered whale"-a speedboat equipped with a VHF-emitting tag, emulating five distinct whale tracks, with different whale motions. The sensing module shows a median bearing error of 10.55° to the tag. Using bearing measurements to the engineered whale from an acoustic sensor and our sensing module, our autonomy module gives an aggregate rendezvous success rate of 81.31% for a 500-meter rendezvous distance using three robots in postprocessing. A second class of fielded experiments that used acoustic-only bearing measurements to three untagged sperm whales showed an aggregate rendezvous success rate of 68.68% for a 1000-meter rendezvous distance using two robots in postprocessing. We further validated these algorithms with several ablation studies using a sperm whale visual encounter dataset collected by marine biologists.

AI-driven aerial robots advance whale research.

Aerial robots assisted with artificial intelligence improve real-time wildlife monitoring of sperm whales.

Passive acoustic surveys demonstrate high densities of sperm whales off the mid-Atlantic coast of the USA in winter and spring.

Oceans are increasingly crowded by anthropogenic activities yet the impact on Outer Continental Shelf (OCS) marine life remains largely unquantified. The MAPS (Marine Mammal Acoustic and Spatial Ecology) study of 2019 included passive acoustic and visual vessel surveys over the Mid-Atlantic OCS of the USA to address data gaps in winter/spring for deep-diving cetaceans, including sperm whales. Echolocation clicks were used to derive slant ranges to sperm whales for design- and model-based density estimates. Although more survey effort was realised in the spring, high densities of whales were identified in both winter and spring (10.46 and 8.89 per 1000 km2 respectively). The spring model-based abundance estimate of 1587 whales (CI 946-2663) was considered the most representative figure, in part due to lower coefficients of variation. Modelling suggested that high densities of whales were associated with warm core rings, eddies and edges. As OCS waters provide an important foraging habitat for North Atlantic sperm whales, appropriate mitigation is required to ensure commercial pressures to develop offshore energy do not negatively affect this endangered species.

Repurposing myoglobin into a carbene transferase for a [2,3]-sigmatropic Sommelet-Hauser rearrangement.

New-to-Nature biocatalysis has emerged as a promising tool in organic synthesis thanks to progress in protein engineering. Notably, hemeproteins have been evolved into robust catalysts for carbene and nitrene transfers and related sigmatropic rearrangements. In this work, we report the first example of a [2,3]-sigmatropic Sommelet-Hauser rearrangement initiated by a carbene transfer of the sperm whale myoglobin mutant L29S,H64V,V68F that was previously reported to catalyze the mechanistically similar [2,3]-sigmatropic Doyle-Kirmse rearrangement. This repurposed heme enzyme catalyzes the Sommelet-Hauser rearrangement between ethyl diazoacetate and benzyl thioethers bearing strong electron-withdrawing substituents with good yields and enantiomeric excess. Optimized catalytic conditions in the absence of any reductant led to an increased asymmetric induction with up to 59% enantiomeric excess. This myoglobin mutant is therefore one of the few catalysts for the asymmetric Sommelet-Hauser rearrangement. This work broadens the scope of abiological reactions catalyzed by iron-carbene transferases with a new example of asymmetric sigmatropic rearrangement.

Age and interpulse interval relation from newborn to adult sperm whale (Physeter macrocephalus) off Mauritius.

Sperm whales (Physeter macrocephalus) have been studied for decades, but the development of their clicks during the animal growth is not yet well known. The click they emit during socialization and echolocation contains information about the length of their acoustic organs and, therefore the length of the body through the interpulse interval (IPI). This paper provides the first IPI/age relationship for juvenile male and female sperm whales (Physeter macrocephalus) based on field recordings of individuals whose age is largely known. Across 9 years, audiovisual recordings of a Mauritian sperm whale social unit were carried out. Adult female and juvenile sperm whales were identified and aged. The dataset made from those recordings is publicly available. The interpulse interval was measured for individuals whose ages ranged from 7 days to around 38 years. The growth of the acoustic organ of juveniles showed an early inter-individual variability as well as sexual dimorphism. Usual growth models were also fitted, predicting a mean I P I ∞ of 3.5 ms for adults and a physical maturity reached at around 30 years old. The use of passive acoustic monitoring (PAM) is one of the main tools used to study sperm whales. This IPI-age relationship may aid demographic studies on sperm whales by enabling PAM to assess the ages of recorded sperm whales.

Sperm whale demographics in the Gulf of Alaska and Bering Sea/Aleutian Islands: An overlooked female habitat.

Sperm whales exhibit sexual dimorphism and sex-specific latitudinal segregation. Females and their young form social groups and are usually found in temperate and tropical latitudes, while males forage at higher latitudes. Historical whaling data and rare sightings of social groups in high latitude regions of the North Pacific, such as the Gulf of Alaska (GOA) and Bering Sea/Aleutian Islands (BSAI), suggest a more complex distribution than previously understood. Sperm whales are the most sighted and recorded cetacean in marine mammal surveys in these regions but capturing their demographic composition and habitat use has proven challenging. This study detects sperm whale presence using passive acoustic data from seven sites in the GOA and BSAI from 2010 to 2019. Differences in click characteristics between males and females (i.e., inter-click and inter-pulse interval) was used as a proxy for animal size/sex to derive time series of animal detections. Generalized additive models with generalized estimation equations demonstrate how spatiotemporal patterns differ between the sexes. Social groups were present at all recording sites with the largest relative proportion at two seamount sites in the GOA and an island site in the BSAI. We found that the seasonal patterns of presence varied for the sexes and between the sites. Male presence was highest in the summer and lowest in the winter, conversely, social group peak presence was in the winter for the BSAI and in the spring for the GOA region, with the lowest presence in the summer months. This study demonstrates that social groups are not restricted to lower latitudes and capture their present-day habitat use in the North Pacific. It highlights that sperm whale distribution is more complex than accounted for in management protocol and underscores the need for improved understanding of sperm whale demographic composition to better understand the impacts of increasing anthropogenic threats, particularly climate change.

Heard off Heard: Acoustic detections of sperm whales (Physeter macrocephalus) and other cetaceans off Heard Island.

An underwater acoustic recorder was moored off Heard Island from September 2017 through March 2018 to listen for marine mammals. Analysis of data was initially conducted by visual inspection of long-term spectral averages to reveal sounds from sperm whales, Antarctic and pygmy blue whales, fin whales, minke whales, odontocete whistles, and noise from nearby ships. Automated detection of sperm whale clicks revealed they were seldom detected from September through January (n = 35 h) but were detected nearly every day of February and March (n = 684 h). Additional analysis of these detections revealed further diel and demographic patterns.

Comparison of carbon, nitrogen, and oxygen stable isotope ratios and mercury concentrations in muscle tissues of five beaked whale species and sperm whales stranded in Hokkaido, Japan.

We studied δ13C, δ15N and δ18O values, and total mercury (THg) concentrations in muscle samples from deep-sea predators - five beaked whale species and sperm whales - stranded along the coast of Hokkaido, in the north of Japan in 2010 and 2019. The δ13C, δ15N and δ18O values, THg concentrations, and body length (BL) of Stejneger's beaked whales were similar to those of Hubbs' beaked whales, which belong to the same genus. In contrast, δ13C values, THg concentrations, and BL of Sato's beaked whales were markedly different from those of Baird's beaked whales, which belong to the same genus. Stejneger's and Hubbs' beaked whales living around Hokkaido may compete in their ecological niches, whereas Sato's and Baird's beaked whales may segregate their ecological niches. Although Cuvier's beaked whales and sperm whales belong to different genera and their BLs were significantly different, their δ13C and δ15N values were similar, probably because they can dive and stay in deeper waters than other beaked whale species. The δ13C values in combined samples from all whales increased with increasing BL, probably owing to the larger whale species' dietary preference for squid. The δ13C values in combined samples from all whales were positively correlated with THg concentrations, whereas the δ15N values in the combined samples were negatively correlated. The δ18O values in combined samples from most whales tended to be positively correlated with THg concentrations. These correlations may be explained by a higher THg load from deep-sea feeding than from pelagic feeding and by a feeding shift towards lower trophic levels.

Contextual and combinatorial structure in sperm whale vocalisations.

Sperm whales (Physeter macrocephalus) are highly social mammals that communicate using sequences of clicks called codas. While a subset of codas have been shown to encode information about caller identity, almost everything else about the sperm whale communication system, including its structure and information-carrying capacity, remains unknown. We show that codas exhibit contextual and combinatorial structure. First, we report previously undescribed features of codas that are sensitive to the conversational context in which they occur, and systematically controlled and imitated across whales. We call these rubato and ornamentation. Second, we show that codas form a combinatorial coding system in which rubato and ornamentation combine with two context-independent features we call rhythm and tempo to produce a large inventory of distinguishable codas. Sperm whale vocalisations are more expressive and structured than previously believed, and built from a repertoire comprising nearly an order of magnitude more distinguishable codas. These results show context-sensitive and combinatorial vocalisation can appear in organisms with divergent evolutionary lineage and vocal apparatus.

Understanding the relationship between the Bering Sea Cold Pool and vocal presence of odontocetes in the context of climate changea).

The Cold Pool is a subsurface layer with water temperatures below 2 °C that is formed in the eastern Bering Sea. This oceanographic feature of relatively cooler bottom temperature impacts zooplankton and forage fish dynamics, driving different energetic pathways dependent upon Bering Sea climatic regime. Odontocetes echolocate to find prey, so tracking foraging vocalizations acoustically provides information to understand the implications of climate change on Cold Pool variability influencing regional food web processes. Vocal foraging dynamics of ice-associated and seasonally migrant marine mammal species suggest that sperm whales spend more time searching for prey in warm years when the Cold Pool is reduced but are more successful at capturing prey during cold years when the Cold Pool is stronger. Beluga whale foraging vocal activity was relatively consistent across climate regimes but peaked during the warm regime. Killer whale foraging vocal activity peaked in both warm and cold regimes with indicators of different ecotypes exploiting changing prey conditions across climate regimes. Foraging activity of odontocete apex predators may serve as a sentinel indicator of future ecosystem change related to prey availability that is linked to a diminishing Cold Pool as water temperatures rise and seasonal sea ice decreases due to climate change.

Click detection rate variability of central North Pacific sperm whales from passive acoustic towed arrays.

Passive acoustic monitoring (PAM) is an optimal method for detecting and monitoring cetaceans as they frequently produce sound while underwater. Cue counting, counting acoustic cues of deep-diving cetaceans instead of animals, is an alternative method for density estimation, but requires an average cue production rate to convert cue density to animal density. Limited information about click rates exists for sperm whales in the central North Pacific Ocean. In the absence of acoustic tag data, we used towed hydrophone array data to calculate the first sperm whale click rates from this region and examined their variability based on click type, location, distance of whales from the array, and group size estimated by visual observers. Our findings show click type to be the most important variable, with groups that include codas yielding the highest click rates. We also found a positive relationship between group size and click detection rates that may be useful for acoustic predictions of group size in future studies. Echolocation clicks detected using PAM methods are often the only indicator of deep-diving cetacean presence. Understanding the factors affecting their click rates provides important information for acoustic density estimation.

High Arctic "hotspots" for sperm whales (Physeter macrocephalus) off western and northern Svalbard, Norway, revealed by multi-year Passive Acoustic Monitoring (PAM).

Despite the well-documented, broad global distribution of sperm whales (Physeter macrocephalus), their distributional patterns remain poorly known in Arctic regions, where year-round monitoring is challenging. Adult male sperm whales are known to migrate seasonally between nutrient-rich high latitude waters and low latitude breeding grounds. However, knowledge is limited regarding fine-scale distribution and seasonal presence at high latitudes. To investigate the acoustic occurrence of this vocally active species in the High Arctic of the Northeast Atlantic, this study combined automated and manual click detection methods to analyze passive acoustic data collected at eight locations around the Svalbard Archipelago, Norway, between 2012 and 2021. The results revealed the presence of sperm whales at six recording sites and demonstrated sperm whale "hotspots" in ice-free areas in eastern Fram Strait along the shelf break and close to the west coast of Spitsbergen from May-January, with some variation between years and locations. Although acoustic presence decreased with increasing latitude, even the northern-most location (81° N) recorded sperm whale vocal activity between August and January. This study provides a baseline for sperm whale acoustic presence in the High Arctic, which will be essential in the context of detecting future changes and also for predicting future distribution patterns in the rapidly changing Arctic marine environment.

Stabilization of myoglobin from different species (produced by cellular agriculture) using food-grade natural and synthetic antioxidants.

Cellular agriculture products, like myoglobin, are increasingly used by the food industry to provide desirable sensory properties to plant-based meat substitutes. This study elucidated the physicochemical properties and redox stability of myoglobin from both natural (equine) and cellular agriculture (bovine, sperm whale, and leopard) sources. The electrical characteristics and water-solubility of the different myoglobin samples were measured from pH 2.5 to 8.5. The isoelectric point of the myoglobin samples depended on the species, being pH 5.5 for equine, pH 4.5 for leopard and bovine, and pH 6.5 for sperm whale. All myoglobin samples had a solubility greater than 80% across the entire pH range studied. All myoglobin solutions appeared red and had two peaks in their UV-visible absorbance spectra after one day, which is consistent with oxymyoglobin formation. Equine myoglobin at pH 8 was selected to study its redox and color stability over time, where the oxymyoglobin oxidative status closely paralleled with the redness of the solutions. The effects of antioxidants (ascorbic acid, caffeic acid, catechin, gallic acid, quercetin, taxifolin, Trolox, and 4-methylcatechol) on the redox and color stability (redness) of the equine myoglobin (pH 8.0) was also studied. Antioxidants with low reduction potential values (ascorbic acid and quercetin) were particularly effective at enhancing the color stability of oxymyoglobin. The computational modeling study showed that amino acids on the myoglobin interacted with antioxidants through hydrogen bonds. The insights obtained may have important implications for the use of cellular agriculture to produce myoglobin for food applications.

The active space of sperm whale codas: inter-click information for intra-unit communication.

Sperm whales (Physeter macrocephalus) are social mega-predators who form stable matrilineal units that often associate within a larger vocal clan. Clan membership is defined by sharing a repertoire of coda types consisting of specific temporal spacings of multi-pulsed clicks. It has been hypothesized that codas communicate membership across socially segregated sympatric clans, but others propose that codas are primarily used for behavioral coordination and social cohesion within a closely spaced social unit. Here, we test these hypotheses by combining measures of ambient noise levels and coda click source levels with models of sound propagation to estimate the active space of coda communication. Coda clicks were localized off the island of Dominica with a four- or five-element 80 m vertical hydrophone array, allowing us to calculate the median RMS source levels of 1598 clicks from 444 codas to be 161 dB re. 1 µPa (IQR 153-167), placing codas among the most powerful communication sounds in toothed whales. However, together with measured ambient noise levels, these source levels lead to a median active space of coda communication of ∼4 km, reflecting the maximum footprint of a single foraging sperm whale unit. We conclude that while sperm whale codas may contain information about clan affiliation, their moderate active space shows that codas are not used for long range acoustic communication between units and clans, but likely serve to mediate social cohesion and behavioral transitions in intra-unit communication.

Phthalate contamination in marine mammals off the Norwegian coast.

Phthalates are used in plastics, found throughout the marine environment and have the potential to cause adverse health effects. In the present study, we quantified blubber concentrations of 11 phthalates in 16 samples from stranded and/or free-living marine mammals from the Norwegian coast: the killer whale (Orcinus orca), sperm whale (Physeter macrocephalus), long-finned pilot whale (Globicephala melas), white-beaked dolphin (Lagenorhynchus albirostris), harbour porpoise (Phocoena phocoena), and harbour seal (Phoca vitulina). Five compounds were detected across all samples: benzyl butyl phthalate (BBP; in 50 % of samples), bis(2-ethylhexyl) phthalate (DEHP; 33 %), diisononyl phthalate (DiNP; 33 %), diisobutyl phthalate (DiBP; 19 %), and dioctyl phthalate (DOP; 13 %). Overall, the most contaminated individual was the white-beaked dolphin, whilst the lowest concentrations were measured in the killer whale, sperm whale and long-finned pilot whale. We found no phthalates in the neonate killer whale. The present study is important for future monitoring and management of these toxic compounds.

Archaeological evidence of resource utilisation of the great whales over the past two millennia: A systematic review protocol.

Archaeological faunal remains provide key insights into human societies in the past, alongside information on previous resource utilisation and exploitation of wildlife populations. The great whales (Mysticete and sperm whales) were hunted unsustainably throughout the 16th - 20th centuries (herein defined as the modern period) leading to large population declines and variable recovery patterns among species. Humans have utilised whales as a resource through carcass scavenging for millennia; however, increasing local and regional ethnographic and archaeological evidence suggests that, prior to the modern period, hunting of the great whales was more common than previously thought; impacts of earlier hunting pressures on the population ecology of many whale species remains relatively unknown. Hunting guided by traditional ecological knowledge may have been sustainable and likely originated in societies that also incorporated opportunistic use of stranded individuals. The collation of georeferenced zooarchaeological data of the great whales between the 1st - 20th centuries CE worldwide will provide insight into the timescale and distribution of resource utilisation of the great whales and how this varied within and between societies, and may have changed over time. By comparing regions of known resource utilisation and breeding and feeding grounds of current-day whale populations, this information will subsequently be used to infer regions where whale populations were possibly lost or extirpated prior to detailed historical records. This systematic review protocol also provides a template for archaeologists, ecologists, and historians interested in using faunal remains to infer historical ecology and resource use of wild animal populations. The transparency of our data collection approach provides opportunities for reproducibility and comparability with future datasets.

Notes on stomach contents of pygmy and dwarf sperm whales (Kogia spp.) from around Japan.

The diets of pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales in Japanese waters are poorly known. We report new information on the diets of these two species from these waters based on identifiable hard-part remains recovered from the stomach contents of 29 whales (11 pygmy and 18 dwarf sperm whales) that stranded between 1991 and 2021; those of a further two dwarf sperm whales were empty. The cephalopod (and secondarily fish and crustacean) component of the diets of these 29 whales, based on analysis of identifiable stomach-content remains, is described. The main prey includes cephalopods, represented by 1556 identifiable lower beaks (and 1483 upper beaks), crustaceans (represented by heavily digested, unidentifiable remains), and fishes (as represented by 92 otoliths). Identified prey comprises 30 species from 16 cephalopod families and 5 families from 5 fish orders. Oceanic cephalopods are the main prey of both whale species, particularly Enoploteuthis (Paraenoploteuthis) chunii and Chiroteuthis (Chirothauma) picteti. Prey diversity index values (Shannon-Weaver's diversity index H') are 2.41 for the pygmy sperm whale and 2.66 for the dwarf sperm whale. Although the main cephalopod component in the diets of these two whale species is similar, Pianka's index (0.40), a measure of niche overlap, is not that high, and may be influenced by differences in prey dominance in different feeding areas.

Population structure of pygmy (Kogia breviceps) and dwarf (Kogia sima) sperm whales in the Southern Hemisphere may reflect foraging ecology and dispersal patterns.

Little is known about the biology of pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales as these animals are difficult to observe in the wild. However, both species strand frequently along the South African, Australian and New Zealand coastlines, providing samples for these otherwise inaccessible species. The use of DNA samples from tissue and DNA extracted from historical material, such as teeth and bone, allowed a first analysis of the population structure of both species in the Southern Hemisphere. A 279 base pair consensus region of the mitochondrial cytochrome b gene was sequenced for 96 K. breviceps (53 tissue and 43 teeth or bone samples) and 29 K. sima (3 tissue and 26 teeth or bone samples), and 26 and 12 unique haplotypes were identified, respectively. K. breviceps showed a higher nucleotide diversity of 0.82% compared to 0.40% in K. sima. Significant genetic differentiation was detected in the Southern Hemisphere between K. breviceps from South Africa and New Zealand (ФST = 0.042, p < 0.05). Mitochondrial control region sequences (505 bp) were available for 44 individuals (41 K. breviceps and 3 K. sima) for comparative purposes. A comprehensive global phylogenetic analysis (maternal lineage) of our sequences together with all available Kogia mtDNA sequences largely supported previously published phylogenetic findings, but highlighted some changed inferences about oceanic divergences within both species. The higher nucleotide diversity and low population differentiation observed in K. breviceps may result from its broad foraging ecology and wide distribution, which may indicate a more opportunistic feeding behaviour and tolerance towards a larger range of water temperatures than K. sima.

Combining passive acoustic data from a towed hydrophone array with visual line transect data to estimate abundance and availability bias of sperm whales (Physeter macrocephalus).

Visual line transect (VLT) surveys are central to the monitoring and study of marine mammals. However, for cryptic species such as deep diving cetaceans VLT surveys alone suffer from problems of low sample sizes and availability bias where animals below the surface are not available to be detected. The advent of passive acoustic monitoring (PAM) technology offers important opportunities to observe deep diving cetaceans but statistical challenges remain particularly when trying to integrate VLT and PAM data. Herein, we present a general framework to combine these data streams to estimate abundance when both surveys are conducted simultaneously. Secondarily, our approach can also be used to derive an estimate of availability bias. We outline three methods that vary in complexity and data requirements which are (1) a simple distance sampling (DS) method that treats the two datasets independently (DS-DS Method), (2) a fully integrated approach that applies a capture-mark recapture (CMR) analysis to the PAM data (CMR-DS Method) and (3) a hybrid approach that requires only a subset of the PAM CMR data (Hybrid Method). To evaluate their performance, we use simulations based on known diving and vocalizing behavior of sperm whales (Physeter macrocephalus). As a case study, we applied the Hybrid Method to data from a shipboard survey of sperm whales and compared estimates to a VLT only analysis. Simulation results demonstrated that the CMR-DS Method and Hybrid Method reduced bias by >90% for both abundance and availability bias in comparison to the simpler DS -DS Method. Overall, the CMR-DS Method was the least biased and most precise. For the case study, our application of the Hybrid Method to the sperm whale dataset produced estimates of abundance and availability bias that were comparable to estimates from the VLT only analysis but with considerably higher precision. Integrating multiple sources of data is an important goal with clear benefits. As a step towards that goal we have developed a novel framework. Results from this study are promising although challenges still remain. Future work may focus on applying this method to other deep-diving species and comparing the proposed method to other statistical approaches that aim to combine information from multiple data sources.